[PATCH 2.6.16.29 1/1] memory: enhance Linux swap subsystem
From: yunfeng zhang
Date: Tue Dec 26 2006 - 03:18:51 EST
In the patch, I introduce a new page system -- pps which can improve
Linux swap subsystem performance, you can find a new document in
Documentation/vm_pps.txt. In brief, swap subsystem should scan/reclaim
pages on VMA instead of zone::active list ...
--- patch-linux/fs/exec.c 2006-12-26 15:20:02.683546016 +0800
+++ linux-2.6.16.29/fs/exec.c 2006-09-13 02:02:10.000000000 +0800
@@ -323,0 +324 @@
+ lru_cache_add_active(page);
@@ -438 +438,0 @@
- enter_pps(mm, mpnt);
--- patch-linux/mm/swap_state.c 2006-12-26 15:20:02.689545104 +0800
+++ linux-2.6.16.29/mm/swap_state.c 2006-09-13 02:02:10.000000000 +0800
@@ -357,2 +357 @@
- if (vma == NULL || !(vma->vm_flags & VM_PURE_PRIVATE))
- lru_cache_add_active(new_page);
+ lru_cache_add_active(new_page);
--- patch-linux/mm/mmap.c 2006-12-26 15:20:02.691544800 +0800
+++ linux-2.6.16.29/mm/mmap.c 2006-09-13 02:02:10.000000000 +0800
@@ -209 +208,0 @@
- leave_pps(vma, 0);
@@ -597 +595,0 @@
- leave_pps(next, 0);
@@ -1096,2 +1093,0 @@
- enter_pps(mm, vma);
-
@@ -1120 +1115,0 @@
- leave_pps(vma, 0);
@@ -1148 +1142,0 @@
- leave_pps(vma, 0);
@@ -1726,4 +1719,0 @@
- if (new->vm_flags & VM_PURE_PRIVATE) {
- new->vm_flags &= ~VM_PURE_PRIVATE;
- enter_pps(mm, new);
- }
@@ -1930 +1919,0 @@
- enter_pps(mm, vma);
@@ -2054,4 +2042,0 @@
- if (new_vma->vm_flags & VM_PURE_PRIVATE) {
- new_vma->vm_flags &= ~VM_PURE_PRIVATE;
- enter_pps(mm, new_vma);
- }
--- patch-linux/mm/fremap.c 2006-12-26 15:20:02.695544192 +0800
+++ linux-2.6.16.29/mm/fremap.c 2006-09-13 02:02:10.000000000 +0800
@@ -40 +40 @@
- if (pte_swapped(pte))
+ if (!pte_file(pte))
--- patch-linux/mm/rmap.c 2006-12-26 15:20:02.696544040 +0800
+++ linux-2.6.16.29/mm/rmap.c 2006-09-13 02:02:10.000000000 +0800
@@ -636 +636 @@
- BUG_ON(!pte_swapped(*pte));
+ BUG_ON(pte_file(*pte));
--- patch-linux/mm/vmscan.c 2006-12-26 15:20:02.697543888 +0800
+++ linux-2.6.16.29/mm/vmscan.c 2006-09-13 02:02:10.000000000 +0800
@@ -1517,392 +1516,0 @@
-struct series_t {
- pte_t orig_ptes[MAX_SERIES_LENGTH];
- pte_t* ptes[MAX_SERIES_LENGTH];
- struct page* pages[MAX_SERIES_LENGTH];
- int series_length;
- int series_stage;
-} series;
-
-static int get_series_stage(pte_t* pte, int index)
-{
- series.orig_ptes[index] = *pte;
- series.ptes[index] = pte;
- if (pte_present(series.orig_ptes[index])) {
- struct page* page = pfn_to_page(pte_pfn(series.orig_ptes[index]));
- series.pages[index] = page;
- if (page == ZERO_PAGE(addr)) // reserved page is exclusive from us.
- return 7;
- if (pte_young(series.orig_ptes[index])) {
- return 1;
- } else
- return 2;
- } else if (pte_unmapped(series.orig_ptes[index])) {
- struct page* page = pfn_to_page(pte_pfn(series.orig_ptes[index]));
- series.pages[index] = page;
- if (!PageSwapCache(page))
- return 3;
- else {
- if (PageWriteback(page) || PageDirty(page))
- return 4;
- else
- return 5;
- }
- } else // pte_swapped -- SwappedPTE
- return 6;
-}
-
-static void find_series(pte_t** start, unsigned long* addr, unsigned long end)
-{
- int i;
- int series_stage = get_series_stage((*start)++, 0);
- *addr += PAGE_SIZE;
-
- for (i = 1; i < MAX_SERIES_LENGTH && *addr < end; i++, (*start)++,
*addr += PAGE_SIZE) {
- if (series_stage != get_series_stage(*start, i))
- break;
- }
- series.series_stage = series_stage;
- series.series_length = i;
-}
-
-struct delay_tlb_task_t delay_tlb_tasks[32] = { [0 ... 31] = {0} };
-
-void timer_flush_tlb_tasks(void* data)
-{
- // To x86, if we found there were some flushing tasks, we should do
it all together, that is, flush it once.
- int i;
-#ifdef CONFIG_X86
- int flag = 0;
-#endif
- for (i = 0; i < 32; i++) {
- if (delay_tlb_tasks[i].mm != NULL &&
- cpu_isset(smp_processor_id(), delay_tlb_tasks[i].mm->cpu_vm_mask) &&
- cpu_isset(smp_processor_id(), delay_tlb_tasks[i].cpu_mask)) {
-#ifdef CONFIG_X86
- flag = 1;
-#elif
- // smp::local_flush_tlb_range(delay_tlb_tasks[i]);
-#endif
- cpu_clear(smp_processor_id(), delay_tlb_tasks[i].cpu_mask);
- }
- }
-#ifdef CONFIG_X86
- if (flag)
- local_flush_tlb();
-#endif
-}
-
-static struct delay_tlb_task_t* delay_task = NULL;
-static int vma_index = 0;
-
-static struct delay_tlb_task_t* search_free_tlb_tasks_slot(void)
-{
- struct delay_tlb_task_t* ret = NULL;
- int i;
-again:
- for (i = 0; i < 32; i++) {
- if (delay_tlb_tasks[i].mm != NULL) {
- if (cpus_empty(delay_tlb_tasks[i].cpu_mask)) {
- mmput(delay_tlb_tasks[i].mm);
- delay_tlb_tasks[i].mm = NULL;
- ret = &delay_tlb_tasks[i];
- }
- } else
- ret = &delay_tlb_tasks[i];
- }
- if (!ret) { // Force flush TLBs.
- on_each_cpu(timer_flush_tlb_tasks, NULL, 0, 1);
- goto again;
- }
- return ret;
-}
-
-static void init_delay_task(struct mm_struct* mm)
-{
- cpus_clear(delay_task->cpu_mask);
- vma_index = 0;
- delay_task->mm = mm;
-}
-
-/*
- * We will be working on the mm, so let's force to flush it if necessary.
- */
-static void start_tlb_tasks(struct mm_struct* mm)
-{
- int i, flag = 0;
-again:
- for (i = 0; i < 32; i++) {
- if (delay_tlb_tasks[i].mm == mm) {
- if (cpus_empty(delay_tlb_tasks[i].cpu_mask)) {
- mmput(delay_tlb_tasks[i].mm);
- delay_tlb_tasks[i].mm = NULL;
- } else
- flag = 1;
- }
- }
- if (flag) { // Force flush TLBs.
- on_each_cpu(timer_flush_tlb_tasks, NULL, 0, 1);
- goto again;
- }
- BUG_ON(delay_task != NULL);
- delay_task = search_free_tlb_tasks_slot();
- init_delay_task(mm);
-}
-
-static void end_tlb_tasks(void)
-{
- if (!cpus_empty(delay_task->cpu_mask)) {
- atomic_inc(&delay_task->mm->mm_users);
- delay_task->cpu_mask = delay_task->mm->cpu_vm_mask;
- } else
- delay_task->mm = NULL;
- delay_task = NULL;
-}
-
-static void fill_in_tlb_tasks(struct vm_area_struct* vma, unsigned long addr,
- unsigned long end)
-{
- struct mm_struct* mm;
-fill_it:
- if (vma_index != 32) {
- delay_task->vma[vma_index] = vma;
- delay_task->start[vma_index] = addr;
- delay_task->end[vma_index] = end;
- vma_index++;
- return;
- }
- mm = delay_task->mm;
- end_tlb_tasks();
-
- delay_task = search_free_tlb_tasks_slot();
- init_delay_task(mm);
- goto fill_it;
-}
-
-static void shrink_pvma_scan_ptes(struct scan_control* sc,
- struct mm_struct* mm, struct vm_area_struct* vma, pmd_t* pmd,
- unsigned long addr, unsigned long end)
-{
- int i;
- spinlock_t* ptl = pte_lockptr(mm, pmd);
- pte_t* pte = pte_offset_map(pmd, addr);
- int anon_rss = 0;
- struct pagevec freed_pvec;
- int may_enter_fs = (sc->gfp_mask & (__GFP_FS | __GFP_IO));
- struct address_space* mapping = &swapper_space;
-
- pagevec_init(&freed_pvec, 1);
- do {
- memset(&series, 0, sizeof(struct series_t));
- find_series(&pte, &addr, end);
- switch (series.series_stage) {
- case 1: // PTE -- untouched PTE.
- for (i = 0; i < series.series_length; i++) {
- struct page* page = series.pages[i];
- lock_page(page);
- spin_lock(ptl);
- if (unlikely(pte_same(*series.ptes[i], series.orig_ptes[i]))) {
- if (pte_dirty(*series.ptes[i]))
- set_page_dirty(page);
- set_pte_at(mm, addr + i * PAGE_SIZE, series.ptes[i],
- pte_mkold(pte_mkclean(*series.ptes[i])));
- }
- spin_unlock(ptl);
- unlock_page(page);
- }
- fill_in_tlb_tasks(vma, addr, addr + (PAGE_SIZE * series.series_length));
- break;
- case 2: // untouched PTE -- UnmappedPTE.
- /*
- * Note in stage 1, we've flushed TLB in fill_in_tlb_tasks, so
- * if it's still clear here, we can shift it to Unmapped type.
- *
- * If some architecture doesn't support atomic cmpxchg
- * instruction or can't atomically set the access bit after
- * they touch a pte at first, combine stage 1 with stage 2, and
- * send IPI immediately in fill_in_tlb_tasks.
- */
- spin_lock(ptl);
- for (i = 0; i < series.series_length; i++) {
- if (unlikely(pte_same(*series.ptes[i], series.orig_ptes[i]))) {
- pte_t pte_unmapped = series.orig_ptes[i];
- pte_unmapped.pte_low &= ~_PAGE_PRESENT;
- pte_unmapped.pte_low |= _PAGE_UNMAPPED;
- if (cmpxchg(&series.ptes[i]->pte_low,
- series.orig_ptes[i].pte_low,
- pte_unmapped.pte_low) !=
- series.orig_ptes[i].pte_low)
- continue;
- page_remove_rmap(series.pages[i]);
- anon_rss--;
- }
- }
- spin_unlock(ptl);
- break;
- case 3: // Attach SwapPage to PrivatePage.
- /*
- * A better arithmetic should be applied to Linux SwapDevice to
- * allocate fake continual SwapPages which are close to each
- * other, the offset between two close SwapPages is less than 8.
- */
- if (sc->may_swap) {
- for (i = 0; i < series.series_length; i++) {
- lock_page(series.pages[i]);
- if (!PageSwapCache(series.pages[i])) {
- if (!add_to_swap(series.pages[i], GFP_ATOMIC)) {
- unlock_page(series.pages[i]);
- break;
- }
- }
- unlock_page(series.pages[i]);
- }
- }
- break;
- case 4: // SwapPage isn't consistent with PrivatePage.
- /*
- * A mini version pageout().
- *
- * Current swap space can't commit multiple pages together:(
- */
- if (sc->may_writepage && may_enter_fs) {
- for (i = 0; i < series.series_length; i++) {
- struct page* page = series.pages[i];
- int res;
-
- if (!may_write_to_queue(mapping->backing_dev_info))
- break;
- lock_page(page);
- if (!PageDirty(page) || PageWriteback(page)) {
- unlock_page(page);
- continue;
- }
- clear_page_dirty_for_io(page);
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .nr_to_write = SWAP_CLUSTER_MAX,
- .nonblocking = 1,
- .for_reclaim = 1,
- };
- page_cache_get(page);
- SetPageReclaim(page);
- res = swap_writepage(page, &wbc);
- if (res < 0) {
- handle_write_error(mapping, page, res);
- ClearPageReclaim(page);
- page_cache_release(page);
- break;
- }
- if (!PageWriteback(page))
- ClearPageReclaim(page);
- page_cache_release(page);
- }
- }
- break;
- case 5: // UnmappedPTE -- SwappedPTE, reclaim PrivatePage.
- for (i = 0; i < series.series_length; i++) {
- struct page* page = series.pages[i];
- lock_page(page);
- spin_lock(ptl);
- if (unlikely(pte_same(*series.ptes[i], series.orig_ptes[i]))) {
- spin_unlock(ptl);
- unlock_page(page);
- continue;
- }
- swp_entry_t entry = { .val = page_private(page) };
- swap_duplicate(entry);
- pte_t pte_swp = swp_entry_to_pte(entry);
- set_pte_at(mm, addr + i * PAGE_SIZE, series.ptes[i], pte_swp);
- spin_unlock(ptl);
- if (PageSwapCache(page) && !PageWriteback(page))
- delete_from_swap_cache(page);
- unlock_page(page);
-
- if (!pagevec_add(&freed_pvec, page))
- __pagevec_release_nonlru(&freed_pvec);
- sc->nr_reclaimed++;
- }
- break;
- case 6:
- // NULL operation!
- break;
- }
- } while (addr < end);
- add_mm_counter(mm, anon_rss, anon_rss);
- if (pagevec_count(&freed_pvec))
- __pagevec_release_nonlru(&freed_pvec);
-}
-
-static void shrink_pvma_pmd_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma, pud_t* pud,
- unsigned long addr, unsigned long end)
-{
- unsigned long next;
- pmd_t* pmd = pmd_offset(pud, addr);
- do {
- next = pmd_addr_end(addr, end);
- if (pmd_none_or_clear_bad(pmd))
- continue;
- shrink_pvma_scan_ptes(sc, mm, vma, pmd, addr, next);
- } while (pmd++, addr = next, addr != end);
-}
-
-static void shrink_pvma_pud_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma, pgd_t* pgd,
- unsigned long addr, unsigned long end)
-{
- unsigned long next;
- pud_t* pud = pud_offset(pgd, addr);
- do {
- next = pud_addr_end(addr, end);
- if (pud_none_or_clear_bad(pud))
- continue;
- shrink_pvma_pmd_range(sc, mm, vma, pud, addr, next);
- } while (pud++, addr = next, addr != end);
-}
-
-static void shrink_pvma_pgd_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma)
-{
- unsigned long next;
- unsigned long addr = vma->vm_start;
- unsigned long end = vma->vm_end;
- pgd_t* pgd = pgd_offset(mm, addr);
- do {
- next = pgd_addr_end(addr, end);
- if (pgd_none_or_clear_bad(pgd))
- continue;
- shrink_pvma_pud_range(sc, mm, vma, pgd, addr, next);
- } while (pgd++, addr = next, addr != end);
-}
-
-static void shrink_private_vma(struct scan_control* sc)
-{
- struct mm_struct* mm;
- struct vm_area_struct* vma;
- struct list_head *pos, *lhtemp;
-
- spin_lock(&mmlist_lock);
- list_for_each_safe(pos, lhtemp, &init_mm.mmlist) {
- mm = list_entry(pos, struct mm_struct, mmlist);
- if (atomic_inc_return(&mm->mm_users) == 1) {
- atomic_dec(&mm->mm_users);
- continue;
- }
- spin_unlock(&mmlist_lock);
- start_tlb_tasks(mm);
- if (down_read_trylock(&mm->mmap_sem)) {
- for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
- if (!(vma->vm_flags & VM_PURE_PRIVATE))
- continue;
- if (vma->vm_flags & VM_LOCKED)
- continue;
- shrink_pvma_pgd_range(sc, mm, vma);
- }
- up_read(&mm->mmap_sem);
- }
- end_tlb_tasks();
- mmput(mm);
- spin_lock(&mmlist_lock);
- }
- spin_unlock(&mmlist_lock);
-}
-
@@ -1952 +1559,0 @@
- shrink_private_vma(&sc);
--- patch-linux/mm/swapfile.c 2006-12-26 15:20:02.699543584 +0800
+++ linux-2.6.16.29/mm/swapfile.c 2006-09-13 02:02:10.000000000 +0800
@@ -10 +9,0 @@
-#include <linux/mm_inline.h>
@@ -421,157 +419,0 @@
-static int pps_test_swap_type(struct mm_struct* mm, pmd_t* pmd, pte_t* pte, int
- type, struct page** ret_page)
-{
- spinlock_t* ptl = pte_lockptr(mm, pmd);
- swp_entry_t entry;
- struct page* page;
-
- spin_lock(ptl);
- if (!pte_present(*pte) && pte_swapped(*pte)) {
- entry = pte_to_swp_entry(*pte);
- if (swp_type(entry) == type) {
- *ret_page = NULL;
- spin_unlock(ptl);
- return 1;
- }
- } else {
- page = pfn_to_page(pte_pfn(*pte));
- if (PageSwapCache(page)) {
- entry.val = page_private(page);
- if (swp_type(entry) == type) {
- page_cache_get(page);
- *ret_page = page;
- spin_unlock(ptl);
- return 1;
- }
- }
- }
- spin_unlock(ptl);
- return 0;
-}
-
-static int pps_swapoff_scan_ptes(struct mm_struct* mm, struct vm_area_struct*
- vma, pmd_t* pmd, unsigned long addr, unsigned long end, int type)
-{
- pte_t *pte;
- struct page* page;
-
- pte = pte_offset_map(pmd, addr);
- do {
- while (pps_test_swap_type(mm, pmd, pte, type, &page)) {
- if (page == NULL) {
- switch (__handle_mm_fault(mm, vma, addr, 0)) {
- case VM_FAULT_SIGBUS:
- case VM_FAULT_OOM:
- return -ENOMEM;
- case VM_FAULT_MINOR:
- case VM_FAULT_MAJOR:
- break;
- default:
- BUG();
- }
- } else {
- wait_on_page_locked(page);
- wait_on_page_writeback(page);
- lock_page(page);
- if (!PageSwapCache(page)) {
- unlock_page(page);
- page_cache_release(page);
- break;
- }
- wait_on_page_writeback(page);
- delete_from_swap_cache(page);
- unlock_page(page);
- page_cache_release(page);
- break;
- }
- }
- } while (pte++, addr += PAGE_SIZE, addr != end);
- return 0;
-}
-
-static int pps_swapoff_pmd_range(struct mm_struct* mm, struct vm_area_struct*
- vma, pud_t* pud, unsigned long addr, unsigned long end, int type)
-{
- unsigned long next;
- int ret;
- pmd_t* pmd = pmd_offset(pud, addr);
- do {
- next = pmd_addr_end(addr, end);
- if (pmd_none_or_clear_bad(pmd))
- continue;
- ret = pps_swapoff_scan_ptes(mm, vma, pmd, addr, next, type);
- if (ret == -ENOMEM)
- return ret;
- } while (pmd++, addr = next, addr != end);
- return 0;
-}
-
-static int pps_swapoff_pud_range(struct mm_struct* mm, struct vm_area_struct*
- vma, pgd_t* pgd, unsigned long addr, unsigned long end, int type)
-{
- unsigned long next;
- int ret;
- pud_t* pud = pud_offset(pgd, addr);
- do {
- next = pud_addr_end(addr, end);
- if (pud_none_or_clear_bad(pud))
- continue;
- ret = pps_swapoff_pmd_range(mm, vma, pud, addr, next, type);
- if (ret == -ENOMEM)
- return ret;
- } while (pud++, addr = next, addr != end);
- return 0;
-}
-
-static int pps_swapoff_pgd_range(struct mm_struct* mm, struct vm_area_struct*
- vma, int type)
-{
- unsigned long next;
- unsigned long addr = vma->vm_start;
- unsigned long end = vma->vm_end;
- int ret;
- pgd_t* pgd = pgd_offset(mm, addr);
- do {
- next = pgd_addr_end(addr, end);
- if (pgd_none_or_clear_bad(pgd))
- continue;
- ret = pps_swapoff_pud_range(mm, vma, pgd, addr, next, type);
- if (ret == -ENOMEM)
- return ret;
- } while (pgd++, addr = next, addr != end);
- return 0;
-}
-
-static int pps_swapoff(int type)
-{
- struct mm_struct* mm;
- struct vm_area_struct* vma;
- struct list_head *pos, *lhtemp;
- int ret = 0;
-
- spin_lock(&mmlist_lock);
- list_for_each_safe(pos, lhtemp, &init_mm.mmlist) {
- mm = list_entry(pos, struct mm_struct, mmlist);
- if (atomic_inc_return(&mm->mm_users) == 1) {
- atomic_dec(&mm->mm_users);
- continue;
- }
- spin_unlock(&mmlist_lock);
- down_read(&mm->mmap_sem);
- for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
- if (!(vma->vm_flags & VM_PURE_PRIVATE))
- continue;
- if (vma->vm_flags & VM_LOCKED)
- continue;
- ret = pps_swapoff_pgd_range(mm, vma, type);
- if (ret == -ENOMEM)
- break;
- }
- up_read(&mm->mmap_sem);
- mmput(mm);
- spin_lock(&mmlist_lock);
- }
- spin_unlock(&mmlist_lock);
- return ret;
-}
-
@@ -780,6 +621,0 @@
- // Let's first read all pps pages back! Note, it's one-to-one mapping.
- retval = pps_swapoff(type);
- if (retval == -ENOMEM) // something was wrong.
- return -ENOMEM;
- // Now, the remain pages are shared pages, go ahead!
-
@@ -1015 +851 @@
- // struct list_head *p, *next;
+ struct list_head *p, *next;
@@ -1021,3 +856,0 @@
- /*
- * Now, init_mm.mmlist list not only is used by SwapDevice but also is used
- * by PPS.
@@ -1028 +860,0 @@
- */
--- patch-linux/mm/memory.c 2006-12-26 15:20:02.701543280 +0800
+++ linux-2.6.16.29/mm/memory.c 2006-09-13 02:02:10.000000000 +0800
@@ -439 +439 @@
- if (pte_swapped(pte)) {
+ if (!pte_file(pte)) {
@@ -661,2 +660,0 @@
- // if (vma->vm_flags & VM_PURE_PRIVATE && page != ZERO_PAGE(addr))
- // lru_cache_add_active(page);
@@ -682,10 +680 @@
- if (pte_unmapped(ptent)) {
- struct page *page;
- page = pfn_to_page(pte_pfn(ptent));
- pte_clear_full(mm, addr, pte, tlb->fullmm);
- // lru_cache_add_active(page);
- tlb_remove_page(tlb, page);
- anon_rss--;
- continue;
- }
- if (pte_swapped(ptent))
+ if (!pte_file(ptent))
@@ -1522,2 +1511 @@
- if (!(vma->vm_flags & VM_PURE_PRIVATE))
- lru_cache_add_active(new_page);
+ lru_cache_add_active(new_page);
@@ -1879,78 +1866,0 @@
- * New read ahead code, mainly for VM_PURE_PRIVATE only.
- */
-static void pps_swapin_readahead(swp_entry_t entry, unsigned long
addr,struct vm_area_struct *vma, pte_t* pte, pmd_t* pmd)
-{
- struct page* page;
- pte_t *prev, *next;
- swp_entry_t temp;
- spinlock_t* ptl = pte_lockptr(vma->vm_mm, pmd);
- int swapType = swp_type(entry);
- int swapOffset = swp_offset(entry);
- int readahead = 1, abs;
-
- if (!(vma->vm_flags & VM_PURE_PRIVATE)) {
- swapin_readahead(entry, addr, vma);
- return;
- }
-
- page = read_swap_cache_async(entry, vma, addr);
- if (!page)
- return;
- page_cache_release(page);
-
- // read ahead the whole series, first forward then backward.
- while (readahead < MAX_SERIES_LENGTH) {
- next = pte++;
- if (next - (pte_t*) pmd >= PTRS_PER_PTE)
- break;
- spin_lock(ptl);
- if (!(!pte_present(*next) && pte_swapped(*next))) {
- spin_unlock(ptl);
- break;
- }
- temp = pte_to_swp_entry(*next);
- spin_unlock(ptl);
- if (swp_type(temp) != swapType)
- break;
- abs = swp_offset(temp) - swapOffset;
- abs = abs < 0 ? -abs : abs;
- swapOffset = swp_offset(temp);
- if (abs > 8)
- // the two swap entries are too far, give up!
- break;
- page = read_swap_cache_async(temp, vma, addr);
- if (!page)
- return;
- page_cache_release(page);
- readahead++;
- }
-
- swapOffset = swp_offset(entry);
- while (readahead < MAX_SERIES_LENGTH) {
- prev = pte--;
- if (prev - (pte_t*) pmd < 0)
- break;
- spin_lock(ptl);
- if (!(!pte_present(*prev) && pte_swapped(*prev))) {
- spin_unlock(ptl);
- break;
- }
- temp = pte_to_swp_entry(*prev);
- spin_unlock(ptl);
- if (swp_type(temp) != swapType)
- break;
- abs = swp_offset(temp) - swapOffset;
- abs = abs < 0 ? -abs : abs;
- swapOffset = swp_offset(temp);
- if (abs > 8)
- // the two swap entries are too far, give up!
- break;
- page = read_swap_cache_async(temp, vma, addr);
- if (!page)
- return;
- page_cache_release(page);
- readahead++;
- }
-}
-
-/*
@@ -1978 +1888 @@
- pps_swapin_readahead(entry, address, vma, page_table, pmd);
+ swapin_readahead(entry, address, vma);
@@ -1997,2 +1907 @@
- if (!(vma->vm_flags & VM_PURE_PRIVATE))
- mark_page_accessed(page);
+ mark_page_accessed(page);
@@ -2002,4 +1910,0 @@
- if (vma->vm_flags & VM_PURE_PRIVATE) {
- lru_cache_add_active(page);
- mark_page_accessed(page);
- }
@@ -2020,4 +1924,0 @@
- if (vma->vm_flags & VM_PURE_PRIVATE) {
- lru_cache_add_active(page);
- mark_page_accessed(page);
- }
@@ -2095,2 +1995,0 @@
- if (!(vma->vm_flags & VM_PURE_PRIVATE))
- lru_cache_add_active(page);
@@ -2097,0 +1997 @@
+ lru_cache_add_active(page);
@@ -2312,14 +2211,0 @@
- if (pte_unmapped(entry)) {
- BUG_ON(!(vma->vm_flags & VM_PURE_PRIVATE));
- struct page* page = pte_page(entry);
- pte_t temp_pte = mk_pte(page, vma->vm_page_prot);
- pte = pte_offset_map_lock(mm, pmd, address, &ptl);
- if (unlikely(pte_same(*pte, entry))) {
- page_add_new_anon_rmap(page, vma, address);
- set_pte_at(mm, address, pte, temp_pte);
- update_mmu_cache(vma, address, temp_pte);
- lazy_mmu_prot_update(temp_pte);
- }
- pte_unmap_unlock(pte, ptl);
- return VM_FAULT_MINOR;
- }
@@ -2562,109 +2447,0 @@
-
-static void migrate_back_pte_range(struct mm_struct* mm, pmd_t *pmd, struct
- vm_area_struct *vma, unsigned long addr, unsigned long end)
-{
- struct page* page;
- pte_t entry;
- pte_t* pte;
- spinlock_t* ptl;
-
- pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
- do {
- if (!pte_present(*pte) && pte_unmapped(*pte)) {
- page = pte_page(*pte);
- entry = mk_pte(page, vma->vm_page_prot);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- set_pte_at(mm, addr, pte, entry);
- BUG_ON(page == ZERO_PAGE(addr));
- page_add_new_anon_rmap(page, vma, addr);
- }
- if (pte_present(*pte)) {
- page = pte_page(*pte);
- if (page == ZERO_PAGE(addr))
- continue;
- lru_cache_add_active(page);
- }
- } while (pte++, addr += PAGE_SIZE, addr != end);
- pte_unmap_unlock(pte - 1, ptl);
- lru_add_drain();
-}
-
-static void migrate_back_pmd_range(struct mm_struct* mm, pud_t *pud, struct
- vm_area_struct *vma, unsigned long addr, unsigned long end)
-{
- pmd_t *pmd;
- unsigned long next;
-
- pmd = pmd_offset(pud, addr);
- do {
- next = pmd_addr_end(addr, end);
- if (pmd_none_or_clear_bad(pmd))
- continue;
- migrate_back_pte_range(mm, pmd, vma, addr, next);
- } while (pmd++, addr = next, addr != end);
-}
-
-static void migrate_back_pud_range(struct mm_struct* mm, pgd_t *pgd, struct
- vm_area_struct *vma, unsigned long addr, unsigned long end)
-{
- pud_t *pud;
- unsigned long next;
-
- pud = pud_offset(pgd, addr);
- do {
- next = pud_addr_end(addr, end);
- if (pud_none_or_clear_bad(pud))
- continue;
- migrate_back_pmd_range(mm, pud, vma, addr, next);
- } while (pud++, addr = next, addr != end);
-}
-
-// migrate all pages of pure private vma back to Linux legacy memory
management.
-static void migrate_back_legacy_linux(struct mm_struct* mm, struct
vm_area_struct* vma)
-{
- pgd_t* pgd;
- unsigned long next;
- unsigned long addr = vma->vm_start;
- unsigned long end = vma->vm_end;
-
- pgd = pgd_offset(mm, addr);
- do {
- next = pgd_addr_end(addr, end);
- if (pgd_none_or_clear_bad(pgd))
- continue;
- migrate_back_pud_range(mm, pgd, vma, addr, next);
- } while (pgd++, addr = next, addr != end);
-}
-
-LIST_HEAD(pps_head);
-LIST_HEAD(pps_head_buddy);
-
-DEFINE_SPINLOCK(pps_lock);
-
-void enter_pps(struct mm_struct* mm, struct vm_area_struct* vma)
-{
- int condition = VM_READ | VM_WRITE | VM_EXEC | \
- VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC | \
- VM_GROWSDOWN | VM_GROWSUP | \
- VM_LOCKED | VM_SEQ_READ | VM_RAND_READ | VM_DONTCOPY | VM_ACCOUNT;
- if (!(vma->vm_flags & ~condition) && vma->vm_file == NULL) {
- vma->vm_flags |= VM_PURE_PRIVATE;
- if (list_empty(&mm->mmlist)) {
- spin_lock(&mmlist_lock);
- if (list_empty(&mm->mmlist))
- list_add(&mm->mmlist, &init_mm.mmlist);
- spin_unlock(&mmlist_lock);
- }
- }
-}
-
-void leave_pps(struct vm_area_struct* vma, int migrate_flag)
-{
- struct mm_struct* mm = vma->vm_mm;
-
- if (vma->vm_flags & VM_PURE_PRIVATE) {
- vma->vm_flags &= ~VM_PURE_PRIVATE;
- if (migrate_flag)
- migrate_back_legacy_linux(mm, vma);
- }
-}
--- patch-linux/kernel/timer.c 2006-12-26 15:20:02.688545256 +0800
+++ linux-2.6.16.29/kernel/timer.c 2006-09-13 02:02:10.000000000 +0800
@@ -845,2 +844,0 @@
-
- timer_flush_tlb_tasks(NULL);
--- patch-linux/kernel/fork.c 2006-12-26 15:20:02.688545256 +0800
+++ linux-2.6.16.29/kernel/fork.c 2006-09-13 02:02:10.000000000 +0800
@@ -232 +231,0 @@
- leave_pps(mpnt, 1);
--- patch-linux/Documentation/vm_pps.txt 2006-12-26 15:45:33.203883456 +0800
+++ linux-2.6.16.29/Documentation/vm_pps.txt 1970-01-01 08:00:00.000000000 +0800
@@ -1,190 +0,0 @@
- Pure Private Page System (pps)
- Copyright by Yunfeng Zhang on GFDL 1.2
- zyf.zeroos@xxxxxxxxx
- December 24-26, 2006
-
-// Purpose <([{
-The file is used to document the idea which is published firstly at
-http://www.ussg.iu.edu/hypermail/linux/kernel/0607.2/0451.html, as a part of my
-OS -- main page http://blog.chinaunix.net/u/21764/index.php. You can find the
-overview of the idea in section <How to Reclaim Pages more Efficiently> and how
-I patch it into Linux 2.6.16.29 in section <Pure Private Page System -- pps>.
-// }])>
-
-// How to Reclaim Pages more Efficiently <([{
-Good idea originates from overall design and management ability, when you look
-down from a manager view, you will relief yourself from disordered code and
-find some problem immediately.
-
-OK! to modern OS, its memory subsystem can be divided into three layers
-1) Space layer (InodeSpace, UserSpace and CoreSpace).
-2) VMA layer (PrivateVMA and SharedVMA, memory architecture-independent layer).
-3) PTE and page layer (architecture-dependent).
-
-Since the 2nd layer assembles the much statistic of page-acess information, so
-it's nature that swap subsystem should be deployed and implemented on the 2nd
-layer.
-
-Undoubtedly, there are some virtues about it
-1) SwapDaemon can collect the statistic of process acessing pages and by it
- unmaps ptes, SMP specially benefits from it for we can use flush_tlb_range
- to relief frequently TLB IPI interrupt.
-2) Page-fault can issue better readahead requests since history data shows all
- related pages have conglomerating affinity.
-3) It's conformable to POSIX madvise API family.
-
-Unfortunately, Linux 2.6.16.29 swap subsystem is based on the 3rd layer -- a
-system surrounding page.
-
-I've commited a patch to it, see section <Pure Private Page System --
pps>. Note, it ISN'T perfect.
-// }])>
-
-// Pure Private Page System -- pps <([{
-Current Linux is just like a monster and still growing, even its swap subsystem
-...
-
-As I've referred in previous section, perfectly applying my idea need to unroot
-page-surrounging swap subsystem to migrate it on VMA, but a huge gap has
-defeated me -- active_list and inactive_list. In fact, you can find
-lru_add_active anywhere ... It's IMPOSSIBLE to me to complete it only by
-myself. It's also the difference between my design and Linux, in my OS, page is
-the charge of its new owner totally, however, to Linux, page management system
-is still tracing it by PG_active flag.
-
-So I conceive another solution:) That is, set up an independent page-recycle
-system rooted on Linux legacy page system -- pps, intercept all private pages
-belonging to PrivateVMA to pps, then use my pps to cycle them. By the way, the
-whole job should be consist of two parts, here is the first --
-PrivateVMA-oriented (PPS), other is SharedVMA-oriented (should be called SPS)
-scheduled in future. Of course, if all are done, it will empty Linux legacy
-page system.
-
-In fact, pps is centered on how to better collect and unmap process private
-pages in SwapDaemon mm/vmscan.c:shrink_private_vma, the whole process is
-divided into six stages -- <Stage Definition>. Other sections show the remain
-aspects of pps
-1) <Data Definition> is basic data definition.
-2) <Concurrent racers of Shrinking pps> is focused on synchronization.
-3) <Private Page Lifecycle of pps> -- how private pages enter in/go off pps.
-4) <VMA Lifecycle of pps> which VMA is belonging to pps.
-
-PPS uses init_mm.mm_list list to enumerate all swappable UserSpace.
-
-I'm also glad to highlight my a new idea -- dftlb which is described in
-section <Delay to Flush TLB>.
-// }])>
-
-// Delay to Flush TLB (dftlb) <([{
-Delay to flush TLB is instroduced by me to enhance flushing TLB efficiency, in
-brief, when we want to unmap a page from the page table of a process, why we
-send TLB IPI to other CPUs immediately, since every CPU has timer interrupt, we
-can insert flushing tasks into timer interrupt route to implement a
-free-charged TLB flushing.
-
-The trick is implemented in
-1) TLB flushing task is added in fill_in_tlb_task of mm/vmscan.c.
-2) timer_flush_tlb_tasks of kernel/timer.c is used by other CPUs to execute
- flushing tasks.
-3) all data are defined in include/linux/mm.h.
-
-The restriction of dftlb. Following conditions must be met
-1) atomic cmpxchg instruction.
-2) atomically set the access bit after they touch a pte firstly.
-3) To some architectures, vma parameter of flush_tlb_range is maybe important,
- if it's true, since it's possible that the vma of a TLB flushing task has
- gone when a CPU starts to execute the task in timer interrupt, so don't use
- dftlb.
-combine stage 1 with stage 2, and send IPI immediately in fill_in_tlb_tasks.
-// }])>
-
-// Stage Definition <([{
-The whole process of private page page-out is divided into six stages, as
-showed in shrink_pvma_scan_ptes of mm/vmscan.c
-1) PTE to untouched PTE (access bit is cleared), append flushing
tasks to dftlb.
-2) Convert untouched PTE to UnmappedPTE.
-3) Link SwapEntry to every UnmappedPTE.
-4) Synchronize the page of a UnmappedPTE with its physical swap page.
-5) Reclaimed the page and shift UnmappedPTE to SwappedPTE.
-6) SwappedPTE stage.
-// }])>
-
-// Data Definition <([{
-New VMA flag (VM_PURE_PRIVATE) is appended into VMA in include/linux/mm.h.
-
-New PTE type (UnmappedPTE) is appended into PTE system in
-include/asm-i386/pgtable.h.
-// }])>
-
-// Concurrent Racers of Shrinking pps <([{
-shrink_private_vma of mm/vmscan.c uses init_mm.mmlist to scan all swappable
-mm_struct instances, during the process of scaning and reclaiming process, it
-readlockes every mm_struct object, which brings some potential concurrent
-racers
-1) mm/swapfile.c pps_swapoff (swapoff API).
-2) mm/memory.c do_wp_page, handle_pte_fault::unmapped_pte, do_anonymous_page
- (page-fault).
-// }])>
-
-// Private Page Lifecycle of pps <([{
-All pages belonging to pps are called as pure private page.
-
-IN (NOTE, when a pure private page enters into pps, it's also trimmed from
-Linux legacy page system by commeting lru_cache_add_active clause)
-1) fs/exec.c install_arg_pages (argument pages).
-2) mm/memory do_anonymous_page, do_wp_page, do_swap_page (page fault).
-3) mm/swap_state.c read_swap_cache_async (swap pages).
-
-OUT
-1) mm/vmscan.c shrink_pvma_scan_ptes (stage 6, reclaim a private page).
-2) mm/memory zap_pte_range (free a page).
-3) kernel/fork.c dup_mmap (if someone uses fork, migrate all pps pages
- back to let Linux legacy page system manage them).
-
-When a pure private page is in pps, it can be visited simultaneously by
-page-fault and SwapDaemon.
-// }])>
-
-// VMA Lifecycle of pps <([{
-When a PrivateVMA enters into pps, it's or-ed a new flag -- VM_PURE_PRIVATE,
-the flag is used in the shrink_private_vma of mm/vmscan.c. Other fields are
-reserved untouch state.
-
-IN.
-1) fs/exec.c setup_arg_pages (StackVMA).
-2) mm/mmap.c do_mmap_pgoff, do_brk (DataVMA).
-3) mm/mmap.c split_vma, copy_vma (in some cases, we need copy a VMA from an
- exist VMA).
-
-OUT.
-1) kernel/fork.c dup_mmap (if someone uses fork, return the vma back to
- Linux legacy system).
-2) mm/mmap.c remove_vma, vma_adjust (destroy VMA).
-3) mm/mmap.c do_mmap_pgoff (delete VMA when some errors occur).
-// }])>
-
-// Postscript <([{
-Note, some circumstances aren't tested due to hardware restriction e.g. SMP
-dftlb.
-
-Here are some improvements about pps
-1) In fact, I recommend one-to-one private model -- PrivateVMA, (PTE,
- UnmappedPTE) and PrivatePage which is described in my OS and the aboved
- hyperlink of Linux kernel mail list. So it's a compromise to use Linux
- legacy SwapCache in my pps.
-2) SwapCache should provide more flexible interfaces, shrink_pvma_scan_ptes
- need allocate swap entries in batch, exactly, allocate a batch of fake
- continual swap entries, see mm/pps_swapin_readahead.
-3) pps statistic entry in /proc/meminfo.
-4) a better arithmetic to pick mm out to scan and shrink in shrink_private_vma.
-5) It's better to execute the first 2 stages when system is idle, current
- SwapDaemon only is activated when free pages are low.
-6) A scanning count should be added into mm_struct, so when the count is
- becoming enough old to open stage 3 and 4.
-
-I'm still working on improvement 4, 5 and 6 to find out how to maximum the
-performance of swap subsystem.
-
-If Linux kernel group can't make a schedule to re-write their memory code,
-however, pps maybe is the best solution until now.
-// }])>
-// vim: foldmarker=<([{,}])> foldmethod=marker et
--- patch-linux/include/linux/mm.h 2006-12-26 15:20:02.685545712 +0800
+++ linux-2.6.16.29/include/linux/mm.h 2006-09-13 02:02:10.000000000 +0800
@@ -169,2 +168,0 @@
-#define VM_PURE_PRIVATE 0x04000000 /* Is the vma is only belonging to a mm,
- see more from Documentation/vm_pps.txt */
@@ -1061,18 +1058,0 @@
-/* vmscan.c::delay flush TLB */
-struct delay_tlb_task_t
-{
- struct mm_struct* mm; //__attribute__ ((section(".pure_private_vma.data")));
- cpumask_t cpu_mask;
- struct vm_area_struct* vma[32];
- unsigned long start[32];
- unsigned long end[32];
-};
-extern struct delay_tlb_task_t delay_tlb_tasks[32];
-
-// The prototype of the function is fit with the "func" of "int
smp_call_function (void (*func) (void *info), void *info, int retry,
int wait);" of include/linux/smp.h of 2.6.16.29. Call it with NULL.
-void timer_flush_tlb_tasks(void* data /* = NULL */);
-
-void enter_pps(struct mm_struct* mm, struct vm_area_struct* vma);
-void leave_pps(struct vm_area_struct* vma, int migrate_flag);
-
-#define MAX_SERIES_LENGTH 8
--- patch-linux/include/linux/swapops.h 2006-12-26 15:20:02.686545560 +0800
+++ linux-2.6.16.29/include/linux/swapops.h 2006-09-13 02:02:10.000000000 +0800
@@ -53 +53 @@
- BUG_ON(!pte_swapped(pte));
+ BUG_ON(pte_file(pte));
@@ -67 +67 @@
- BUG_ON(!pte_swapped(__swp_entry_to_pte(arch_entry)));
+ BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
--- patch-linux/include/asm-i386/pgtable-2level.h 2006-12-26
15:20:02.687545408 +0800
+++ linux-2.6.16.29/include/asm-i386/pgtable-2level.h 2006-09-13
02:02:10.000000000 +0800
@@ -49 +49 @@
- * Bits 0, 5, 6 and 7 are taken, split up the 28 bits of offset
+ * Bits 0, 6 and 7 are taken, split up the 29 bits of offset
@@ -52 +52 @@
-#define PTE_FILE_MAX_BITS 28
+#define PTE_FILE_MAX_BITS 29
@@ -55 +55 @@
- ((((pte).pte_low >> 1) & 0xf ) + (((pte).pte_low >> 8) << 4 ))
+ ((((pte).pte_low >> 1) & 0x1f ) + (((pte).pte_low >> 8) << 5 ))
@@ -58 +58 @@
- ((pte_t) { (((off) & 0xf) << 1) + (((off) >> 4) << 8) + _PAGE_FILE })
+ ((pte_t) { (((off) & 0x1f) << 1) + (((off) >> 5) << 8) + _PAGE_FILE })
@@ -61 +61 @@
-#define __swp_type(x) (((x).val >> 1) & 0xf)
+#define __swp_type(x) (((x).val >> 1) & 0x1f)
@@ -63 +63 @@
-#define __swp_entry(type, offset) ((swp_entry_t) { ((type & 0xf) <<
1) | ((offset) << 8) | _PAGE_SWAPPED })
+#define __swp_entry(type, offset) ((swp_entry_t) { ((type) << 1) |
((offset) << 8) })
--- patch-linux/include/asm-i386/pgtable.h 2006-12-26 15:20:02.687545408 +0800
+++ linux-2.6.16.29/include/asm-i386/pgtable.h 2006-09-13
02:02:10.000000000 +0800
@@ -124,5 +124 @@
-#define _PAGE_UNMAPPED 0x020 /* a special PTE type, hold its page reference
- even it's unmapped, see more from
- Documentation/vm_pps.txt. */
-#define _PAGE_SWAPPED 0x040 /* swapped PTE. */
-#define _PAGE_FILE 0x060 /* nonlinear file mapping, saved PTE; */
+#define _PAGE_FILE 0x040 /* nonlinear file mapping, saved PTE; unset:swap */
@@ -235,3 +231 @@
-static inline int pte_unmapped(pte_t pte) { return ((pte).pte_low &
0x60) == _PAGE_UNMAPPED; }
-static inline int pte_swapped(pte_t pte) { return ((pte).pte_low &
0x60) == _PAGE_SWAPPED; }
-static inline int pte_file(pte_t pte) { return ((pte).pte_low &
0x60) == _PAGE_FILE; }
+static inline int pte_file(pte_t pte) { return (pte).pte_low & _PAGE_FILE; }
-
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