Previous discussions of this are at
http://humbolt.nl.linux.org/lists/linux-mm/1999-02/msg00040.html
I ran tests on UP and MP systems with varying amounts of memory to test
the basic working of the patch. I also ran AIM7 on a 4cpu 1200M machine.
The result:
regular 2.2.1 kernel - Peak 1834.7, Sustained 1527.4
patched 2.2.1 kernel - Peak 1926.2, Sustained 1546.8
which is about a 5% improvement in the peak rate.
The patch limits the amount of vmalloc memory for ia32 systems to
VMALLOC_RESERVE (64Mb) on all memory configurations - note that big
memory systems ( ~960 Mb physical, 3Gb user space) already are
constrained to somewhat less than 64Mb vmalloc space.
Could people please try out the patch and let me know of problems/
improvements? I am a newbie to the Linux/open source environment, so
I would appreciate any help with getting the code into the development
tree if there is a perceived benefit.
Thanks.
Kanoj
--- /usr/tmp/p_rdiff_a00Hc5/setup.c Wed Feb 17 12:56:09 1999
+++ arch/i386/kernel/setup.c Wed Feb 17 13:35:43 1999
@@ -39,6 +39,7 @@
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/cobalt.h>
+#include <asm/pgtable.h>
/*
* Machine setup..
@@ -327,7 +328,6 @@
*to = '\0';
*cmdline_p = command_line;
-#define VMALLOC_RESERVE (64 << 20) /* 64MB for vmalloc */
#define MAXMEM ((unsigned long)(-PAGE_OFFSET-VMALLOC_RESERVE))
if (memory_end > MAXMEM)
--- /usr/tmp/p_rdiff_a00HeX/init.c Wed Feb 17 12:56:48 1999
+++ arch/i386/mm/init.c Wed Feb 17 13:35:52 1999
@@ -31,12 +31,6 @@
extern void show_net_buffers(void);
extern unsigned long init_smp_mappings(unsigned long);
-void __bad_pte_kernel(pmd_t *pmd)
-{
- printk("Bad pmd in pte_alloc: %08lx\n", pmd_val(*pmd));
- pmd_val(*pmd) = _KERNPG_TABLE + __pa(BAD_PAGETABLE);
-}
-
void __bad_pte(pmd_t *pmd)
{
printk("Bad pmd in pte_alloc: %08lx\n", pmd_val(*pmd));
@@ -43,28 +37,6 @@
pmd_val(*pmd) = _PAGE_TABLE + __pa(BAD_PAGETABLE);
}
-pte_t *get_pte_kernel_slow(pmd_t *pmd, unsigned long offset)
-{
- pte_t *pte;
-
- pte = (pte_t *) __get_free_page(GFP_KERNEL);
- if (pmd_none(*pmd)) {
- if (pte) {
- clear_page((unsigned long)pte);
- pmd_val(*pmd) = _KERNPG_TABLE + __pa(pte);
- return pte + offset;
- }
- pmd_val(*pmd) = _KERNPG_TABLE + __pa(BAD_PAGETABLE);
- return NULL;
- }
- free_page((unsigned long)pte);
- if (pmd_bad(*pmd)) {
- __bad_pte_kernel(pmd);
- return NULL;
- }
- return (pte_t *) pmd_page(*pmd) + offset;
-}
-
pte_t *get_pte_slow(pmd_t *pmd, unsigned long offset)
{
unsigned long pte;
@@ -211,7 +183,29 @@
}
/*
- * allocate page table(s) for compile-time fixed mappings
+ * allocate kernel page table(s) for vmalloc range, tlb flushed in
+ * paging_init (careful with 32 bit wraparound in while loop)
+ */
+static unsigned long __init kptbl_init(unsigned long start_mem)
+{
+ unsigned long address = VMALLOC_START;
+ pgd_t *dir = pgd_offset_k(address);
+
+ start_mem = PAGE_ALIGN(start_mem);
+ while ((address < VMALLOC_END) && (address >= VMALLOC_START)) {
+ memset((void *)start_mem, 0, PAGE_SIZE);
+ pgd_val(*dir) = _KERNPG_TABLE | __pa(start_mem);
+ address = (address + PGDIR_SIZE) & PGDIR_MASK;
+ dir++;
+ start_mem += PAGE_SIZE;
+ }
+ return start_mem;
+}
+
+/*
+ * allocate page table(s) for compile-time fixed mappings, taking
+ * care not to reallocate a page table if kptbl_init already
+ * allocated one.
*/
static unsigned long __init fixmap_init(unsigned long start_mem)
{
@@ -225,9 +219,11 @@
{
address = __fix_to_virt(__end_of_fixed_addresses-idx);
pg_dir = swapper_pg_dir + (address >> PGDIR_SHIFT);
- memset((void *)start_mem, 0, PAGE_SIZE);
- pgd_val(*pg_dir) = _PAGE_TABLE | __pa(start_mem);
- start_mem += PAGE_SIZE;
+ if (!pgd_val(*pg_dir)) {
+ memset((void *)start_mem, 0, PAGE_SIZE);
+ pgd_val(*pg_dir) = _PAGE_TABLE | __pa(start_mem);
+ start_mem += PAGE_SIZE;
+ }
}
return start_mem;
@@ -336,6 +332,11 @@
address += PAGE_SIZE;
}
}
+
+ /* define VMALLOC_START */
+ high_memory = (void *) (end_mem & PAGE_MASK);
+ start_mem = kptbl_init(start_mem);
+
start_mem = fixmap_init(start_mem);
#ifdef __SMP__
start_mem = init_smp_mappings(start_mem);
@@ -392,7 +393,6 @@
unsigned long tmp;
end_mem &= PAGE_MASK;
- high_memory = (void *) end_mem;
max_mapnr = num_physpages = MAP_NR(end_mem);
/* clear the zero-page */
--- /usr/tmp/p_rdiff_a00Eew/pgtable.h Wed Feb 17 12:58:37 1999
+++ include/asm-i386/pgtable.h Wed Feb 17 13:35:36 1999
@@ -208,7 +208,9 @@
#define VMALLOC_OFFSET (8*1024*1024)
#define VMALLOC_START (((unsigned long) high_memory + VMALLOC_OFFSET) &
~(VMALLOC_OFFSET-1))
#define VMALLOC_VMADDR(x) ((unsigned long)(x))
-#define VMALLOC_END (FIXADDR_START)
+#define VMALLOC_RESERVE (64 << 20)
+#define VMALLOC_END (((FIXADDR_START - VMALLOC_START) > (VMALLOC_RESERVE))
? \
+ (VMALLOC_START + VMALLOC_RESERVE) :
(FIXADDR_START))
/*
* The 4MB page is guessing.. Detailed in the infamous "Chapter H"
@@ -438,7 +440,6 @@
}
extern pte_t *get_pte_slow(pmd_t *pmd, unsigned long address_preadjusted);
-extern pte_t *get_pte_kernel_slow(pmd_t *pmd, unsigned long
address_preadjusted);
extern __inline__ pte_t *get_pte_fast(void)
{
@@ -479,7 +480,6 @@
}
extern void __bad_pte(pmd_t *pmd);
-extern void __bad_pte_kernel(pmd_t *pmd);
#define pte_free_kernel(pte) free_pte_fast(pte)
#define pte_free(pte) free_pte_fast(pte)
@@ -489,18 +489,6 @@
extern inline pte_t * pte_alloc_kernel(pmd_t * pmd, unsigned long address)
{
address = (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
- if (pmd_none(*pmd)) {
- pte_t * page = (pte_t *) get_pte_fast();
-
- if (!page)
- return get_pte_kernel_slow(pmd, address);
- pmd_val(*pmd) = _KERNPG_TABLE + __pa(page);
- return page + address;
- }
- if (pmd_bad(*pmd)) {
- __bad_pte_kernel(pmd);
- return NULL;
- }
return (pte_t *) pmd_page(*pmd) + address;
}
@@ -545,32 +533,7 @@
extern int do_check_pgt_cache(int, int);
-extern inline void set_pgdir(unsigned long address, pgd_t entry)
-{
- struct task_struct * p;
- pgd_t *pgd;
-#ifdef __SMP__
- int i;
-#endif
-
- read_lock(&tasklist_lock);
- for_each_task(p) {
- if (!p->mm)
- continue;
- *pgd_offset(p->mm,address) = entry;
- }
- read_unlock(&tasklist_lock);
-#ifndef __SMP__
- for (pgd = (pgd_t *)pgd_quicklist; pgd; pgd = (pgd_t *)*(unsigned long
*)pgd)
- pgd[address >> PGDIR_SHIFT] = entry;
-#else
- /* To pgd_alloc/pgd_free, one holds master kernel lock and so does our
callee, so we can
- modify pgd caches of other CPUs as well. -jj */
- for (i = 0; i < NR_CPUS; i++)
- for (pgd = (pgd_t *)cpu_data[i].pgd_quick; pgd; pgd = (pgd_t
*)*(unsigned long *)pgd)
- pgd[address >> PGDIR_SHIFT] = entry;
-#endif
-}
+#define set_pgdir(addr, entry) do { } while (0)
extern pgd_t swapper_pg_dir[1024];
-
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