[PATCH v4] mm/filemap: change ->index to PAGE_SIZE for hugetlb pages
From: Sidhartha Kumar
Date: Mon Aug 14 2023 - 17:52:42 EST
This patchset attempts to implement a listed filemap TODO which is
changing hugetlb folios to have ->index in PAGE_SIZE. This simplifies many
functions within filemap.c as they have to special case hugetlb pages.
New wrappers for hugetlb code are used to interact with the page cache
using a linear index.
========================= PERFORMANCE ======================================
Perf was used to check the performance differences after the patch. Overall
the performance is similar to mainline with a very small larger overhead that
occurs in __filemap_add_folio() and hugetlb_add_to_page_cache(). This is because
of the larger overhead that occurs in xa_load() and xa_store() as the
xarray is now using more entries to store hugetlb folios in the page cache.
Timing
aarch64
2MB Page Size
6.5-rc3 + this patch:
[root@sidhakum-ol9-1 hugepages]# time fallocate -l 700GB test.txt
real 1m49.568s
user 0m0.000s
sys 1m49.461s
6.5-rc3:
[root]# time fallocate -l 700GB test.txt
real 1m47.495s
user 0m0.000s
sys 1m47.370s
1GB Page Size
6.5-rc3 + this patch:
[root@sidhakum-ol9-1 hugepages1G]# time fallocate -l 700GB test.txt
real 1m47.024s
user 0m0.000s
sys 1m46.921s
6.5-rc3:
[root@sidhakum-ol9-1 hugepages1G]# time fallocate -l 700GB test.txt
real 1m44.551s
user 0m0.000s
sys 1m44.438s
x86
2MB Page Size
6.5-rc3 + this patch:
[root@sidhakum-ol9-2 hugepages]# time fallocate -l 100GB test.txt
real 0m22.383s
user 0m0.000s
sys 0m22.255s
6.5-rc3:
[opc@sidhakum-ol9-2 hugepages]$ time sudo fallocate -l 100GB /dev/hugepages/test.txt
real 0m22.735s
user 0m0.038s
sys 0m22.567s
1GB Page Size
6.5-rc3 + this patch:
[root@sidhakum-ol9-2 hugepages1GB]# time fallocate -l 100GB test.txt
real 0m25.786s
user 0m0.001s
sys 0m25.589s
6.5-rc3:
[root@sidhakum-ol9-2 hugepages1G]# time fallocate -l 100GB test.txt
real 0m33.454s
user 0m0.001s
sys 0m33.193s
aarch64:
workload - fallocate a 700GB file backed by huge pages
6.5-rc3 + this patch:
2MB Page Size:
--100.00%--__arm64_sys_fallocate
ksys_fallocate
vfs_fallocate
hugetlbfs_fallocate
|
|--95.04%--__pi_clear_page
|
|--3.57%--clear_huge_page
| |
| |--2.63%--rcu_all_qs
| |
| --0.91%--__cond_resched
|
--0.67%--__cond_resched
0.17% 0.00% 0 fallocate [kernel.vmlinux] [k] hugetlb_add_to_page_cache
0.14% 0.10% 11 fallocate [kernel.vmlinux] [k] __filemap_add_folio
6.5-rc3
2MB Page Size:
--100.00%--__arm64_sys_fallocate
ksys_fallocate
vfs_fallocate
hugetlbfs_fallocate
|
|--94.91%--__pi_clear_page
|
|--4.11%--clear_huge_page
| |
| |--3.00%--rcu_all_qs
| |
| --1.10%--__cond_resched
|
--0.59%--__cond_resched
0.08% 0.01% 1 fallocate [kernel.kallsyms] [k] hugetlb_add_to_page_cache
0.05% 0.03% 3 fallocate [kernel.kallsyms] [k] __filemap_add_folio
x86
workload - fallocate a 100GB file backed by huge pages
6.5-rc3 + this patch:
2MB Page Size:
hugetlbfs_fallocate
|
--99.57%--clear_huge_page
|
--98.47%--clear_page_erms
|
--0.53%--asm_sysvec_apic_timer_interrupt
0.04% 0.04% 1 fallocate [kernel.kallsyms] [k] xa_load
0.04% 0.00% 0 fallocate [kernel.kallsyms] [k] hugetlb_add_to_page_cache
0.04% 0.00% 0 fallocate [kernel.kallsyms] [k] __filemap_add_folio
0.04% 0.00% 0 fallocate [kernel.kallsyms] [k] xas_store
6.5-rc3
2MB Page Size:
--99.93%--__x64_sys_fallocate
vfs_fallocate
hugetlbfs_fallocate
|
--99.38%--clear_huge_page
|
|--98.40%--clear_page_erms
|
--0.59%--__cond_resched
0.03% 0.03% 1 fallocate [kernel.kallsyms] [k] __filemap_add_folio
========================= TESTING ======================================
This patch passes libhugetlbfs tests and LTP hugetlb tests
********** TEST SUMMARY
* 2M
* 32-bit 64-bit
* Total testcases: 110 113
* Skipped: 0 0
* PASS: 107 113
* FAIL: 0 0
* Killed by signal: 3 0
* Bad configuration: 0 0
* Expected FAIL: 0 0
* Unexpected PASS: 0 0
* Test not present: 0 0
* Strange test result: 0 0
**********
###############################################################
Done executing testcases.
LTP Version: 20220527-178-g2761a81c4
###############################################################
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
---
rebased on mm-unstable 08/14/23
RFC v2[1] -> v1[2]
-change direction of series to maintain both huge and base page size index
rather than try to get rid of all references to a huge page sized index.
v1 -> v2[3]
- squash seperate filemap and hugetlb changes into one patch to allow
for bisection per Matthew
- get rid of page_to_index()
- fix errors in hugetlb_fallocate() and remove_inode_hugepages()
v2 -> v3[4]
- gather performance data per Mike Kravetz
- remove start variable in remove_inode_hugepages() per Mike Kravetz
- remove hugetlb special case within folio_file_page()
v3 -> v4
- rebase to current mm-unstable
- include time data per Mike Kravetz
[1]: https://lore.kernel.org/linux-mm/20230519220142.212051-1-sidhartha.kumar@xxxxxxxxxx/T/
[2]: https://lore.kernel.org/lkml/20230609194947.37196-1-sidhartha.kumar@xxxxxxxxxx/
[3]: https://lore.kernel.org/lkml/ZLtVlJA+V2+2yjxc@xxxxxxxxxxxxxxxxxxxx/T/
[4]: https://lore.kernel.org/lkml/20230811233939.GA105247@monkey/T/
fs/hugetlbfs/inode.c | 15 ++++++++-------
include/linux/hugetlb.h | 12 ++++++++++++
include/linux/pagemap.h | 29 ++---------------------------
mm/filemap.c | 34 ++++++++++------------------------
mm/hugetlb.c | 11 ++++++-----
5 files changed, 38 insertions(+), 63 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index e7611ae1e6120..ec0f856a1228c 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -661,21 +661,20 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
{
struct hstate *h = hstate_inode(inode);
struct address_space *mapping = &inode->i_data;
- const pgoff_t start = lstart >> huge_page_shift(h);
- const pgoff_t end = lend >> huge_page_shift(h);
+ const pgoff_t end = lend >> PAGE_SHIFT;
struct folio_batch fbatch;
pgoff_t next, index;
int i, freed = 0;
bool truncate_op = (lend == LLONG_MAX);
folio_batch_init(&fbatch);
- next = start;
+ next = lstart >> PAGE_SHIFT;
while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
for (i = 0; i < folio_batch_count(&fbatch); ++i) {
struct folio *folio = fbatch.folios[i];
u32 hash = 0;
- index = folio->index;
+ index = folio->index >> huge_page_order(h);
hash = hugetlb_fault_mutex_hash(mapping, index);
mutex_lock(&hugetlb_fault_mutex_table[hash]);
@@ -693,7 +692,9 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
}
if (truncate_op)
- (void)hugetlb_unreserve_pages(inode, start, LONG_MAX, freed);
+ (void)hugetlb_unreserve_pages(inode,
+ lstart >> huge_page_shift(h),
+ LONG_MAX, freed);
}
static void hugetlbfs_evict_inode(struct inode *inode)
@@ -741,7 +742,7 @@ static void hugetlbfs_zero_partial_page(struct hstate *h,
pgoff_t idx = start >> huge_page_shift(h);
struct folio *folio;
- folio = filemap_lock_folio(mapping, idx);
+ folio = filemap_lock_hugetlb_folio(h, mapping, idx);
if (IS_ERR(folio))
return;
@@ -886,7 +887,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
/* See if already present in mapping to avoid alloc/free */
- folio = filemap_get_folio(mapping, index);
+ folio = filemap_get_folio(mapping, index << huge_page_order(h));
if (!IS_ERR(folio)) {
folio_put(folio);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0a393bc02f25b..1bb3fcacdcddf 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -811,6 +811,12 @@ static inline unsigned int blocks_per_huge_page(struct hstate *h)
return huge_page_size(h) / 512;
}
+static inline struct folio *filemap_lock_hugetlb_folio(struct hstate *h,
+ struct address_space *mapping, pgoff_t idx)
+{
+ return filemap_lock_folio(mapping, idx << huge_page_order(h));
+}
+
#include <asm/hugetlb.h>
#ifndef is_hugepage_only_range
@@ -1005,6 +1011,12 @@ static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio
return NULL;
}
+static inline struct folio *filemap_lock_hugetlb_folio(struct hstate *h,
+ struct address_space *mapping, pgoff_t idx)
+{
+ return NULL;
+}
+
static inline int isolate_or_dissolve_huge_page(struct page *page,
struct list_head *list)
{
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 71dd79b4ae0ad..6816d3ccbd7e2 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -729,9 +729,6 @@ static inline pgoff_t folio_next_index(struct folio *folio)
*/
static inline struct page *folio_file_page(struct folio *folio, pgoff_t index)
{
- /* HugeTLBfs indexes the page cache in units of hpage_size */
- if (folio_test_hugetlb(folio))
- return &folio->page;
return folio_page(folio, index & (folio_nr_pages(folio) - 1));
}
@@ -747,9 +744,6 @@ static inline struct page *folio_file_page(struct folio *folio, pgoff_t index)
*/
static inline bool folio_contains(struct folio *folio, pgoff_t index)
{
- /* HugeTLBfs indexes the page cache in units of hpage_size */
- if (folio_test_hugetlb(folio))
- return folio->index == index;
return index - folio_index(folio) < folio_nr_pages(folio);
}
@@ -807,10 +801,9 @@ static inline struct folio *read_mapping_folio(struct address_space *mapping,
}
/*
- * Get index of the page within radix-tree (but not for hugetlb pages).
- * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
+ * Get the offset in PAGE_SIZE (even for hugetlb pages).
*/
-static inline pgoff_t page_to_index(struct page *page)
+static inline pgoff_t page_to_pgoff(struct page *page)
{
struct page *head;
@@ -825,19 +818,6 @@ static inline pgoff_t page_to_index(struct page *page)
return head->index + page - head;
}
-extern pgoff_t hugetlb_basepage_index(struct page *page);
-
-/*
- * Get the offset in PAGE_SIZE (even for hugetlb pages).
- * (TODO: hugetlb pages should have ->index in PAGE_SIZE)
- */
-static inline pgoff_t page_to_pgoff(struct page *page)
-{
- if (unlikely(PageHuge(page)))
- return hugetlb_basepage_index(page);
- return page_to_index(page);
-}
-
/*
* Return byte-offset into filesystem object for page.
*/
@@ -874,12 +854,9 @@ static inline loff_t folio_file_pos(struct folio *folio)
/*
* Get the offset in PAGE_SIZE (even for hugetlb folios).
- * (TODO: hugetlb folios should have ->index in PAGE_SIZE)
*/
static inline pgoff_t folio_pgoff(struct folio *folio)
{
- if (unlikely(folio_test_hugetlb(folio)))
- return hugetlb_basepage_index(&folio->page);
return folio->index;
}
@@ -890,8 +867,6 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
unsigned long address)
{
pgoff_t pgoff;
- if (unlikely(is_vm_hugetlb_page(vma)))
- return linear_hugepage_index(vma, address);
pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
pgoff += vma->vm_pgoff;
return pgoff;
diff --git a/mm/filemap.c b/mm/filemap.c
index 014b73eb96a1d..94e8d96159bc2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -134,11 +134,8 @@ static void page_cache_delete(struct address_space *mapping,
mapping_set_update(&xas, mapping);
- /* hugetlb pages are represented by a single entry in the xarray */
- if (!folio_test_hugetlb(folio)) {
- xas_set_order(&xas, folio->index, folio_order(folio));
- nr = folio_nr_pages(folio);
- }
+ xas_set_order(&xas, folio->index, folio_order(folio));
+ nr = folio_nr_pages(folio);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
@@ -237,7 +234,7 @@ void filemap_free_folio(struct address_space *mapping, struct folio *folio)
if (free_folio)
free_folio(folio);
- if (folio_test_large(folio) && !folio_test_hugetlb(folio))
+ if (folio_test_large(folio))
refs = folio_nr_pages(folio);
folio_put_refs(folio, refs);
}
@@ -858,14 +855,15 @@ noinline int __filemap_add_folio(struct address_space *mapping,
if (!huge) {
int error = mem_cgroup_charge(folio, NULL, gfp);
- VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
if (error)
return error;
charged = true;
- xas_set_order(&xas, index, folio_order(folio));
- nr = folio_nr_pages(folio);
}
+ VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
+ xas_set_order(&xas, index, folio_order(folio));
+ nr = folio_nr_pages(folio);
+
gfp &= GFP_RECLAIM_MASK;
folio_ref_add(folio, nr);
folio->mapping = mapping;
@@ -2038,7 +2036,7 @@ unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
int idx = folio_batch_count(fbatch) - 1;
folio = fbatch->folios[idx];
- if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
+ if (!xa_is_value(folio))
nr = folio_nr_pages(folio);
*start = indices[idx] + nr;
}
@@ -2102,7 +2100,7 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
int idx = folio_batch_count(fbatch) - 1;
folio = fbatch->folios[idx];
- if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
+ if (!xa_is_value(folio))
nr = folio_nr_pages(folio);
*start = indices[idx] + nr;
}
@@ -2143,9 +2141,6 @@ unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
continue;
if (!folio_batch_add(fbatch, folio)) {
unsigned long nr = folio_nr_pages(folio);
-
- if (folio_test_hugetlb(folio))
- nr = 1;
*start = folio->index + nr;
goto out;
}
@@ -2211,9 +2206,6 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
if (!folio_batch_add(fbatch, folio)) {
nr = folio_nr_pages(folio);
-
- if (folio_test_hugetlb(folio))
- nr = 1;
*start = folio->index + nr;
goto out;
}
@@ -2230,10 +2222,7 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
if (nr) {
folio = fbatch->folios[nr - 1];
- if (folio_test_hugetlb(folio))
- *start = folio->index + 1;
- else
- *start = folio_next_index(folio);
+ *start = folio->index + folio_nr_pages(folio);
}
out:
rcu_read_unlock();
@@ -2271,9 +2260,6 @@ unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
continue;
if (!folio_batch_add(fbatch, folio)) {
unsigned long nr = folio_nr_pages(folio);
-
- if (folio_test_hugetlb(folio))
- nr = 1;
*start = folio->index + nr;
goto out;
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5f498e8025cc5..3520c83c56f6f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -952,7 +952,7 @@ static long region_count(struct resv_map *resv, long f, long t)
/*
* Convert the address within this vma to the page offset within
- * the mapping, in pagecache page units; huge pages here.
+ * the mapping, huge page units here.
*/
static pgoff_t vma_hugecache_offset(struct hstate *h,
struct vm_area_struct *vma, unsigned long address)
@@ -5750,7 +5750,7 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
struct vm_area_struct *vma, unsigned long address)
{
struct address_space *mapping = vma->vm_file->f_mapping;
- pgoff_t idx = vma_hugecache_offset(h, vma, address);
+ pgoff_t idx = linear_page_index(vma, address);
struct folio *folio;
folio = filemap_get_folio(mapping, idx);
@@ -5767,6 +5767,7 @@ int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping
struct hstate *h = hstate_inode(inode);
int err;
+ idx <<= huge_page_order(h);
__folio_set_locked(folio);
err = __filemap_add_folio(mapping, folio, idx, GFP_KERNEL, NULL);
@@ -5874,7 +5875,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
* before we get page_table_lock.
*/
new_folio = false;
- folio = filemap_lock_folio(mapping, idx);
+ folio = filemap_lock_hugetlb_folio(h, mapping, idx);
if (IS_ERR(folio)) {
size = i_size_read(mapping->host) >> huge_page_shift(h);
if (idx >= size)
@@ -6183,7 +6184,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
/* Just decrements count, does not deallocate */
vma_end_reservation(h, vma, haddr);
- pagecache_folio = filemap_lock_folio(mapping, idx);
+ pagecache_folio = filemap_lock_hugetlb_folio(h, mapping, idx);
if (IS_ERR(pagecache_folio))
pagecache_folio = NULL;
}
@@ -6315,7 +6316,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
if (is_continue) {
ret = -EFAULT;
- folio = filemap_lock_folio(mapping, idx);
+ folio = filemap_lock_hugetlb_folio(h, mapping, idx);
if (IS_ERR(folio))
goto out;
folio_in_pagecache = true;
--
2.41.0