The patch titled
Subject: filemap: batch PTE mappings
has been added to the -mm mm-unstable branch. Its filename is
filemap-batch-pte-mappings.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/filemap-batch-pte-mappings.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Subject: filemap: batch PTE mappings
Date: Mon, 10 Jul 2023 21:43:38 +0100
Call set_pte_range() once per contiguous range of the folio instead of
once per page. This batches the updates to mm counters and the rmap.
With a will-it-scale.page_fault3 like app (change file write fault testing
to read fault testing. Trying to upstream it to will-it-scale at [1]) got
15% performance gain on a 48C/96T Cascade Lake test box with 96 processes
running against xfs.
Perf data collected before/after the change:
18.73%--page_add_file_rmap
|
--11.60%--__mod_lruvec_page_state
|
|--7.40%--__mod_memcg_lruvec_state
| |
| --5.58%--cgroup_rstat_updated
|
--2.53%--__mod_lruvec_state
|
--1.48%--__mod_node_page_state
9.93%--page_add_file_rmap_range
|
--2.67%--__mod_lruvec_page_state
|
|--1.95%--__mod_memcg_lruvec_state
| |
| --1.57%--cgroup_rstat_updated
|
--0.61%--__mod_lruvec_state
|
--0.54%--__mod_node_page_state
The running time of __mode_lruvec_page_state() is reduced about 9%.
[1]: https://github.com/antonblanchard/will-it-scale/pull/37
Link: https://lkml.kernel.org/r/20230710204339.3554919-38-willy@xxxxxxxxxxxxx
Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 43 +++++++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 14 deletions(-)
--- a/mm/filemap.c~filemap-batch-pte-mappings
+++ a/mm/filemap.c
@@ -3480,11 +3480,12 @@ static vm_fault_t filemap_map_folio_rang
struct file *file = vma->vm_file;
struct page *page = folio_page(folio, start);
unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
- unsigned int ref_count = 0, count = 0;
+ unsigned int count = 0;
+ pte_t *old_ptep = vmf->pte;
do {
- if (PageHWPoison(page))
- continue;
+ if (PageHWPoison(page + count))
+ goto skip;
if (mmap_miss > 0)
mmap_miss--;
@@ -3494,20 +3495,34 @@ static vm_fault_t filemap_map_folio_rang
* handled in the specific fault path, and it'll prohibit the
* fault-around logic.
*/
- if (!pte_none(*vmf->pte))
- continue;
+ if (!pte_none(vmf->pte[count]))
+ goto skip;
- if (vmf->address == addr)
+ count++;
+ continue;
+skip:
+ if (count) {
+ set_pte_range(vmf, folio, page, count, addr);
+ folio_ref_add(folio, count);
+ if (in_range(vmf->address, addr, count))
+ ret = VM_FAULT_NOPAGE;
+ }
+
+ count++;
+ page += count;
+ vmf->pte += count;
+ addr += count * PAGE_SIZE;
+ count = 0;
+ } while (--nr_pages > 0);
+
+ if (count) {
+ set_pte_range(vmf, folio, page, count, addr);
+ folio_ref_add(folio, count);
+ if (in_range(vmf->address, addr, count))
ret = VM_FAULT_NOPAGE;
+ }
- ref_count++;
- set_pte_range(vmf, folio, page, 1, addr);
- } while (vmf->pte++, page++, addr += PAGE_SIZE, ++count < nr_pages);
-
- /* Restore the vmf->pte */
- vmf->pte -= nr_pages;
-
- folio_ref_add(folio, ref_count);
+ vmf->pte = old_ptep;
WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
return ret;
_
Patches currently in -mm which might be from fengwei.yin@xxxxxxxxx are
filemap-add-filemap_map_folio_range.patch
rmap-add-folio_add_file_rmap_range.patch
mm-convert-do_set_pte-to-set_pte_range.patch
filemap-batch-pte-mappings.patch
