The patch titled
Subject: fs/proc/task_mmu: Add fast paths to get/clear PAGE_IS_WRITTEN flag
has been added to the -mm mm-unstable branch. Its filename is
fs-proc-task_mmu-add-fast-paths-to-get-clear-page_is_written-flag.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-proc-task_mmu-add-fast-paths-to-get-clear-page_is_written-flag.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: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Subject: fs/proc/task_mmu: Add fast paths to get/clear PAGE_IS_WRITTEN flag
Date: Mon, 21 Aug 2023 19:15:15 +0500
Adding fast code paths to handle specifically only get and/or clear
operation of PAGE_IS_WRITTEN, increases its performance by 0-35%. The
results of some test cases are given below:
Test-case-1
t1 = (Get + WP) time
t2 = WP time
t1 t2
Without this patch: 140-170mcs 90-115mcs
With this patch: 110mcs 80mcs
Worst case diff: 35% faster 30% faster
Test-case-2
t3 = atomic Get and WP
t3
Without this patch: 120-140mcs
With this patch: 100-110mcs
Worst case diff: 21% faster
Link: https://lkml.kernel.org/r/20230821141518.870589-4-usama.anjum@xxxxxxxxxxxxx
Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Cc: Alex Sierra <alex.sierra@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Cc: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Miroslaw <emmir@xxxxxxxxxx>
Cc: MichaÅ? MirosÅ?aw <mirq-linux@xxxxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Paul Gofman <pgofman@xxxxxxxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-add-fast-paths-to-get-clear-page_is_written-flag
+++ a/fs/proc/task_mmu.c
@@ -2145,6 +2145,41 @@ static int pagemap_scan_pmd_entry(pmd_t
return 0;
}
+ if (!p->vec_out) {
+ /* Fast path for performing exclusive WP */
+ for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
+ if (pte_uffd_wp(ptep_get(pte)))
+ continue;
+ make_uffd_wp_pte(vma, addr, pte);
+ if (!flush_end)
+ start = addr;
+ flush_end = addr + PAGE_SIZE;
+ }
+ goto flush_and_return;
+ }
+
+ if (!p->arg.category_anyof_mask && !p->arg.category_inverted &&
+ p->arg.category_mask == PAGE_IS_WRITTEN &&
+ p->arg.return_mask == PAGE_IS_WRITTEN) {
+ for (addr = start; addr < end; pte++, addr += PAGE_SIZE) {
+ unsigned long next = addr + PAGE_SIZE;
+
+ if (pte_uffd_wp(ptep_get(pte)))
+ continue;
+ ret = pagemap_scan_output(p->cur_vma_category | PAGE_IS_WRITTEN,
+ p, addr, &next);
+ if (next == addr)
+ break;
+ if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+ continue;
+ make_uffd_wp_pte(vma, addr, pte);
+ if (!flush_end)
+ start = addr;
+ flush_end = next;
+ }
+ goto flush_and_return;
+ }
+
for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
unsigned long categories = p->cur_vma_category |
pagemap_page_category(p, vma, addr, ptep_get(pte));
@@ -2168,6 +2203,7 @@ static int pagemap_scan_pmd_entry(pmd_t
flush_end = next;
}
+flush_and_return:
if (flush_end)
flush_tlb_range(vma, start, addr);
_
Patches currently in -mm which might be from usama.anjum@xxxxxxxxxxxxx are
fs-proc-task_mmu-implement-ioctl-to-get-and-optionally-clear-info-about-ptes.patch
fs-proc-task_mmu-add-fast-paths-to-get-clear-page_is_written-flag.patch
tools-headers-uapi-update-linux-fsh-with-the-kernel-sources.patch
mm-pagemap-add-documentation-of-pagemap_scan-ioctl.patch
selftests-mm-add-pagemap-ioctl-tests.patch
