mm/damon/vaddr: remove comparison between mm and last_mm when checking region accesses

The damon regions that belong to the same damon target have the same
'struct mm_struct *mm', so it's unnecessary to compare the mm and last_mm
objects among the damon regions in one damon target when checking
accesses.  But the check is necessary when the target changed in
'__damon_va_check_accesses()', so we can simplify the whole operation by
using the bool 'same_target' to indicate whether the target changed.

Link: https://lkml.kernel.org/r/1661590971-20893-3-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 34a72f5e13f5fd313bd0d95613f4bf4285f5de9a..a8505ad47c60930eb0d2e130696ebfdd3033ed5a 100644 (file)
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -543,15 +543,14 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
  * r   the region to be checked
  */
 static void __damon_va_check_access(struct mm_struct *mm,
-                               struct damon_region *r)
+                               struct damon_region *r, bool same_target)
 {
-       static struct mm_struct *last_mm;
        static unsigned long last_addr;
        static unsigned long last_page_sz = PAGE_SIZE;
        static bool last_accessed;
 
        /* If the region is in the last checked page, reuse the result */
-       if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
+       if (same_target && (ALIGN_DOWN(last_addr, last_page_sz) ==
                                ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
                if (last_accessed)
                        r->nr_accesses++;
@@ -562,7 +561,6 @@ static void __damon_va_check_access(struct mm_struct *mm,
        if (last_accessed)
                r->nr_accesses++;
 
-       last_mm = mm;
        last_addr = r->sampling_addr;
 }
 
@@ -572,14 +570,17 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
        struct mm_struct *mm;
        struct damon_region *r;
        unsigned int max_nr_accesses = 0;
+       bool same_target;
 
        damon_for_each_target(t, ctx) {
                mm = damon_get_mm(t);
                if (!mm)
                        continue;
+               same_target = false;
                damon_for_each_region(r, t) {
-                       __damon_va_check_access(mm, r);
+                       __damon_va_check_access(mm, r, same_target);
                        max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
+                       same_target = true;
                }
                mmput(mm);
        }