2023-10-27 13:23:21

by Brendan Jackman

Subject: [PATCH] mm/page_alloc: Dedupe some memcg uncharging logic

The duplication makes it seem like some work is required before
uncharging in the !PageHWPoison case. But it isn't, so we can simplify
the code a little.

Note the PageMemcgKmem check is redundant, but I've left it in as it
avoids an unnecessary function call.

Signed-Off-By: Brendan Jackman <[email protected]>
Change-Id: Ibe0f9941b6b24fc98ea2510a75d0a0d1066a2a2e
---
mm/page_alloc.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 85741403948f..b9e81e416e73 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1084,13 +1084,11 @@ static __always_inline bool free_pages_prepare(struct page *page,
trace_mm_page_free(page, order);
kmsan_free_page(page, order);

+ if (memcg_kmem_online() && PageMemcgKmem(page))
+ __memcg_kmem_uncharge_page(page, order);
+
if (unlikely(PageHWPoison(page)) && !order) {
- /*
- * Do not let hwpoison pages hit pcplists/buddy
- * Untie memcg state and reset page's owner
- */
- if (memcg_kmem_online() && PageMemcgKmem(page))
- __memcg_kmem_uncharge_page(page, order);
+ /* Do not let hwpoison pages hit pcplists/buddy */
reset_page_owner(page, order);
page_table_check_free(page, order);
return false;
@@ -1122,8 +1120,6 @@ static __always_inline bool free_pages_prepare(struct page *page,
}
if (PageMappingFlags(page))
page->mapping = NULL;
- if (memcg_kmem_online() && PageMemcgKmem(page))
- __memcg_kmem_uncharge_page(page, order);
if (is_check_pages_enabled()) {
if (free_page_is_bad(page))
bad++;
--
2.42.0.820.g83a721a137-goog

2023-10-31 09:56:25

by Brendan Jackman

Subject: Re: [PATCH] mm/page_alloc: Dedupe some memcg uncharging logic

On Fri, 27 Oct 2023 at 15:22, Brendan Jackman <[email protected]> wrote:

> Signed-Off-By: Brendan Jackman <[email protected]>
> Change-Id: Ibe0f9941b6b24fc98ea2510a75d0a0d1066a2a2e

Agh, sorry, it just jumped into my head that I neglected to run
checkpatch and of course the commit message is garbage. I will leave
this a few days in case there are other comments before I send a v2.

FWIW I did at least run the mm kselftests via QEMU, results are the
same with and without the patch.