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Thu, 4 Apr 2024 07:05:50 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap2.dmz-prg2.suse.org with ESMTPSA id yCTjIE5RDmY6cgAAn2gu4w (envelope-from ); Thu, 04 Apr 2024 07:05:50 +0000 From: Oscar Salvador To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Vlastimil Babka , Marco Elver , Andrey Konovalov , Alexander Potapenko , Alexandre Ghiti , Oscar Salvador Subject: [PATCH v4 3/4] mm,page_owner: Fix accounting of pages when migrating Date: Thu, 4 Apr 2024 09:07:01 +0200 Message-ID: <20240404070702.2744-4-osalvador@suse.de> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240404070702.2744-1-osalvador@suse.de> References: <20240404070702.2744-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: p63xxezm5fhq5gjitkynfwbpwyhwygpk X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 714BF4000E X-Rspam-User: X-HE-Tag: 1712214352-676438 X-HE-Meta: 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 /gWlywtU /bPNfqB2u6fIZPcN6+X03zKm6xvxZj5fR80tygyn/I1/DAzsI74ZAZaR+R3LV2CYVBIDdXb448D+UX03vdQC43BOYH3EWBhuELPxLDhSiXAarnxz5viiHQjFoyqKGfdPklhBkYl9Bh9Kknb9zRqu9Mob5TR8fMTpGssrz+PeF0UnEy68uksfc/sptzUkKW/jd6QZfFGC2mSiCfvFUiVmHoO6kPTgwLyh7aW4823yxfvZzpUDYK+lwVgX2Cyb36rmw1RjWutvRbD8BZg9VfPXWUS/GlQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Upon migration, new allocated pages are being given the handle of the old pages. This is problematic because it means that for the stack which allocated the old page, we will be substracting the old page + the new one when that page is freed, creating an accounting imbalance. There is an interest in keeping it that way, as otherwise the output will biased towards migration stacks should those operations occur often, but that is not really helpful. The link from the new page to the old stack is being performed by calling __update_page_owner_handle() in __folio_copy_owner(). The only thing that is left is to link the migrate stack to the old page, so the old page will be subtracted from the migrate stack, avoiding by doing so any possible imbalance. Fixes: 217b2119b9e2 ("mm,page_owner: implement the tracking of the stacks count") Signed-off-by: Oscar Salvador Reviewed-by: Vlastimil Babka --- mm/page_owner.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/mm/page_owner.c b/mm/page_owner.c index 5df0d6892bdc..b4476f45b376 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -366,9 +366,12 @@ void __split_page_owner(struct page *page, int old_order, int new_order) void __folio_copy_owner(struct folio *newfolio, struct folio *old) { + int i; struct page_ext *old_ext; struct page_ext *new_ext; struct page_owner *old_page_owner; + struct page_owner *new_page_owner; + depot_stack_handle_t migrate_handle; old_ext = page_ext_get(&old->page); if (unlikely(!old_ext)) @@ -381,6 +384,8 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old) } old_page_owner = get_page_owner(old_ext); + new_page_owner = get_page_owner(new_ext); + migrate_handle = new_page_owner->handle; __update_page_owner_handle(new_ext, old_page_owner->handle, old_page_owner->order, old_page_owner->gfp_mask, old_page_owner->last_migrate_reason, @@ -395,6 +400,16 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old) old_page_owner->free_pid, old_page_owner->free_tgid, old_page_owner->free_ts_nsec); + /* + * We linked the original stack to the new folio, we need to do the same + * for the new one and the old folio otherwise there will be an imbalance + * when subtracting those pages from the stack. + */ + for (i = 0; i < (1 << new_page_owner->order); i++) { + old_page_owner->handle = migrate_handle; + old_ext = page_ext_next(old_ext); + old_page_owner = get_page_owner(old_ext); + } page_ext_put(new_ext); page_ext_put(old_ext); -- 2.44.0