linux-kernel - Re: [PATCH v3 1/3] mm/numa: no task_numa

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2cdc6d9a-0855-4209-9745-0ae15c4498a8@redhat.com>
Date: Fri, 9 Aug 2024 17:29:20 +0200
From: David Hildenbrand <david@...hat.com>
To: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 "Huang, Ying" <ying.huang@...el.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Yang Shi <shy828301@...il.com>,
 Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v3 1/3] mm/numa: no task_numa_fault() call if PTE is
 changed

On 09.08.24 16:59, Zi Yan wrote:
> When handling a numa page fault, task_numa_fault() should be called by a
> process that restores the page table of the faulted folio to avoid
> duplicated stats counting. Commit b99a342d4f11 ("NUMA balancing: reduce
> TLB flush via delaying mapping on hint page fault") restructured
> do_numa_page() and did not avoid task_numa_fault() call in the second page
> table check after a numa migration failure. Fix it by making all
> !pte_same() return immediately.
> 
> This issue can cause task_numa_fault() being called more than necessary
> and lead to unexpected numa balancing results (It is hard to tell whether
> the issue will cause positive or negative performance impact due to
> duplicated numa fault counting).
> 
> Reported-by: "Huang, Ying" <ying.huang@...el.com>
> Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/
> Fixes: b99a342d4f11 ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Zi Yan <ziy@...dia.com>
> ---

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb