linux-kernel - Re: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA maple tree in reverse order

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: <llxw4jc4okxjxjcco5vacqiushvr642u2lto5sml3vc6wlqboe@lyfqb5anihq6>
Date: Thu, 4 Sep 2025 16:50:20 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: zhongjinji <zhongjinji@...or.com>
Cc: mhocko@...e.com, rientjes@...gle.com, akpm@...ux-foundation.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, tglx@...utronix.de, 
	liam.howlett@...cle.com, lorenzo.stoakes@...cle.com, surenb@...gle.com, 
	liulu.liu@...or.com, feng.han@...or.com
Subject: Re: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA
 maple tree in reverse order

On Wed, Sep 03, 2025 at 05:27:29PM +0800, zhongjinji wrote:
> Although the oom_reaper is delayed and it gives the oom victim chance to
> clean up its address space this might take a while especially for
> processes with a large address space footprint. In those cases
> oom_reaper might start racing with the dying task and compete for shared
> resources - e.g. page table lock contention has been observed.
> 
> Reduce those races by reaping the oom victim from the other end of the
> address space.
> 
> It is also a significant improvement for process_mrelease(). When a process
> is killed, process_mrelease is used to reap the killed process and often
> runs concurrently with the dying task. The test data shows that after
> applying the patch, lock contention is greatly reduced during the procedure
> of reaping the killed process.
> 
> Without the patch:
> |--99.74%-- oom_reaper
> |  |--76.67%-- unmap_page_range
> |  |  |--33.70%-- __pte_offset_map_lock
> |  |  |  |--98.46%-- _raw_spin_lock
> |  |  |--27.61%-- free_swap_and_cache_nr
> |  |  |--16.40%-- folio_remove_rmap_ptes
> |  |  |--12.25%-- tlb_flush_mmu
> |  |--12.61%-- tlb_finish_mmu
> 
> With the patch:
> |--98.84%-- oom_reaper
> |  |--53.45%-- unmap_page_range
> |  |  |--24.29%-- [hit in function]
> |  |  |--48.06%-- folio_remove_rmap_ptes
> |  |  |--17.99%-- tlb_flush_mmu
> |  |  |--1.72%-- __pte_offset_map_lock
> |  |--30.43%-- tlb_finish_mmu
> 
> Signed-off-by: zhongjinji <zhongjinji@...or.com>

Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>