linux-kernel - Re: [PATCH v4 0/5] move per-vma lock into vm_area

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: <hdvig2tptf3hi6nmszafarzqb6j56abfbebppqmruvpihlf435@46b57hyw2pfc>
Date: Wed, 20 Nov 2024 14:10:44 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: akpm@...ux-foundation.org, willy@...radead.org, 
	liam.howlett@...cle.com, lorenzo.stoakes@...cle.com, mhocko@...e.com, vbabka@...e.cz, 
	hannes@...xchg.org, mjguzik@...il.com, oliver.sang@...el.com, 
	mgorman@...hsingularity.net, david@...hat.com, peterx@...hat.com, oleg@...hat.com, 
	dave@...olabs.net, paulmck@...nel.org, brauner@...nel.org, dhowells@...hat.com, 
	hdanton@...a.com, hughd@...gle.com, minchan@...gle.com, jannh@...gle.com, 
	souravpanda@...gle.com, pasha.tatashin@...een.com, corbet@....net, 
	linux-doc@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	kernel-team@...roid.com
Subject: Re: [PATCH v4 0/5] move per-vma lock into vm_area_struct

On Tue, Nov 19, 2024 at 04:08:21PM -0800, Suren Baghdasaryan wrote:
> Back when per-vma locks were introduces, vm_lock was moved out of
> vm_area_struct in [1] because of the performance regression caused by
> false cacheline sharing. Recent investigation [2] revealed that the
> regressions is limited to a rather old Broadwell microarchitecture and
> even there it can be mitigated by disabling adjacent cacheline
> prefetching, see [3].

If 'struct vm_area_struct' is prone to performance issues due to
cacheline misalignments then we should do something about the
__randomize_layout tag for it. I imagine we can identify the fields
which might be performance critical to be on same cacheline or different
cacheline due to false sharing then we can divide the fields into
different cacheline groups and fields can be __randomize_layout within
the group. WDYT?