linux-kernel - Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user

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]

Date:	Thu, 03 May 2012 16:26:48 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	rajman mekaco <rajman.mekaco@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Lameter <cl@...two.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into
 per user_struct spinlock

On 05/03/2012 03:31 PM, Peter Zijlstra wrote:
> On Thu, 2012-05-03 at 23:04 +0530, rajman mekaco wrote:
>> The user_shm_lock and user_shm_unlock functions use a single global
>> spinlock for protecting the user->locked_shm.
>
> Are you very sure its only protecting user state? This changelog doesn't
> convince me you've gone through everything and found it good.
>
>> This is an overhead for multiple CPUs calling this code even if they
>> are having different user_struct.
>>
>> Remove the global shmlock_user_lock and introduce and use a new
>> spinlock inside of the user_struct structure.
>
> While I don't immediately see anything wrong with it, I doubt its
> useful. What workload run with enough users that this makes a difference
> one way or another?

When running with containers and/or LXC, I believe that
each UID in each container gets its own user_struct, but
you do raise a good question - what user programs call
mlock anyway, and how often?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/