linux-kernel - Re: [PATCH 34/35] x86: use num

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, 18 Feb 2010 11:53:31 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH 34/35] x86: use num_processors for possible cpus

On 02/18/2010 11:48 AM, Christoph Lameter wrote:
>>
>> Yes, and I have repeatedly requested that we allocate the memory on the
>> first up of a disabled CPU rather than eagerly, but in *most*
>> configurations the amount is relatively small.
> 
> The size of the static per cpu segment is likely around 30k and you will
> likely add another 30k in dynamic allocations.
> 
> As I have also repeatedly stated: Dynamic percpu data allocation when
> onlining / offlining processors will complicate locking (cannot rely on
> percpu be present anymore) and introduce numerous additional
> hotplug notifiers into subsystems.

I did state explicitly "on first up".  Trying to free it would be
insane.  There are a couple of subsystems which are percpu memory
pigs... so far it's not clear any of them actually matters in a
production kernel.  60K * 16 phantom processors is still ~ 1 MB, which
probably isn't enough to worry about but isn't great.

	-hpa
--
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/