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, 15 Jan 2015 22:51:30 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by
 removing preemption on/off

On Thu, 15 Jan 2015 21:27:14 -0600 (CST)
Christoph Lameter <cl@...ux.com> wrote:

> 
> The %gs register is not used since the address of the per cpu area is
> available as one of the first fields in the per cpu areas.

Have you disassembled your code?

Looking at put_cpu_partial() from 3.19-rc3 where it does:

		oldpage = this_cpu_read(s->cpu_slab->partial);

I get:

		mov    %gs:0x18(%rax),%rdx

Looks to me that %gs is used.


I haven't done benchmarks in a while, so perhaps accessing the %gs
segment isn't as expensive as I saw it before. I'll have to profile
function tracing on my i7 and see where things are slow again.


-- Steve
--
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/

Powered by blists - more mailing lists