netdev - Re: [RFC PATCH] slub: RFC: Improving SLUB performance with 38% on NO-PREEMPT

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: <1433471877.1895.51.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 04 Jun 2015 19:37:57 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Alexander Duyck <alexander.duyck@...il.com>,
	linux-mm@...ck.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] slub: RFC: Improving SLUB performance with 38% on
 NO-PREEMPT

On Thu, 2015-06-04 at 12:31 +0200, Jesper Dangaard Brouer wrote:
> This patch improves performance of SLUB allocator fastpath with 38% by
> avoiding the call to this_cpu_cmpxchg_double() for NO-PREEMPT kernels.
> 
> Reviewers please point out why this change is wrong, as such a large
> improvement should not be possible ;-)

I am not sure if anyone already answered, but the cmpxchg_double()
is needed to avoid the ABA problem.

This is the whole point using tid _and_ freelist

Preemption is not the only thing that could happen here, think of
interrupts.



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html