linux-kernel - Re: [PATCH v2] sched, timer: Use atomics for thread_group

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, 19 Mar 2015 10:59:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jason Low <jason.low2@...com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Scott Norton <scott.norton@...com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] sched, timer: Use atomics for thread_group_cputimer to
 improve scalability

On Thu, Mar 19, 2015 at 10:21 AM, Jason Low <jason.low2@...com> wrote:
>
> I tested this patch on a 32 bit ARM system with 4 cores. Using the
> generic 64 bit atomics, I did not see any performance change with this
> patch, and the relevant functions (account_group_*_time(), ect...) don't
> show up in perf reports.

Ok.

> One factor might be because locking/cacheline contention isn't as
> apparent on smaller systems to begin with, and lib/atomic64.c also
> mentions that "this is expected to used on systems with small numbers of
> CPUs (<= 4 or so)".

Yeah, that's probably a valid argument anyway - 32-bit systems aren't
really going to be multi-node big systems any more.

So I'm ok with the patch,

                      Linus
--
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/