linux-kernel - Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM

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:	Fri, 10 Dec 2010 11:08:24 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Mikael Pettersson <mikpe@...uu.se>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	John Stultz <johnstul@...ibm.com>
Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM

On Thu, 2010-12-09 at 15:35 -0800, Venkatesh Pallipadi wrote:
> 
> Just to make sure, update_rq_clock() always gets called on current
> CPU. Right? 

No, specifically not. If that were the case we wouldn't need the
cross-cpu synced timestamp. Things like load-balancing and
remote-wakeups need to update a remote CPUs clock.

> The pending patches I have optimizes
> account_system_vtime() to use this_cpu_write and friends. Want to make
> sure this change will still keep that optimization relevant.

Ah, good point, remote CPUs updating that will mess with the consistency
of the per-cpu timestamps due to non atomic updates :/

Bugger.. making them atomics will make it even more expensive. /me goes
ponder.
--
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/