linux-kernel - Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression

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: <20150906234708.GP26895@dastard>
Date:	Mon, 7 Sep 2015 09:47:09 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Waiman Long <Waiman.Long@...com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [4.2, Regression] Queued spinlocks cause major XFS performance
 regression

On Fri, Sep 04, 2015 at 01:32:33PM +0200, Peter Zijlstra wrote:
> On Fri, Sep 04, 2015 at 06:12:34PM +1000, Dave Chinner wrote:
> > You probably don't even need a VM to reproduce it - that would
> > certainly be an interesting counterpoint if it didn't....
> 
> Even though you managed to restore your DEBUG_SPINLOCK performance by
> changing virt_queued_spin_lock() to use __delay(1), I ran the thing on
> actual hardware just to test.
> 
> [ Note: In any case, I would recommend you use (or at least try)
>   PARAVIRT_SPINLOCKS if you use VMs, as that is where we were looking for
>   performance, the test-and-set fallback really wasn't meant as a
>   performance option (although it clearly sucks worse than expected).

FSUse%        Count         Size    Files/sec     App Overhead
     0      1600000            0     319431.5         10116018
     0      3200000            0     307824.5         10054299
     0      4800000            0     296971.5         10770197
     0      6400000            0     281653.6         11748423
....

PARAVIRT_SPINLOCKS seems to work OK these days, too. I'll leave that
set so I'll end up testing whatever comes along down that pipe...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
--
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/