linux-kernel - Re: AIM7 40% regression with 2.6.26-rc1

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Message-ID: <20080508092102.GA32164@elte.hu>
Date:	Thu, 8 May 2008 11:21:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Matthew Wilcox <matthew@....cx>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexander Viro <viro@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: AIM7 40% regression with 2.6.26-rc1


* Zhang, Yanmin <yanmin_zhang@...ux.intel.com> wrote:

> >           disk_cp /mnt/shm
> >   disk_cp (1): cannot open /mnt/shm/tmpa.common
> >   disk1.c: No such file or directory
> > 
> >   [.. etc. a large stream of them .. ]
> > 
> > system has 2GB of RAM and tmpfs mounted to the place where aim7 puts its 
> > work files.

> My machine has 8GB. To simulate your environment, I reserve 6GB for 
> hugetlb, then reran the testing and didn't see any failure except: AIM 
> Multiuser Benchmark - Suite VII Run Beginning
> 
> Tasks    jobs/min  jti  jobs/min/task      real       cpu
>  2000create_shared_memory(): can't create semaphore, pausing...
> create_shared_memory(): can't create semaphore, pausing...

that failure message you got worries me - it indicates that your test 
ran out of IPC semaphores. You can fix it via upping the semaphore 
limits via:

   echo "500 32000 128 512" > /proc/sys/kernel/sem

could you check that you still get similar results with this limit 
fixed?

note that once i've fixed the semaphore limits it started running fine 
here. And i see zero idle time during the run on a quad core box.

here are my numbers:

  # on v2.6.26-rc1-166-gc0a1811

  Tasks   Jobs/Min        JTI     Real    CPU     Jobs/sec/task
  2000    55851.4         93      208.4   793.6   0.4654   # BKL: sleep
  2000    55402.2         79      210.1   800.1   0.4617

  2000    55728.4         93      208.9   795.5   0.4644   # BKL: spin
  2000    55787.2         93      208.7   794.5   0.4649   #

so the results are the same within noise.

I'll also check this workload on an 8-way box to make sure it's OK on 
larger CPU counts too.

could you double-check your test?

plus a tty tidbit as well, during the test i saw a few of these:

 Warning: dev (tty1) tty->count(639) != #fd's(638) in release_dev
 Warning: dev (tty1) tty->count(462) != #fd's(463) in release_dev
 Warning: dev (tty1) tty->count(274) != #fd's(275) in release_dev
 Warning: dev (tty1) tty->count(4) != #fd's(3) in release_dev
 Warning: dev (tty1) tty->count(164) != #fd's(163) in release_dev

	Ingo
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