Re: [Bugme-new] [Bug 10810] New: Performance regression on DAC960 and kernel 2.6.24+

[Andrew Morton <akpm@linux-foundation.org>]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Wed, 28 May 2008 03:52:37 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=10810
> 
>            Summary: Performance regression on DAC960 and kernel 2.6.24+
>            Product: IO/Storage
>            Version: 2.5
>      KernelVersion: 2.6.24, 2.6.25
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: high
>           Priority: P1
>          Component: Block Layer
>         AssignedTo: axboe@kernel.dk
>         ReportedBy: alex@nibbles.it
> 
> 
> Latest working kernel version:
> 2.6.23
> 
> Earliest failing kernel version:
> 2.6.24
> 
> Distribution:
> Debian
> 
> Hardware Environment:
> 00:00.0 RAM memory: nVidia Corporation C51 Host Bridge (rev a2)
> 00:00.1 RAM memory: nVidia Corporation C51 Memory Controller 0 (rev a2)
> 00:00.2 RAM memory: nVidia Corporation C51 Memory Controller 1 (rev a2)
> 00:00.3 RAM memory: nVidia Corporation C51 Memory Controller 5 (rev a2)
> 00:00.4 RAM memory: nVidia Corporation C51 Memory Controller 4 (rev a2)
> 00:00.5 RAM memory: nVidia Corporation C51 Host Bridge (rev a2)
> 00:00.6 RAM memory: nVidia Corporation C51 Memory Controller 3 (rev a2)
> 00:00.7 RAM memory: nVidia Corporation C51 Memory Controller 2 (rev a2)
> 00:02.0 PCI bridge: nVidia Corporation C51 PCI Express Bridge (rev a1)
> 00:03.0 PCI bridge: nVidia Corporation C51 PCI Express Bridge (rev a1)
> 00:04.0 PCI bridge: nVidia Corporation C51 PCI Express Bridge (rev a1)
> 00:05.0 VGA compatible controller: nVidia Corporation C51G [GeForce 6100] (rev
> a2)
> 00:09.0 RAM memory: nVidia Corporation MCP51 Host Bridge (rev a2)
> 00:0a.0 ISA bridge: nVidia Corporation MCP51 LPC Bridge (rev a2)
> 00:0a.1 SMBus: nVidia Corporation MCP51 SMBus (rev a2)
> 00:0b.0 USB Controller: nVidia Corporation MCP51 USB Controller (rev a2)
> 00:0b.1 USB Controller: nVidia Corporation MCP51 USB Controller (rev a2)
> 00:0d.0 IDE interface: nVidia Corporation MCP51 IDE (rev a1)
> 00:0e.0 IDE interface: nVidia Corporation MCP51 Serial ATA Controller (rev a1)
> 00:10.0 PCI bridge: nVidia Corporation MCP51 PCI Bridge (rev a2)
> 00:14.0 Bridge: nVidia Corporation MCP51 Ethernet Controller (rev a1)
> 00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
> HyperTransport Technology Configuration
> 00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address
> Map
> 00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM
> Controller
> 00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
> Miscellaneous Control
> 04:08.0 RAID bus controller: Mylex Corporation AcceleRAID 352/170/160 support
> Device (rev 02)
> 
> Software Environment:
> Debian Lenny 64bit
> 
> Problem Description:
> I/O Access is very slow on some condition, for example samba users can't write
> more than a few KB/sec on the shares.
> Also tomcat is veeeery slow to startup (at least 3 times the normal time).
> 
> Steps to reproduce:
> Simply boot with the new kernel

Oh dear.

There's been only one change to DAC960.c in that timeframe:

commit 0156c2547e92df559d5592aad9535838ef459615
Author: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Date:   Tue Dec 11 17:43:15 2007 -0500

    blk_end_request: changing DAC960 (take 4)
    
    This patch converts DAC960 to use blk_end_request interfaces.
    Related 'UpToDate' arguments are converted to 'Error'.
    
    Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
    Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

:100644 100644 9030c37... cd03473... M  drivers/block/DAC960.c

commit 117636092a87a28a013a4acb5de5492645ed620f
Author: Ralf Baechle <ralf@linux-mips.org>
Date:   Tue Oct 23 20:42:11 2007 +0200

    [PATCH] Fix breakage after SG cleanups

and I don't see how it could cause this.  The breakage is probably
external to the driver.

I don't know what it could be and I don't know anyone who can be asked
to look into it.

If you have time, the only way I can think of getting to the bottom of
this is if you were to run a git bisection search as per
http://www.kernel.org/doc/local/git-quick.html.  Sorry.