Message-ID: <8F120FA493CAD743B30EEB8F356985B5023FCA23@AUSXMBT102VS1.amer.dell.com>
From: Robert_Macaulay@Dell.com
To: Andrew.Bond@COMPAQ.com, linux-kernel@vger.kernel.org
Cc: Mike.Nikolaiev@COMPAQ.com, Jamshed.Patel@oracle.com
Subject: =?utf-8?B?UkU6IFtQQVRDSF0ga2lvYnVmX2luaXQgb3B0aW1pemF0aW9u?=
Date: Wed, 3 Oct 2001 18:48:23 -0500 
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We expierenced a panic when starting Oracle 8i with your patch(actually ac4)
right after the database was mounted. I will forward you the oops I posted
earlier today.

-----Original Message----- 
From: Bond, Andrew 
Sent: Wed 10/3/2001 4:47 PM 
To: linux-kernel@vger.kernel.org 
Cc: Nikolaiev, Mike; Jamshed Patel (E-mail) 
Subject: [PATCH] kiobuf_init optimization


        I have come up with a change to the kiobuf_init() routine that 
drops the blind memset() to 0 of the entire kiobuf structure and zeros 
out 3 specific fields instead.  Since this is done on every IO and the 
kiobuf structure is over 8K in size (8756 bytes I believe) it becomes 
quite costly from a cpu cycle perspective as well as a cache utilization 
perspective.  The typical IO path uses a small subset of the 
preallocated fields within the kiobuf structure.  Therefore, the IO path 
pays a performance penalty for having to zero out many fields that it 
typically doesn't use. 

        The kiobuf_init() routine using a memset() of the entire kiobuf 
structure is in the top 10 of cpu consuming kernel routines in Oracle 9i 
testing using raw io.  Using the included kiobuf_init patch, our testing 
has shown a 5% improvement in Oracle transactional performance in 4 and 
8 processor configurations, and the kiobuf_init() routine became a 
non-issue for performance.  The testing was performed with Oracle, but 
this patch could provide performance improvements to any application 
that uses raw IO or relies on kiobufs in the IO path. 

        Obviously, since the structure is no longer set to zero, any 
code that makes a zero assumption would break.  I haven't come across 
code that makes this assumption yet for fields that I did not 
specifically zero out in the patch, but I could very well be missing 
something.  It appears that Alan has included this patch in his 
2.4.10-ac4 tree.  So, let me know if you have any problems that you 
think might be related to this patch.   Any input would be greatly 
appreciated. 

        The patch is against a 2.4.9 tree, but it is localized to just 
the kiobuf_init() routine and should apply to any of the recent kernels. 

        Run from the root level of your kernel tree:  
                patch -p1 < kiobuf_init_speedup.patch 

        I cannot currently receive the kernel mailing list at this email 
address, so please cc: me on posts related to this patch. 

Thanks, 
Andrew Bond 

 <<kiobuf_init_speedup.patch>> 


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