Re: [patch] zero-bounce block highmem I/O, #13

From: Jens Axboe (axboe@suse.de)
Date: Tue Aug 28 2001 - 06:41:41 EST

On Tue, Aug 28 2001, Jens Axboe wrote:
> On Tue, Aug 28 2001, Christoph Rohland wrote:
> > Hi Jens,
> >
> > I tested both #11 and #13 on my 8GB machine with sym53c8xx. The
> > initialization of a SAP DB database takes 20 minutes with 2.4.9 and
> > with 2.4.9+b13 it took nearly 2.5 hours :-(
>
> DaveM hinted that it's probably the bounce test failing, so it's
> bouncing all the time. That would explain the much worse performance.
> Could you try with this incremental patch on top of b13 for 2.4.9? I
> still want to see the boot detection info, btw.
>
> THanks!

Ok found the bug -- SCSI was accidentally using blk_seg_merge_ok when it
just wanted to test if we were crossing a 4GB physical address boundary
or not. Doh! Attached incremental patch should fix the SCSI performance
issue. I'm testing right now... 

-- 
Jens Axboe
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