Re: SCSI I/O performance problems when CONFIG_HIGHIO is off

From: Jens Axboe (axboe@suse.de)
Date: Mon Nov 18 2002 - 09:12:37 EST


On Mon, Nov 18 2002, Stephen Lord wrote:
> On Mon, 2002-11-18 at 06:05, Jens Axboe wrote:
>
> >
> > Steve,
> >
> > Something isn't quite making sense. If we go over every single instance
> > of checking ->highmem_io, they all look sane (ie checking on non-highmem
> > setup must yield 0). So that part looks good.
> >
> > However, I think a typo snuck in there, in exactly the spot you pasted
> > above. Could you try 2.4.20-rc2 with this patch applied?
> >
> > ===== drivers/scsi/scsi_merge.c 1.9 vs edited =====
> > --- 1.9/drivers/scsi/scsi_merge.c Mon Sep 16 09:25:10 2002
> > +++ edited/drivers/scsi/scsi_merge.c Mon Nov 18 13:04:41 2002
> > @@ -835,7 +835,7 @@
> > * case.
> > */
> > if (count == 1 && !SCpnt->host->highmem_io) {
> > - this_count = req->current_nr_sectors;
> > + this_count = req->nr_sectors;
> > goto single_segment;
> > }
>
> That looks like it does it, performance is pretty much what I was
> getting with HIGHIO on.

Great, thanks for verifying that. I'll push it to Marcelo ASAP.

-- 
Jens Axboe

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Sat Nov 23 2002 - 22:00:22 EST