On Fri, Nov 15 2002, Steve Lord wrote:
> Jens,
>
> As you know, for the last week or so I have been battling some
> performance issues in XFS and 2.4.20-rc1. Well, we finally found
> the culprit back in 2.4.20-pre2.
>
> When the block highmem patch was included, it added highmem_io to the
> scsi controller structure. This can only ever be set to one if
> CONFIG_HIGHIO is set. Yet there are several spots in the scsi
> code which test based on its value regardless.
>
> /*
> * we really want to use sg even for a single segment request,
> * however some people just cannot be bothered to write decent
> * driver code so we can't risk to break somebody making the
> * assumption that sg requests will always contain at least 2
> * segments. if the driver is 32-bit dma safe, then use sg for
> * 1 entry anyways. if not, don't rely on the driver handling this
> * case.
> */
> if (count == 1 && !SCpnt->host->highmem_io) {
> this_count = req->current_nr_sectors;
> goto single_segment;
> }
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;
}
-- 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/
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