[PATCH 1/1] scsi: storvsc: Reduce default ring buffer size to 128 Kbytes

[PATCH 1/1] scsi: storvsc: Reduce default ring buffer size to 128 Kbytes

[Michael Kelley]

Reduce the default VMbus channel ring buffer size for storvsc
SCSI devices from 1 Mbyte to 128 Kbytes. Measurements show
that ring buffer sizes above 128 Kbytes do not increase
performance even at very high IOPS rates, so don't waste
the memory. Also remove the dependence on PAGE_SIZE, since
the ring buffer size should not change on architectures
where PAGE_SIZE is not 4 Kbytes.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/scsi/storvsc_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index fbaa11a..f85517d 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -385,7 +385,7 @@ enum storvsc_request_type {
  * This is the end of Protocol specific defines.
  */
 
-static int storvsc_ringbuffer_size = (256 * PAGE_SIZE);
+static int storvsc_ringbuffer_size = (128 * 1024);
 static u32 max_outstanding_req_per_channel;
 
 static int storvsc_vcpus_per_sub_channel = 4;
-- 
1.8.3.1

RE: [PATCH 1/1] scsi: storvsc: Reduce default ring buffer size to 128 Kbytes

[Haiyang Zhang]

> -----Original Message-----
> From: linux-hyperv-owner@vger.kernel.org <linux-hyperv-
> owner@vger.kernel.org> On Behalf Of Michael Kelley
> Sent: Monday, April 1, 2019 5:42 PM
> To: KY Srinivasan <kys@microsoft.com>; martin.petersen@oracle.com; Long Li
> <longli@microsoft.com>; James.Bottomley@hansenpartnership.com;
> emilne@redhat.com; linux-hyperv@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-scsi@vger.kernel.org
> Cc: Michael Kelley <mikelley@microsoft.com>
> Subject: [PATCH 1/1] scsi: storvsc: Reduce default ring buffer size to 128 Kbytes
> 
> Reduce the default VMbus channel ring buffer size for storvsc SCSI devices
> from 1 Mbyte to 128 Kbytes. Measurements show that ring buffer sizes above
> 128 Kbytes do not increase performance even at very high IOPS rates, so don't
> waste the memory. Also remove the dependence on PAGE_SIZE, since the ring
> buffer size should not change on architectures where PAGE_SIZE is not 4 Kbytes.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>

Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Thank you.

Re: [PATCH 1/1] scsi: storvsc: Reduce default ring buffer size to 128 Kbytes

[Martin K. Petersen]

Michael,

> Reduce the default VMbus channel ring buffer size for storvsc SCSI
> devices from 1 Mbyte to 128 Kbytes. Measurements show that ring buffer
> sizes above 128 Kbytes do not increase performance even at very high
> IOPS rates, so don't waste the memory. Also remove the dependence on
> PAGE_SIZE, since the ring buffer size should not change on
> architectures where PAGE_SIZE is not 4 Kbytes.

Applied to 5.1/scsi-fixes, thanks.

-- 
Martin K. Petersen	Oracle Linux Engineering