linux-kernel - RE: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a channel for I/O requests

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Date:   Wed, 31 Jan 2018 20:22:58 +0000
From:   Long Li <longli@...rosoft.com>
To:     "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>
Subject: RE: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a
 channel for I/O requests

> Subject: RE: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a
> channel for I/O requests
> 
> Updated/corrected two email addresses ...
> 
> > -----Original Message-----
> > From: Michael Kelley (EOSG)
> > Sent: Wednesday, January 24, 2018 2:14 PM
> > To: KY Srinivasan <kys@...rosoft.com>; Stephen Hemminger
> > <sthemmin@...rosoft.com>; martin.petersen@...cle.com;
> > longi@...rosoft.com; JBottomley@...n.com;
> > devel@...uxdriverproject.org; linux-kernel@...r.kernel.org;
> > linux-scsi@...r.kernel.org
> > Cc: Michael Kelley (EOSG) <Michael.H.Kelley@...rosoft.com>
> > Subject: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a
> > channel for I/O requests
> >
> > Update the algorithm in storvsc_do_io to look for a channel starting
> > with the current CPU + 1 and wrap around (within the current NUMA
> > node). This spreads VMbus interrupts more evenly across CPUs. Previous
> > code always started with first CPU in the current NUMA node, skewing
> > the interrupt load to that CPU.
> >
> > Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> > ---
> >  drivers/scsi/storvsc_drv.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index e07907d..f3264c4 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1310,7 +1310,8 @@ static int storvsc_do_io(struct hv_device *device,
> >  			 */
> >  			cpumask_and(&alloced_mask, &stor_device-
> >alloced_cpus,
> >
> cpumask_of_node(cpu_to_node(q_num)));
> > -			for_each_cpu(tgt_cpu, &alloced_mask) {
> > +			for_each_cpu_wrap(tgt_cpu, &alloced_mask,
> > +					outgoing_channel->target_cpu + 1) {

Does it work when target_cpu is the last CPU on the system?

Otherwise, looking good.

> >  				if (tgt_cpu != outgoing_channel->target_cpu)
> {
> >  					outgoing_channel =
> >  					stor_device->stor_chns[tgt_cpu];
> > --
> > 1.8.3.1