Messages in this thread | | | From | "Michael Kelley (EOSG)" <> | Subject | RE: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a channel for I/O requests | Date | Wed, 31 Jan 2018 21:14:26 +0000 |
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> From: Long Li > Sent: Wednesday, January 31, 2018 12:23 PM > To: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>; KY Srinivasan > <kys@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com>; > martin.petersen@oracle.com; devel@linuxdriverproject.org; linux-kernel@vger.kernel.org; > linux-scsi@vger.kernel.org; James E . J . Bottomley <jejb@linux.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@microsoft.com>; Stephen Hemminger > > > <sthemmin@microsoft.com>; martin.petersen@oracle.com; > > > longi@microsoft.com; JBottomley@odin.com; > > > devel@linuxdriverproject.org; linux-kernel@vger.kernel.org; > > > linux-scsi@vger.kernel.org > > > Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.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@microsoft.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.
Yes, it works. for_each_cpu_wrap() correctly wraps in the case where the 3rd parameter ('start') is one past the end of the mask. Arguably, we shouldn't rely on that, and should do the wrap to 0 before calling for_each_cpu_wrap().
> > > > if (tgt_cpu != outgoing_channel->target_cpu) > > { > > > outgoing_channel = > > > stor_device->stor_chns[tgt_cpu]; > > > -- > > > 1.8.3.1
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