>Subject: RE: [Patch v4] storvsc: setup 1:1 mapping between hardware queue >and CPU queue > >>Subject: Re: [Patch v4] storvsc: setup 1:1 mapping between hardware >>queue and CPU queue >> >>On Fri, Sep 06, 2019 at 10:24:20AM -0700, longli@xxxxxxxxxxxxxxxxx wrote: >>>From: Long Li <longli@xxxxxxxxxxxxx> >>> >>>storvsc doesn't use a dedicated hardware queue for a given CPU queue. >>>When issuing I/O, it selects returning CPU (hardware queue) >>>dynamically based on vmbus channel usage across all channels. >>> >>>This patch advertises num_present_cpus() as number of hardware queues. >>>This will have upper layer setup 1:1 mapping between hardware queue >>>and CPU queue and avoid unnecessary locking when issuing I/O. >>> >>>Signed-off-by: Long Li <longli@xxxxxxxxxxxxx> Hi Martin, I have addressed all comments on this patch. Can you merge it to SCSI? If there is anything else I need to change, please let me know. Thanks Long >>>--- >>> >>>Changes: >>>v2: rely on default upper layer function to map queues. (suggested by >>>Ming Lei >>><tom.leiming@xxxxxxxxx>) >>>v3: use num_present_cpus() instead of num_online_cpus(). Hyper-v >>>doesn't support hot-add CPUs. (suggested by Michael Kelley >>><mikelley@xxxxxxxxxxxxx>) >>>v4: move change logs to after Signed-of-by >>> >>> drivers/scsi/storvsc_drv.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>>diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c >>>index b89269120a2d..cf987712041a 100644 >>>--- a/drivers/scsi/storvsc_drv.c >>>+++ b/drivers/scsi/storvsc_drv.c >>>@@ -1836,8 +1836,7 @@ static int storvsc_probe(struct hv_device *device, >>> /* >>> * Set the number of HW queues we are supporting. >>> */ >>>- if (stor_device->num_sc != 0) >>>- host->nr_hw_queues = stor_device->num_sc + 1; >>>+ host->nr_hw_queues = num_present_cpus(); >> >>Just looking at the change notes for v3: why isn't this >>num_active_cpus() then? One can still isolate CPUs on hyper-v, no? > >The isolated CPU can be made online at run time. For example, even >maxcpus=x is put on the boot line, individual CPUs can still be made >online/offline. > >> >>-- >>Thanks, >>Sasha
