[lkml]   [2019]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRE: [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, wrote:
>>From: Long Li <>
>>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 <>
>>v2: rely on default upper layer function to map queues. (suggested by
>>Ming Lei
>>v3: use num_present_cpus() instead of num_online_cpus(). Hyper-v
>>doesn't support hot-add CPUs. (suggested by Michael Kelley
>>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.


 \ /
  Last update: 2019-09-06 23:37    [W:0.064 / U:47.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site