Re: [PATCH v3 4/4] scsi: use percpu counters for iostat counters in struct scsi_device

Hannes Reinecke <[email protected]> Wed, 10 Jun 2026 08:21:07 +0200

Newsgroups	org.kernel.vger.target-devel,dev.linux.lists.virtualization,org.kernel.vger.linux-block,org.kernel.vger.linux-hyperv,org.kernel.vger.linux-scsi,org.ozlabs.lists.linuxppc-dev,org.xenproject.lists.xen-devel
Message-ID	<[email protected]>

On 6/9/26 14:18, Sumit Saxena wrote:
> iorequest_cnt and iodone_cnt are updated on every command dispatch and
> completion, often from different CPUs on high queue depth workloads.
> Using adjacent atomic_t fields causes cache line contention between the
> submission and completion paths.
> 
> Extend the same treatment to ioerr_cnt and iotmo_cnt so all four iostat
> counters in struct scsi_device use struct percpu_counter.
> 
> Suggested-by: John Garry <[email protected]>
> Signed-off-by: Sumit Saxena <[email protected]>
> ---
>   drivers/scsi/scsi_error.c  |  4 ++--
>   drivers/scsi/scsi_lib.c    | 10 +++++-----
>   drivers/scsi/scsi_scan.c   |  8 ++++++++
>   drivers/scsi/scsi_sysfs.c  | 23 ++++++++++++++---------
>   drivers/scsi/sd.c          |  2 +-
>   include/scsi/scsi_device.h |  9 +++++----
>   6 files changed, 35 insertions(+), 21 deletions(-)
> 
Good idea.

Reviewed-by: Hannes Reinecke <[email protected]>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
[email protected]                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich