NVMe: Adhere to request queue block accounting enable/disable
authorSam Bradshaw <sbradshaw@micron.com>
Fri, 9 May 2014 20:27:07 +0000 (13:27 -0700)
committerMatthew Wilcox <matthew.r.wilcox@intel.com>
Wed, 4 Jun 2014 02:58:54 +0000 (22:58 -0400)
commitb4e75cbf1364c4bbce3599c3279892a55b6ede07
tree9387e92ae6a0b2e6e491e3332c2d89d3a5b95469
parenta51afb54339c5e9ee72df66ae0f2ac5aacfed365
NVMe: Adhere to request queue block accounting enable/disable

Recently, a new sysfs control "iostats" was added to selectively
enable or disable io statistics collection for request queues.  This
patch hooks that control.

IO statistics collection is rather expensive on large, multi-node
machines with drives pushing millions of iops.  Having the ability to
disable collection if not needed can improve throughput significantly.

As a data point, on a quad E5-4640, I see more than 50% throughput
improvement when io statistics accounting is disabled during heavily
multi-threaded small block random read benchmarks where device
performance is in the million iops+ range.

Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
drivers/block/nvme-core.c