Re: [PATCHSET RFC v2 0/5] Cache issue side time querying

[Jens Axboe <axboe@kernel.dk>]

On 1/16/24 9:54 AM, Jens Axboe wrote:
> Results in patch 2, but tldr is a more than 9% improvement (108M -> 118M
> IOPS) for my test case, which doesn't even enable most of the costly
> block layer items that you'd typically find in a distro and which would
> further increase the number of issue side time calls. This brings iostats
> enabled _almost_ to the level of turning it off.

Enabled the typical distro things (block cgroups, blk-wbt, iocost,
iolatency) which all add considerable cost (and is an optimization
project in itself) and this is the performance of the stock kernel with
iostats enabled:

IOPS=91.01M, BW=44.44GiB/s, IOS/call=32/32
IOPS=91.29M, BW=44.58GiB/s, IOS/call=31/32
IOPS=91.27M, BW=44.57GiB/s, IOS/call=32/31
IOPS=91.26M, BW=44.56GiB/s, IOS/call=32/31
IOPS=91.38M, BW=44.62GiB/s, IOS/call=32/31
IOPS=91.28M, BW=44.57GiB/s, IOS/call=32/32

which is down from 122M for an optimized config and with iostats off.
With this patchset applied (and one extra patch, missed a spot...), we
now get:

IOPS=101.38M, BW=49.50GiB/s, IOS/call=32/32
IOPS=101.31M, BW=49.47GiB/s, IOS/call=32/32
IOPS=101.35M, BW=49.49GiB/s, IOS/call=31/31
IOPS=101.44M, BW=49.53GiB/s, IOS/call=32/31
IOPS=101.32M, BW=49.47GiB/s, IOS/call=32/32
IOPS=101.14M, BW=49.38GiB/s, IOS/call=32/31

which is about a 10% improvement. Mostly ran this because I was curious,
and while the above config changes do add more time stamping, it also
adds additional overhead. In any case, 10% win for the distro config
case is not bad at all.

-- 
Jens Axboe