On Tue, Oct 24, 2017 at 10:40 AM, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> Here is V12 of the hardware command queue patches without the software
> command queue patches, now using blk-mq and now with blk-mq support for
> non-CQE I/O.
Since I had my test setup going I gave this a spin with the same set
of tests that I used before/after my MQ patches.
It is using the same setup and same eMMC, but I hade to rebase onto
Ulf's very latest next branch to apply your patches.
I default-enabled multiqueue.
Results:
sync
echo 3 > /proc/sys/vm/drop_caches
sync
time dd if=/dev/mmcblk3 of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.0GB) copied, 24.251922 seconds, 42.2MB/s
real 0m 24.25s
user 0m 0.03s
sys 0m 3.80s
mount /dev/mmcblk3p1 /mnt/
cd /mnt/
sync
echo 3 > /proc/sys/vm/drop_caches
sync
time find . > /dev/null
real 0m 3.24s
user 0m 0.22s
sys 0m 1.23s
sync
echo 3 > /proc/sys/vm/drop_caches
sync
iozone -az -i0 -i1 -i2 -s 20m -I -f /mnt/foo.test
random random
kB reclen write rewrite read reread read write
20480 4 1615 1571 6612 6714 6494 531
20480 8 2143 2295 11559 11563 11499 1164
20480 16 3894 4202 17826 17823 17755 1369
20480 32 5816 7489 23741 23759 23709 3016
20480 64 7393 9167 27532 27526 27502 3591
20480 128 7328 8097 29184 29161 29159 5592
20480 256 7194 8752 29424 29434 29424 6700
20480 512 8984 9930 29903 29911 29909 7420
20480 1024 7072 7446 27684 27685 27681 7444
20480 2048 6840 8199 27398 27420 27418 6766
20480 4096 8137 6805 28091 28089 28093 8209
20480 8192 7255 7485 28386 28384 28383 7479
20480 16384 7078 7448 28584 28585 28585 7447
In short: no performance regressions.
Performance-wise this is on par with my own patch set for MQ.
As you know my pet peeve is "enable MQ by default" and I see no
reason from a performance perspective not to enable MQ by default
on this patch set or mine for that matter.
> While we should look at changing blk-mq to give better workqueue performance,
> a bigger gain is likely to be made by adding a new host API to enable the
> next already-prepared request to be issued directly from within ->done()
> callback of the current request.
My patch series switches the stack around to make it possible
to do this. But it doesn't go the whole way to complete the requests
from interrupt context.
Since we have to send commands for retune etc request finalization
cannot easily be done from interrupt context.
But I am thinking about testing to hack it
using some ugly approaches ... like assuming we don't need any
retune etc and just say all is fine and optimistically complete the
request directly in the interrupt handler if all was OK and wait
for errors to happen before retuning.
Yours,
Linus Walleij
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