Hi,
We have noticed a performance regression in kernel with fio sequential
write job.
Notes and observations:
======================
1. This is observed on recent kernels(6.6) when compared with 5.15.y,
the bisection points to commit d47f9717e5cf ("block/mq-deadline: use
correct way to throttling write requests")
2. Reverting the above commit improves the performance.
3. This regression can also be seen on 6.8-rc7 and a revert on top of
that fixes the regression.
4. The commit looks very much related to the cause of regression.
5. Note that this happens only with multi-path setup even with 2 block
devices.
Test details:
============
(A) fio.write job
fio-3.19 -- fio version
[global]
ioengine=libaio
rw=write
bs=128k
iodepth=64
numjobs=24
direct=1
fsync=1
runtime=600
group_reporting
[job]
filename=/dev/dm-0
[job]
filename=/dev/dm-1
Each disk is of 600G size.
(B) Test results
6.8-rc7: 2 block devices with multi-path
-------
job: (g=0): rw=write, bs=(R) 128KiB-128KiB, (W) 128KiB-128KiB, (T)
128KiB-128KiB, ioengine=libaio, iodepth=64
...
job: (g=0): rw=write, bs=(R) 128KiB-128KiB, (W) 128KiB-128KiB, (T)
128KiB-128KiB, ioengine=libaio, iodepth=64
...
fio-3.19
Starting 48 processes
job: (groupid=0, jobs=48): err= 0: pid=6164: Wed Mar 6 17:58:33 2024
write: IOPS=1884, BW=236MiB/s (247MB/s)(138GiB/600319msec); 0 zone resets
slat (usec): min=2, max=540462, avg=25445.35, stdev=24181.85
clat (msec): min=9, max=4941, avg=1602.56, stdev=339.05
lat (msec): min=9, max=4973, avg=1628.00, stdev=342.19
clat percentiles (msec):
| 1.00th=[ 986], 5.00th=[ 1167], 10.00th=[ 1250], 20.00th=[ 1368],
| 30.00th=[ 1435], 40.00th=[ 1502], 50.00th=[ 1569], 60.00th=[ 1636],
| 70.00th=[ 1703], 80.00th=[ 1804], 90.00th=[ 1955], 95.00th=[ 2140],
| 99.00th=[ 2869], 99.50th=[ 3239], 99.90th=[ 3842], 99.95th=[ 4010],
| 99.99th=[ 4329]
bw ( KiB/s): min=47229, max=516492, per=100.00%, avg=241546.47,
stdev=1326.92, samples=57259
iops : min= 322, max= 3996, avg=1843.17, stdev=10.39,
samples=57259
lat (msec) : 10=0.01%, 20=0.01%, 50=0.01%, 100=0.01%, 250=0.02%
lat (msec) : 500=0.06%, 750=0.14%, 1000=0.93%, 2000=90.41%,
>=2000=8.42%
fsync/fdatasync/sync_file_range:
sync (nsec): min=10, max=57940, avg=104.23, stdev=498.86
sync percentiles (nsec):
| 1.00th=[ 13], 5.00th=[ 19], 10.00th=[ 26], 20.00th=[ 61],
| 30.00th=[ 68], 40.00th=[ 72], 50.00th=[ 75], 60.00th=[ 78],
| 70.00th=[ 87], 80.00th=[ 167], 90.00th=[ 175], 95.00th=[ 177],
| 99.00th=[ 221], 99.50th=[ 231], 99.90th=[ 318], 99.95th=[15680],
| 99.99th=[17792]
cpu : usr=0.08%, sys=0.16%, ctx=1096948, majf=0, minf=1995
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%,
>=64=199.5%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,
>=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%,
>=64=0.0%
issued rwts: total=0,1131018,0,1127994 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=64
Run status group 0 (all jobs):
WRITE: bw=236MiB/s (247MB/s), 236MiB/s-236MiB/s (247MB/s-247MB/s),
io=138GiB (148GB), run=600319-600319msec
Disk stats (read/write):
dm-0: ios=50/533034, merge=0/27056, ticks=16/113070163,
in_queue=113070180, util=100.00%, aggrios=43/266595, aggrmerge=0/0,
aggrticks=156/56542549, aggrin_queue=56542706, aggrutil=100.00%
sdac: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
sde: ios=86/533191, merge=0/0, ticks=313/113085099,
in_queue=113085413, util=100.00%
dm-1: ios=5/534381, merge=0/36389, ticks=240/113110344,
in_queue=113110584, util=100.00%, aggrios=7/267191, aggrmerge=0/0,
aggrticks=153/56543654, aggrin_queue=56543807, aggrutil=100.00%
sdf: ios=14/534382, merge=0/0, ticks=306/113087308,
in_queue=113087615, util=100.00%
sdad: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
Throughput Results:
WRITE:247:1884:0
6.8-rc7+ Revert : 2 block devices with multi-path
-------
job: (g=0): rw=write, bs=(R) 128KiB-128KiB, (W) 128KiB-128KiB, (T)
128KiB-128KiB, ioengine=libaio, iodepth=64
...
job: (g=0): rw=write, bs=(R) 128KiB-128KiB, (W) 128KiB-128KiB, (T)
128KiB-128KiB, ioengine=libaio, iodepth=64
...
fio-3.19
Starting 48 processes
job: (groupid=0, jobs=48): err= 0: pid=6104: Wed Mar 6 18:29:13 2024
write: IOPS=2518, BW=315MiB/s (330MB/s)(185GiB/600339msec); 0 zone resets
slat (usec): min=2, max=923472, avg=6789.22, stdev=20329.20
clat (msec): min=4, max=6020, avg=1212.68, stdev=714.90
lat (msec): min=4, max=6020, avg=1219.47, stdev=718.40
clat percentiles (msec):
| 1.00th=[ 203], 5.00th=[ 309], 10.00th=[ 384], 20.00th=[ 535],
| 30.00th=[ 709], 40.00th=[ 911], 50.00th=[ 1133], 60.00th=[ 1334],
| 70.00th=[ 1519], 80.00th=[ 1754], 90.00th=[ 2198], 95.00th=[ 2601],
| 99.00th=[ 3171], 99.50th=[ 3608], 99.90th=[ 4329], 99.95th=[ 4597],
| 99.99th=[ 5134]
bw ( KiB/s): min=12237, max=1834896, per=100.00%, avg=413187.52,
stdev=6322.04, samples=44948
iops : min= 48, max=14314, avg=3186.68, stdev=49.49,
samples=44948
lat (msec) : 10=0.01%, 20=0.01%, 50=0.09%, 100=0.02%, 250=2.28%
lat (msec) : 500=15.45%, 750=14.26%, 1000=11.83%, 2000=42.52%,
>=2000=13.55%
fsync/fdatasync/sync_file_range:
sync (nsec): min=10, max=76066, avg=57.85, stdev=299.52
sync percentiles (nsec):
| 1.00th=[ 13], 5.00th=[ 14], 10.00th=[ 15], 20.00th=[ 16],
| 30.00th=[ 17], 40.00th=[ 20], 50.00th=[ 28], 60.00th=[ 47],
| 70.00th=[ 65], 80.00th=[ 80], 90.00th=[ 103], 95.00th=[ 175],
| 99.00th=[ 237], 99.50th=[ 241], 99.90th=[ 262], 99.95th=[ 318],
| 99.99th=[16512]
cpu : usr=0.06%, sys=0.07%, ctx=531434, majf=0, minf=728
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%,
>=64=199.6%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,
>=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%,
>=64=0.0%
issued rwts: total=0,1511918,0,1508894 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=64
Run status group 0 (all jobs):
WRITE: bw=315MiB/s (330MB/s), 315MiB/s-315MiB/s (330MB/s-330MB/s),
io=185GiB (198GB), run=600339-600339msec
Disk stats (read/write):
dm-0: ios=0/246318, merge=0/493981, ticks=0/142584585,
in_queue=142584586, util=99.17%, aggrios=6/181454, aggrmerge=0/0,
aggrticks=112/70608689, aggrin_queue=70608801, aggrutil=84.92%
sdac: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
sde: ios=12/362908, merge=0/0, ticks=224/141217379,
in_queue=141217603, util=84.92%
dm-1: ios=0/233211, merge=0/538097, ticks=0/142579042,
in_queue=142579043, util=99.15%, aggrios=8/174475, aggrmerge=0/0,
aggrticks=128/70654686, aggrin_queue=70654814, aggrutil=85.20%
sdf: ios=16/348951, merge=0/0, ticks=256/141309372,
in_queue=141309628, util=85.20%
sdad: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
Throughput Results:
WRITE:330:2518:0
(C) performance difference:
That is roughly a 33.65% performance change, this is reproducible on
higher number of block devices as well.
Thanks to Paul Webb for identifying this regression and sharing the details.
We will be happy to test any patches to check the change in performance
and also follow any suggestions.
Thanks,
Harshit
