From: Nikhil Kshirsagar <nkshirsagar@gmail.com>
To: linux-bcache@vger.kernel.org
Cc: Coly Li <colyli@suse.de>
Subject: bcache I/O performance tests on 5.15.0-40-generic
Date: Sat, 25 Jun 2022 11:59:13 +0530 [thread overview]
Message-ID: <CAC6jXv0FoE60HEuc7tDMXEA27hkoMkZm5d6gt4NCRkAh2w3WvA@mail.gmail.com> (raw)
Hello,
I've been doing some performance tests of bcache on 5.15.0-40-generic.
The baseline figures for the fast and slow disk for random writes are
consistent at around 225MiB/s and 3046KiB/s.
But the bcache results inexplicably drop sometimes to 10Mib/s, for
random write test using fio like this -
fio --rw=randwrite --size=1G --ioengine=libaio --direct=1
--gtod_reduce=1 --iodepth=128 --bs=4k --name=MY_TEST1
WRITE: bw=168MiB/s (176MB/s), 168MiB/s-168MiB/s (176MB/s-176MB/s),
io=1024MiB (1074MB), run=6104-6104msec
WRITE: bw=283MiB/s (297MB/s), 283MiB/s-283MiB/s (297MB/s-297MB/s),
io=1024MiB (1074MB), run=3621-3621msec
WRITE: bw=10.3MiB/s (10.9MB/s), 10.3MiB/s-10.3MiB/s
(10.9MB/s-10.9MB/s), io=1024MiB (1074MB), run=98945-98945msec
WRITE: bw=8236KiB/s (8434kB/s), 8236KiB/s-8236KiB/s
(8434kB/s-8434kB/s), io=1024MiB (1074MB), run=127317-127317msec
WRITE: bw=9657KiB/s (9888kB/s), 9657KiB/s-9657KiB/s
(9888kB/s-9888kB/s), io=1024MiB (1074MB), run=108587-108587msec
WRITE: bw=4543KiB/s (4652kB/s), 4543KiB/s-4543KiB/s
(4652kB/s-4652kB/s), io=1024MiB (1074MB), run=230819-230819msec
This seems to happen after 2 runs of 1gb writes (cache disk is 4gb size)
Some details are here - https://pastebin.com/V9mpLCbY , I will share
the full testing results soon, but just was wondering about this
performance drop for no apparent reason once the cache gets about 50%
full.
I've tested in writeback mode, and also set
congested_read_threshold_us and congested_write_threshold_us to 0
I did not notice this issue while testing on an older kernel -
4.15.0-188-generic
Regards,
Nikhil.
next reply other threads:[~2022-06-25 6:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-25 6:29 Nikhil Kshirsagar [this message]
2022-06-25 12:08 ` bcache I/O performance tests on 5.15.0-40-generic Coly Li
2022-06-30 4:24 ` Nikhil Kshirsagar
[not found] ` <CAC6jXv0yOZ98XqG=quDcONuZ9ggqK4doM8EzVTc=Sk1m-H=_Xw@mail.gmail.com>
2022-06-30 6:49 ` Coly Li
[not found] ` <CAC6jXv2u_0s-hvj4J4gurfoxgKNHFcHYq9F8cfcf-s6oG+pU+Q@mail.gmail.com>
2022-06-30 7:36 ` Coly Li
2022-06-30 7:39 ` Nikhil Kshirsagar
2022-06-30 7:47 ` Coly Li
2022-07-05 20:49 ` Eric Wheeler
2022-07-28 15:51 ` Coly Li
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