Hrm, on second thought I suspect it's just more seeks on disk. Maybe
blktrace would be more useful.
Mark
On 8/24/20 2:03 PM, Mark Nelson wrote:
Hi Igor,
If it is easily reproducible, could you run each test with gdbpmp so
we can observe where time is being spent?
Mark
On 8/24/20 9:26 AM, Igor Fedotov wrote:
Hi All,
I've just completed a small investigation on this issue.
Short summary for Abutalib's benchmark scenario in my environment:
- when "vstarted" cluster has WAL/DB at NVMe drive - master is ~65%
faster (130 MB/s vs. 75MB/s)
- in spinner-only setup (WAL/DB are at the same spinner) - octopus is
70 % faster than master ( 88MB/s vs. 52 MB/s)
Looks like it is bluestore_max_blob_size_hdd set to 64K by default
which causes performance drop in this case (commit sha
a8733598eddf57dca86bf002653e630a7cf4db6e).
Setting it back to 512K results in a better performance for master:
113 MB/s vs. 88 MB/s
But I presume these numbers are tightly bound to writing 4MB chunks
benchmark scenario. Different chunk size will most probably cause
pretty different results. Hence reverting bluestore_max_blob_size_hdd
back to 512K by default is IMO still questionable.
Wondering if the above results are in-line with somebody's else ones....
Thanks,
Igor
On 8/4/2020 6:29 AM, Abutalib Aghayev wrote:
Hi all,
There appears to be a performance regression going from 15.2.4 to
HEAD. I first realized this when testing my patches to Ceph on an
8-node cluster, but it is easily reproducible on *vanilla* Ceph with
vstart as well, using the following steps:
$ git clone https://github.com/ceph/ceph.git && cd ceph
$ ./do_cmake.sh -DCMAKE_BUILD_TYPE=RelWithDebInfo -DWITH_MANPAGE=OFF
-DWITH_BABELTRACE=OFF -DWITH_MGR_DASHBOARD_FRONTEND=OFF && cd build
&& make -j32 vstart
$ MON=1 OSD=1 MDS=0 ../src/vstart.sh --debug --new --localhost
--bluestore --bluestore-devs /dev/xxx
$ sudo ./bin/ceph osd pool create foo 32 32
$ sudo ./bin/rados bench -p foo 100 write --no-cleanup
With the old hard drive that I have (Hitachi HUA72201), I'm getting
an average throughput of 60 MiB/s. When I switch to v15.2.4 (git
checkout v15.2.4), rebuild, and repeat the experiment, and I get an
average throughput of 90 MiB/s. I've reliably reproduced similar
difference between 15.2.4 and HEAD by building release packages and
running them on an 8-node cluster.
Is this expected or is this a performance regression?
Thanks!
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