Hi Yoann,
FWIW, on CentOS7 I actually saw a performance increase when upgrading
from the stock 3.10 kernel to 4.4.5 with Intel P3700 NVMe devices. I
was encountering some kind of strange concurrency/locking issues at the
driver level that 4.4.5 resolved. I think your best bet is to try
different intermediate kernels, track it down as much as you can and
then look through the kernel changelog.
Sorry I can't be of more help!
Mark
On 07/25/2016 10:45 AM, Yoann Moulin wrote:
Hello,
(this is a repost, my previous message seems to be slipping under the radar)
Does anyone get a similar behaviour to the one described below ?
I found a big performance drop between kernel 3.13.0-88 (default kernel on
Ubuntu Trusty 14.04) or kernel 4.2.0 and kernel 4.4.0.24.14 (default kernel on
Ubuntu Xenial 16.04)
- ceph version is Jewel (10.2.2).
- All tests have been done under Ubuntu 14.04 on
- Each cluster has 5 nodes strictly identical.
- Each node has 10 OSDs.
- Journals are on the disk.
Kernel 4.4 has a drop of more than 50% compared to 4.2
Kernel 4.4 has a drop of 40% compared to 3.13
details below :
With the 3 kernel I have the same performance on disks :
Raw benchmark:
dd if=/dev/zero of=/dev/sdX bs=1M count=1024 oflag=direct => average ~230MB/s
dd if=/dev/zero of=/dev/sdX bs=1G count=1 oflag=direct => average ~220MB/s
Filesystem mounted benchmark:
dd if=/dev/zero of=/sdX1/test.img bs=1G count=1 => average ~205MB/s
dd if=/dev/zero of=/sdX1/test.img bs=1G count=1 oflag=direct => average ~214MB/s
dd if=/dev/zero of=/sdX1/test.img bs=1G count=1 oflag=sync => average ~190MB/s
Ceph osd Benchmark:
Kernel 3.13.0-88-generic : ceph tell osd.ID bench => average ~81MB/s
Kernel 4.2.0-38-generic : ceph tell osd.ID bench => average ~109MB/s
Kernel 4.4.0-24-generic : ceph tell osd.ID bench => average ~50MB/s
I did new benchmarks then on 3 new fresh clusters.
- Each cluster has 3 nodes strictly identical.
- Each node has 10 OSDs.
- Journals are on the disk.
bench5 : Ubuntu 14.04 / Ceph Infernalis
bench6 : Ubuntu 14.04 / Ceph Jewel
bench7 : Ubuntu 16.04 / Ceph jewel
this is the average of 2 runs of "ceph tell osd.* bench" on each cluster (2 x 30
OSDs)
bench5 / 14.04 / Infernalis / kernel 3.13 : 54.35 MB/s
bench6 / 14.04 / Jewel / kernel 3.13 : 86.47 MB/s
bench5 / 14.04 / Infernalis / kernel 4.2 : 63.38 MB/s
bench6 / 14.04 / Jewel / kernel 4.2 : 107.75 MB/s
bench7 / 16.04 / Jewel / kernel 4.2 : 101.54 MB/s
bench5 / 14.04 / Infernalis / kernel 4.4 : 53.61 MB/s
bench6 / 14.04 / Jewel / kernel 4.4 : 65.82 MB/s
bench7 / 16.04 / Jewel / kernel 4.4 : 61.57 MB/s
If needed, I have the raw output of "ceph tell osd.* bench"
Best regards
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