Am 24.06.2015 um 19:53 schrieb Ilya Dryomov:
On Wed, Jun 24, 2015 at 8:38 PM, Stefan Priebe <s.priebe@xxxxxxxxxxxx> wrote:
Am 24.06.2015 um 16:55 schrieb Nick Fisk:
That kernel probably has the bug where tcp_nodelay is not enabled. That
is fixed in Kernel 4.0+, however also in 4.0 blk-mq was introduced which
brings two other limitations:-
blk-mq is terrible slow. That's correct.
Is that a general sentiment or your experience with rbd? If the
latter, can you describe your workload and provide some before and
after blk-mq numbers? We'd be very interested in identifying and
fixing any performance regressions you might have on blk-mq rbd.
oh i'm sorry. I accidently compiled blk-mq into the kernel when 3.18.1
came out and i was wondering why my I/O waits on my ceph osds where
doubled or even tripled. After reverting back to cfq everything was fine
again. I didn't digged deeper into it as i thought blk-mq is
experimental in 3.18.
If you're willing to assist i can give it a try - but need the patches
you mention first (git commit ids?).
Greets,
Stefan
(As I mentioned in another reply, the two limitations Nick brought up
are fixed - the patches are on their way to mainline and are simple
enough for you to apply or I can build a kernel with those patches
applied for you so you can test.)
Thanks,
Ilya
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