Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1204167
| From | Rafal Mielniczuk <rafal.mielniczuk@citrix.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback |
| Date | 2015-08-10 13:10 +0200 |
| Message-ID | <pVT7Q-4oP-33@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <pk8hB-6dq-35@gated-at.bofh.it> <pk8rg-6ps-15@gated-at.bofh.it> <ppCeZ-5yZ-9@gated-at.bofh.it> <pH4HV-4vT-33@gated-at.bofh.it> <pHgzn-5wf-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 01/07/15 04:03, Jens Axboe wrote:
> On 06/30/2015 08:21 AM, Marcus Granado wrote:
>> Hi,
>>
>> Our measurements for the multiqueue patch indicate a clear improvement
>> in iops when more queues are used.
>>
>> The measurements were obtained under the following conditions:
>>
>> - using blkback as the dom0 backend with the multiqueue patch applied to
>> a dom0 kernel 4.0 on 8 vcpus.
>>
>> - using a recent Ubuntu 15.04 kernel 3.19 with multiqueue frontend
>> applied to be used as a guest on 4 vcpus
>>
>> - using a micron RealSSD P320h as the underlying local storage on a Dell
>> PowerEdge R720 with 2 Xeon E5-2643 v2 cpus.
>>
>> - fio 2.2.7-22-g36870 as the generator of synthetic loads in the guest.
>> We used direct_io to skip caching in the guest and ran fio for 60s
>> reading a number of block sizes ranging from 512 bytes to 4MiB. Queue
>> depth of 32 for each queue was used to saturate individual vcpus in the
>> guest.
>>
>> We were interested in observing storage iops for different values of
>> block sizes. Our expectation was that iops would improve when increasing
>> the number of queues, because both the guest and dom0 would be able to
>> make use of more vcpus to handle these requests.
>>
>> These are the results (as aggregate iops for all the fio threads) that
>> we got for the conditions above with sequential reads:
>>
>> fio_threads io_depth block_size 1-queue_iops 8-queue_iops
>> 8 32 512 158K 264K
>> 8 32 1K 157K 260K
>> 8 32 2K 157K 258K
>> 8 32 4K 148K 257K
>> 8 32 8K 124K 207K
>> 8 32 16K 84K 105K
>> 8 32 32K 50K 54K
>> 8 32 64K 24K 27K
>> 8 32 128K 11K 13K
>>
>> 8-queue iops was better than single queue iops for all the block sizes.
>> There were very good improvements as well for sequential writes with
>> block size 4K (from 80K iops with single queue to 230K iops with 8
>> queues), and no regressions were visible in any measurement performed.
> Great results! And I don't know why this code has lingered for so long,
> so thanks for helping get some attention to this again.
>
> Personally I'd be really interested in the results for the same set of
> tests, but without the blk-mq patches. Do you have them, or could you
> potentially run them?
>
Hello,
We rerun the tests for sequential reads with the identical settings but with Bob Liu's multiqueue patches reverted from dom0 and guest kernels.
The results we obtained were *better* than the results we got with multiqueue patches applied:
fio_threads io_depth block_size 1-queue_iops 8-queue_iops *no-mq-patches_iops*
8 32 512 158K 264K 321K
8 32 1K 157K 260K 328K
8 32 2K 157K 258K 336K
8 32 4K 148K 257K 308K
8 32 8K 124K 207K 188K
8 32 16K 84K 105K 82K
8 32 32K 50K 54K 36K
8 32 64K 24K 27K 16K
8 32 128K 11K 13K 11K
We noticed that the requests are not merged by the guest when the multiqueue patches are applied,
which results in a regression for small block sizes (RealSSD P320h's optimal block size is around 32-64KB).
We observed similar regression for the Dell MZ-5EA1000-0D3 100 GB 2.5" Internal SSD
As I understand blk-mq layer bypasses I/O scheduler which also effectively disables merges.
Could you explain why it is difficult to enable merging in the blk-mq layer?
That could help closing the performance gap we observed.
Otherwise, the tests shows that the multiqueue patches does not improve the performance,
at least when it comes to sequential read/writes operations.
Rafal
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Rafal Mielniczuk <rafal.mielniczuk@citrix.com> - 2015-08-10 13:10 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Bob Liu <bob.liu@oracle.com> - 2015-08-10 13:20 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Jens Axboe <axboe@fb.com> - 2015-08-10 18:00 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Bob Liu <bob.liu@oracle.com> - 2015-08-11 08:10 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Rafal Mielniczuk <rafal.mielniczuk@citrix.com> - 2015-08-11 11:50 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Jens Axboe <axboe@fb.com> - 2015-08-11 19:40 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Bob Liu <bob.liu@oracle.com> - 2015-08-12 12:20 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Rafal Mielniczuk <rafal.mielniczuk@citrix.com> - 2015-08-12 19:20 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Bob Liu <bob.liu@oracle.com> - 2015-08-14 10:40 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Rafal Mielniczuk <rafal.mielniczuk@citrix.com> - 2015-08-14 14:40 +0200
Re: [Xen-devel] [PATCH RFC v2 0/5] Multi-queue support for xen-blkfront and xen-blkback Rafal Mielniczuk <rafal.mielniczuk@citrix.com> - 2015-08-18 11:50 +0200
csiph-web