Re: [PATCH 0/2] patches to improve cluster raid1 performance [V2]

[Dongmao Zhang <dmzhang@suse.com>]

great, thanks for your response:)


于 2013年09月27日 01:17, Brassow Jonathan 写道:
> I'll try to look these patches over during the next couple days.  Thanks for sending.
>
> One thing I'll be looking for is that any delays in the flush don't violate the need for dm-raid1.c to ensure that the log changes have hit the disk before performing any writes.
>
>   brassow
>
> On Sep 26, 2013, at 5:50 AM, dongmao zhang wrote:
>
>> This patch change DM_ULOG_REQUEST_VERSION from 2 to 3. It could
>> tell cmirrord that kernel is now supporting delay some flushes, and
>> cmirrord will do someting accordingly.
>>
>>
>> Based on my test result, the cluster raid1 writes loss 80% performance. I found
>> that the most time is occupied by the function userspace_flush.
>>
>> Usually userspace_flush needs three stages(mark, clear, flush)to communicate with cmirrord.
>>
>>>  From the cmirrord's perspective, mark and flush functions run cluster_send first and then return to
>> the kernel.
>>
>> In other words, the requests of mark_region and flush in userspace_flush
>> at least require a cluster_send period to finish. this is the root cause
>> of bad performance.
>>
>> The idea is to merge flush and mark request together in both cmirrord and dm-log-userspace.
>>
>> We run clog_flush directly after clog_mark_region. So the userspace_flush do not
>> have to request flush again after requesting mark_region.  Moreover, I think the flush
>> of clear region could be delayed. If we have both mark and clear region, only sending
>> a mark_region request is OK, because clog_flush will automatically run.(ignore the clean_region
>> time). It only takes one cluster_send period. If we have only mark region,
>> a mark_region request is also OK, it takes one cluster_send period. If we have only
>> clear_region, we could delay the flush of cleared_region for 3 seconds.
>>
>> Overall, before the patch, mark_region require approximately two cluster_send
>> period(mark_region and flush), after the patch, mark_region only needs one
>> cluster_send period. Based on my test, the performance is as twice as before.
>>
>>
>>
>> dongmao zhang (2):
>>   improve the performance of dm-log-userspace
>>   change API of dm-log-userspace to support delay flush
>>
>> drivers/md/dm-log-userspace-base.c    |  109 ++++++++++++++++++++++++++++++---
>> include/uapi/linux/dm-log-userspace.h |    2 +-
>> 2 files changed, 101 insertions(+), 10 deletions(-)
>>
>> --
>> 1.7.3.4
>>
>> --
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>> dm-devel@redhat.com
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>
>

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