hi,llya
2015-08-26 23:56 GMT+08:00 Ilya Dryomov <[email protected]>:
> On Wed, Aug 26, 2015 at 6:22 PM, Haomai Wang <[email protected]> wrote:
>> On Wed, Aug 26, 2015 at 11:16 PM, huang jun <[email protected]> wrote:
>>> hi,all
>>> we create a 2TB rbd image, after map it to local,
>>> then we format it to xfs with 'mkfs.xfs /dev/rbd0', it spent 318
>>> seconds to finish, but local physical disk with the same size just
>>> need 6 seconds.
>>>
>>
>> I think librbd have two PR related to this.
>>
>>> After debug, we found there are two steps in rbd module during formating:
>>> a) send 233093 DELETE requests to osds(number_of_requests = 2TB / 4MB),
>>> this step spent almost 92 seconds.
>>
>> I guess this(https://github.com/ceph/ceph/pull/4221/files) may help
>
> It's submitting deletes for non-existent objects, not zeroing. The
> only thing that will really help here is the addition of rbd object map
> support to the kernel client. That could happen in 4.4, but 4.5 is
> a safer bet.
>
>>
>>> b) send 4238 messages like this: [set-alloc-hint object_size 4194304
>>> write_size 4194304,write 0~512] to osds, that spent 227 seconds.
>>
>> I think kernel rbd also need to use
>> https://github.com/ceph/ceph/pull/4983/files
>
> set-alloc-hint may be a problem, but I think a bigger problem is the
> size of the write. Are all those writes 512 bytes long?
>
In another test to format 2TB rbd device,
there are :
2 messages,each write 131072 bytes
4000 messages, each write 262144 bytes
112 messages, each write 4096 bytes
194 messages, each write 512 bytes
the xfs info:
meta-data = /dev/rbd/rbd/test2t isize=256 agcount=33, agsize=16382976 blks
= sectsz=512 attr=2,
projid32bit=1
= crc=0
data = bsize=4096
blocks=524288000, imaxpct=5
= sunit=1024 swidth=1024 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=256000, version=2
= sectsz=512 sunit=8
blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
> Thanks,
>
> Ilya
--
thanks
huangjun
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