Re: Is XFS suitable for 350 million files on 20TB storage?

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Thanks,

upgraded to 3.16.2 and xfsprogs 3.2.1. Let's see how it behaves with finobt.

Greets,
Stefan


Am 07.09.2014 um 00:56 schrieb Dave Chinner:
> On Sat, Sep 06, 2014 at 11:04:13AM -0400, Brian Foster wrote:
>> On Sat, Sep 06, 2014 at 09:35:15AM +0200, Stefan Priebe wrote:
>>> Hi Dave,
>>>
>>> Am 06.09.2014 01:05, schrieb Dave Chinner:
>>>> On Fri, Sep 05, 2014 at 02:40:32PM +0200, Stefan Priebe - Profihost AG wrote:
>>>>>
>>>>> Am 05.09.2014 um 14:30 schrieb Brian Foster:
>>>>>> On Fri, Sep 05, 2014 at 11:47:29AM +0200, Stefan Priebe - Profihost AG wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> i have a backup system running 20TB of storage having 350 million files.
>>>>>>> This was working fine for month.
>>>>>>>
>>>>>>> But now the free space is so heavily fragmented that i only see the
>>>>>>> kworker with 4x 100% CPU and write speed beeing very slow. 15TB of the
>>>>>>> 20TB are in use.
>>>>
>>>> What does perf tell you about the CPU being burnt? (i.e run perf top
>>>> for 10-20s while that CPU burn is happening and paste the top 10 CPU
>>>> consuming functions).
>>>
>>> here we go:
>>>  15,79%  [kernel]            [k] xfs_inobt_get_rec
>>>  14,57%  [kernel]            [k] xfs_btree_get_rec
>>>  10,37%  [kernel]            [k] xfs_btree_increment
>>>   7,20%  [kernel]            [k] xfs_btree_get_block
>>>   6,13%  [kernel]            [k] xfs_btree_rec_offset
>>>   4,90%  [kernel]            [k] xfs_dialloc_ag
>>>   3,53%  [kernel]            [k] xfs_btree_readahead
>>>   2,87%  [kernel]            [k] xfs_btree_rec_addr
>>>   2,80%  [kernel]            [k] _xfs_buf_find
>>>   1,94%  [kernel]            [k] intel_idle
>>>   1,49%  [kernel]            [k] _raw_spin_lock
>>>   1,13%  [kernel]            [k] copy_pte_range
>>>   1,10%  [kernel]            [k] unmap_single_vma
>>>
>>
>> The top 6 or so items look related to inode allocation, so that probably
>> confirms the primary bottleneck as searching around for free inodes out
>> of the existing inode chunks, precisely what the finobt is intended to
>> resolve. That was introduced in 3.16 kernels, so unfortunately it is not
>> available in 3.10.
> 
> *nod*
> 
> Again, the only workaround for this on a non-finobt fs is to greatly
> increase the number of AGs so there's less records in each btree to
> search.
> 
> Cheers,
> 
> Dave.
> 

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