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Re: very slow file deletion on an SSD

To: Joe Landman <joe.landman@xxxxxxxxx>
Subject: Re: very slow file deletion on an SSD
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Sat, 26 May 2012 21:43:22 -0500
Cc: linux-raid <linux-raid@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4FC19408.5020502@xxxxxxxxxxx>
References: <4FBF60D1.80104@xxxxxxxxx> <20120526231838.GR25351@dastard> <4FC16683.9060800@xxxxxxxxx> <20120527000701.GS25351@dastard> <4FC18845.6030301@xxxxxxxxx> <4FC19408.5020502@xxxxxxxxxxx>
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On 5/26/12 9:40 PM, Eric Sandeen wrote:
> On 5/26/12 8:49 PM, Joe Landman wrote:
>> On 05/26/2012 08:07 PM, Dave Chinner wrote:
>>> On Sat, May 26, 2012 at 07:25:55PM -0400, Joe Landman wrote:
>>>> [root@siFlash test]# ls -alF  | wc -l
>>>> 59
>>>> [root@siFlash test]# /usr/bin/time rm -f *
>>>> ^C0.00user 8.46system 0:09.55elapsed 88%CPU (0avgtext+0avgdata
>>>> 2384maxresident)k
>>>> 25352inputs+0outputs (0major+179minor)pagefaults 0swaps
>>>
>>> It's burning an awful lot of CPU time during this remove.
>>>
>>>> [root@siFlash test]# ls -alF  | wc -l
>>>> 48
>>>
>>> So, 48 files were removed, it was basically CPU bound and one took
>>> 2.6 seconds.
>>>
>>> So, how big are the files, and does the one that took 2.6s have tens
>>> of thousands of extents ('xfs_bmap -vp *' will dump the extent maps
>>> for all the files)?
>>
>> Getting some sort of out of memory error with bmap
>>
>> [root@siFlash test]# ls -alF
>> total 50466476
>> drwxr-xr-x 2 root root       4096 May 26 21:40 ./
>> drwxr-xr-x 3 root root         17 May 26 19:32 ../
>> -rw------- 1 root root 1073741824 May 26 19:36 2.r.49.0
> ...
> 
> <snip>
> 
>> [root@siFlash test]# ls -alF > x
>>
>> [root@siFlash test]# xfs_bmap -vp x
>> x:
>>  EXT: FILE-OFFSET      BLOCK-RANGE          AG AG-OFFSET          TOTAL FLAGS
>>    0: [0..7]:          212681896..212681903  2 (7555752..7555759)     8 01111
>>
>> [root@siFlash test]# xfs_bmap -vp 2.r.96.0
>> xfs_bmap: xfsctl(XFS_IOC_GETBMAPX) iflags=0x4 ["2.r.96.0"]: Cannot allocate 
>> memory
> 
> Try filefrag -v maybe, if your e2fsprogs is new enough.
> 
> Trying to remember, ENOMEM in bmap rings a bell... but this is possibly 
> indicative of an extremely fragmented file.

Ah.

f074211f xfs: fallback to vmalloc for large buffers in xfs_getbmap

fixed it in 3.4

-Eric

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