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Re: very slow file deletion on an SSD

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: very slow file deletion on an SSD
From: joe.landman@xxxxxxxxx
Date: Sat, 26 May 2012 20:10:45 -0400
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, linux-raid <linux-raid@xxxxxxxxxxxxxxx>
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In-reply-to: <20120527000701.GS25351@dastard>
References: <4FBF60D1.80104@xxxxxxxxx> <20120526231838.GR25351@dastard> <4FC16683.9060800@xxxxxxxxx> <20120527000701.GS25351@dastard>
Ok.  Will do in a few hours

Sent from my iPad

On May 26, 2012, at 8:07 PM, Dave Chinner <david@xxxxxxxxxxxxx> 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)?
> 
> if not, can you use perf top to get an ida of the CPU usage profile
> duing the rm by doing:
> 
> # perf record rm -f *
> .....
> 
> and capturing the profile via:
> 
> # perf report > profile.txt
> 
> And attaching te profile.txt file so we can see where all the CPU
> time is being spent? You can find perf in your kernel source tree
> under the tools subdir....
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@xxxxxxxxxxxxx

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