linux-kernel - Re: stat benchmark

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Date:	Thu, 24 Apr 2008 23:44:04 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Soeren Sandmann <sandmann@...mi.au.dk>
cc:	linux-kernel@...r.kernel.org
Subject: Re: stat benchmark


On Thursday 2008-04-24 22:59, Soeren Sandmann wrote:
>
>    http://www.daimi.au.dk/~sandmann/stat-benchmark.c
>
>there is a simple program that will measure the time it takes to stat
>every file in the current directory with a cold cache.
>
>This is essentially what applications do in a number of common cases
>such as "ls -l", nautilus opening a directory, or an "open file"
>dialog being showed.

Mh somewhat. Some programs/libraries unnecessarily stat No, nautilus is excluded

>
>Unfortunately, performance of that operation kinda sucks. On my system
>(ext3), it produces:
>
>    c-24-61-65-93:~% sudo ./a.out 
>    Time to readdir(): 0.307671 s
>    Time to stat 2349 files: 8.203693 s
>
>8 seconds is about 80 times slower than what a user perceives as
>"instantly" and slow enough that we really should display a progress
>bar if it can't be fixed.
>
>So I am looking for ways to improve this.
>
>Under the theory that disk seeks are killing us, one idea is to add a
>'multistat' system call that would allow statting of many files at a
>time, which would give the disk scheduler more to work with. 
>
>Possibly the same thing would need to be done for the getxattr
>information.
>
>Does this sound like a reasonable idea?
>

XFS for example already has bulkstat, but it is not really
exported to userspace :-/
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