From: Marc MERLIN <marc@merlins.org>
To: Martin Steigerwald <Martin@lichtvoll.de>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: How can btrfs take 23sec to stat 23K files from an SSD?
Date: Thu, 26 Jul 2012 21:40:54 -0700 [thread overview]
Message-ID: <20120727044054.GA22340@merlins.org> (raw)
In-Reply-To: <201207240956.26495.Martin@lichtvoll.de>
On Tue, Jul 24, 2012 at 09:56:26AM +0200, Martin Steigerwald wrote:
> find is fast, du is much slower:
>
> merkaba:~> echo 3 > /proc/sys/vm/drop_caches ; time ( find /usr | wc -l )
> 404166
> ( find /usr | wc -l; ) 0,03s user 0,07s system 1% cpu 9,212 total
> merkaba:~> echo 3 > /proc/sys/vm/drop_caches ; time ( du -sh /usr )
> 11G /usr
> ( du -sh /usr; ) 1,00s user 19,07s system 41% cpu 48,886 total
You're right.
gandalfthegreat [mc]# time du -sh src
514M src
real 0m25.159s
gandalfthegreat [mc]# reset_cache
gandalfthegreat [mc]# time bash -c "find src | wc -l"
15261
real 0m7.614s
But find is still slower the du on my spinning disk for the same tree.
> Anyway thats still much faster than your measurements.
Right. Your numbers look reasonable for an SSD.
Since then, I did some more tests and I'm also getting slower than normal
speeds with ext4, an indications that it's a problem with the block layer.
I'm working with some folks try to pin down the core problem, but it looks
like it's not an easy one.
Thanks for your data.
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
next prev parent reply other threads:[~2012-07-27 4:40 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 0:37 brtfs on top of dmcrypt with SSD. No corruption iff write cache off? Marc MERLIN
2012-02-01 17:56 ` Chris Mason
2012-02-02 3:23 ` Marc MERLIN
2012-02-02 12:42 ` Chris Mason
[not found] ` <20120202152722.GI12429@merlins.org>
2012-02-12 22:32 ` Marc MERLIN
2012-02-12 23:47 ` Milan Broz
2012-02-13 0:14 ` Marc MERLIN
2012-02-15 15:42 ` Calvin Walton
2012-02-15 16:55 ` Marc MERLIN
2012-02-15 16:59 ` Hugo Mills
2012-02-22 10:28 ` Justin Ossevoort
2012-02-22 11:07 ` Hugo Mills
2012-02-16 6:33 ` Chris Samuel
2012-02-18 12:33 ` Martin Steigerwald
2012-02-18 12:39 ` Martin Steigerwald
2012-02-18 12:49 ` Martin Steigerwald
2012-07-18 18:13 ` brtfs on top of dmcrypt with SSD -> Trim or no Trim Marc MERLIN
2012-07-18 20:04 ` Fajar A. Nugraha
2012-07-18 20:37 ` Marc MERLIN
2012-07-18 21:34 ` Clemens Eisserer
2012-07-18 21:48 ` Marc MERLIN
2012-07-18 21:49 ` Martin Steigerwald
2012-07-18 22:04 ` Marc MERLIN
2012-07-19 10:40 ` Martin Steigerwald
2012-07-22 18:58 ` brtfs on top of dmcrypt with SSD -> ssd or nossd + crypt performance? Marc MERLIN
2012-07-22 19:35 ` Martin Steigerwald
2012-07-22 19:43 ` Martin Steigerwald
2012-07-22 20:44 ` Marc MERLIN
2012-07-22 22:41 ` brtfs on top of dmcrypt with SSD -> file access 5x slower than spinning disk Marc MERLIN
2012-07-23 6:42 ` How can btrfs take 23sec to stat 23K files from an SSD? Marc MERLIN
2012-07-24 7:56 ` Martin Steigerwald
2012-07-27 4:40 ` Marc MERLIN [this message]
2012-07-27 11:08 ` Chris Mason
2012-07-27 18:42 ` Marc MERLIN
[not found] ` <20120801053042.GG12695@merlins.org>
2012-08-01 6:01 ` Marc MERLIN
2012-08-01 6:08 ` Fajar A. Nugraha
2012-08-01 6:21 ` Marc MERLIN
2012-08-01 21:57 ` Martin Steigerwald
2012-08-02 5:07 ` Marc MERLIN
2012-08-02 11:18 ` Martin Steigerwald
2012-08-02 17:39 ` Marc MERLIN
2012-08-02 20:20 ` Martin Steigerwald
2012-08-02 20:44 ` Marc MERLIN
2012-08-02 21:21 ` Martin Steigerwald
2012-08-02 21:49 ` Marc MERLIN
2012-08-03 18:45 ` Martin Steigerwald
2012-08-16 7:45 ` Marc MERLIN
2012-08-02 11:25 ` Martin Steigerwald
2012-08-01 6:36 ` Chris Samuel
2012-08-01 6:40 ` Marc MERLIN
2012-02-18 16:07 ` brtfs on top of dmcrypt with SSD. No corruption iff write cache off? Marc MERLIN
2012-02-19 0:53 ` Clemens Eisserer
-- strict thread matches above, loose matches on Subject: below --
2012-07-24 6:18 How can btrfs take 23sec to stat 23K files from an SSD? Marc MERLIN
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