From: Dave Chinner <david@fromorbit.com>
To: Subranshu Patel <spatel.ml@gmail.com>
Cc: xfs@oss.sgi.com
Subject: Re: High %user CPU in XFS
Date: Mon, 18 Feb 2013 08:25:36 +1100 [thread overview]
Message-ID: <20130217212536.GY26694@dastard> (raw)
In-Reply-To: <CAEUQcehy1fy5-W-TA--2emBgL3y9JskqRPCZf1ED5JDbPHqKTQ@mail.gmail.com>
On Sun, Feb 17, 2013 at 09:20:46PM +0530, Subranshu Patel wrote:
> I created 2 filesystem on my system (RHEL 6.3, kernel 2.6.32) - XFS
> and EXT4 and mounted them.
>
> On both the filesystem I executed a program which performed the following:
> - Create large number of directories
> - Removing all the directories
>
> During the execution of the program, I monitored the %user and %system
> CPU usage (using sar command)
>
> For EXT4 the %user was 1% and %system was 21%
> For XFS the %user was 20% and %system was 52%
>
> But I am not able to understand %user consumption, since %user reports
> the CPU usage of the user level (application), shouldn't it be the
> same for both EXT4 and XFS?
Perf is your friend.
> What are the factors that decide the %user component keeping in mind
> that only the filesystem is different?
Page faults, CPU cache misses. XFS has a significantly large icache
and dcache footprint than ext4, so those are the likely causes.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2013-02-17 21:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-17 15:50 High %user CPU in XFS Subranshu Patel
2013-02-17 21:04 ` Tru Huynh
2013-02-17 21:29 ` Dave Chinner
2013-02-17 21:25 ` Dave Chinner [this message]
2013-02-18 14:17 ` Subranshu Patel
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