* High %user CPU in XFS
@ 2013-02-17 15:50 Subranshu Patel
2013-02-17 21:04 ` Tru Huynh
2013-02-17 21:25 ` Dave Chinner
0 siblings, 2 replies; 5+ messages in thread
From: Subranshu Patel @ 2013-02-17 15:50 UTC (permalink / raw)
To: xfs
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?
What are the factors that decide the %user component keeping in mind
that only the filesystem is different?
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* Re: High %user CPU in XFS
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
1 sibling, 1 reply; 5+ messages in thread
From: Tru Huynh @ 2013-02-17 21:04 UTC (permalink / raw)
To: Subranshu Patel; +Cc: xfs
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.
probably:
https://bugzilla.redhat.com/show_bug.cgi?id=883905
Tru
--
Dr Tru Huynh | http://www.pasteur.fr/recherche/unites/Binfs/
mailto:tru@pasteur.fr | tel/fax +33 1 45 68 87 37/19
Institut Pasteur, 25-28 rue du Docteur Roux, 75724 Paris CEDEX 15 France
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* Re: High %user CPU in XFS
2013-02-17 15:50 High %user CPU in XFS Subranshu Patel
2013-02-17 21:04 ` Tru Huynh
@ 2013-02-17 21:25 ` Dave Chinner
2013-02-18 14:17 ` Subranshu Patel
1 sibling, 1 reply; 5+ messages in thread
From: Dave Chinner @ 2013-02-17 21:25 UTC (permalink / raw)
To: Subranshu Patel; +Cc: xfs
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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* Re: High %user CPU in XFS
2013-02-17 21:04 ` Tru Huynh
@ 2013-02-17 21:29 ` Dave Chinner
0 siblings, 0 replies; 5+ messages in thread
From: Dave Chinner @ 2013-02-17 21:29 UTC (permalink / raw)
To: Tru Huynh; +Cc: Subranshu Patel, xfs
On Sun, Feb 17, 2013 at 10:04:08PM +0100, Tru Huynh wrote:
> 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.
> probably:
> https://bugzilla.redhat.com/show_bug.cgi?id=883905
Definitely not. That's an idle condition issue and does not
increase CPU usage at all.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: High %user CPU in XFS
2013-02-17 21:25 ` Dave Chinner
@ 2013-02-18 14:17 ` Subranshu Patel
0 siblings, 0 replies; 5+ messages in thread
From: Subranshu Patel @ 2013-02-18 14:17 UTC (permalink / raw)
To: Dave Chinner; +Cc: xfs
> Page faults, CPU cache misses. XFS has a significantly large icache
> and dcache footprint than ext4, so those are the likely causes
I have a query. Will page fault, cache misses etc will increase the
%user CPU utilization or %system CPU utilization. I thought it will
affect the %system and not %user CPU usage?
%user - Percentage of CPU utilization that occurred while executing at
the user level (application).
%system - Percentage of CPU utilization that occurred while executing
at the system level (kernel).
On Mon, Feb 18, 2013 at 2:55 AM, Dave Chinner <david@fromorbit.com> wrote:
> 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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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
2013-02-18 14:17 ` Subranshu Patel
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