linux-kernel - Re: High kernel CPU usage when copying files

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Date:	Fri, 24 Apr 2009 11:23:48 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Rutkov Denis <dendron2000@...l.ru>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: High kernel CPU usage when copying files

> Whenever I copy files I got very high CPU usage from kernel. I tested this with ext3, ext4 and fat32 file systems. To trace the problem I installed oprofile and debug kernel image. I ran the profiler during file copying and saw that there are many calls to copy_to_user_ll and copy_from_user_ll functions. So I have two questions:
> 
> 1. Is this normal I get so many of those function calls?

Yes

> 2. What can I do to further trace this bug?


Are you seeing high CPU usage or just a lot of D state processes (blocked
waiting I/O) ?

Alan
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