linux-kernel - Re: ext2/3/4 performance issue

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Message-ID: <20150510215607.GA14298@thunk.org>
Date:	Sun, 10 May 2015 17:56:07 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Bernhard Kraft <kraftb@...nk-open.at>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: ext2/3/4 performance issue

On Sun, May 10, 2015 at 10:01:09AM +0200, Bernhard Kraft wrote:
> 
> I work on implementing the ext2 filesystem for a PIC microcontroller and
> while reading the sources of it in the linux kernel I stumbled upon the
> following performance issue.....

Your observations are currect as far as ext2 is concerned; by the time
you get to ext4, it's a bit more complicated.  Also, the
extN_bg_has_super() has in general not been a bottleneck, at least on
modern CPUs.  Perhaps it would be more of an issue on a PIC
microcontroller, of course.

Finally, note that the overhead is cached so it is only calculated the
first time the extN_statfs() is called.

Cheers,

					- Ted
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