Fwd: Re: Reiser FS performance thingy.

Fwd: Re: Reiser FS performance thingy.

[Rogier Wolff]

> OK Rogier, please search through the archive, and post the URL of your
> previous report.  That will be most helpful.

I searched my own mail archive, remembering that I got an Email
from someone named Hans. Do you know him? :-)

		Roger. 

----- Forwarded message from Hans Reiser <reiser@namesys.com> -----

From: Hans Reiser <reiser@namesys.com>
To: Rogier Wolff <R.E.Wolff@BitWizard.nl>
Date: Wed, 07 Aug 2002 00:03:00 +0400
Subject: Re: Reiser FS performance thingy.
X-Spam-Status: No, hits=-100.0 required=5.0 tests=A_FROM_IN_AUTO_WLIST version=2.01

Rogier Wolff wrote:

>Hi Hans,
>
>We've got a big filesystem on some pretty fast disks running reiserfs:
>
>Filesystem            Size  Used Avail Use% Mounted on
>/dev/md0              603G  466G  137G  78% /recover5
>
>/dev/md0 on /recover5 type reiserfs (rw)
>
>Just a couple of minutes ago, we happened to have only 60G left on
>that filesystem, and suddenly performance went down the drain. Like
>write 500k per second, while normally we're able to read (and write)
>around 100Mb per second off the disks.
>
>We know that you're not supposed to use the last 10% of a disk because
>of performance reasons, but this seems like an enormous penalty.
>
>My impression is that the "search for a free block" routine in
>reiserfs somehow uses the wrong starting point. It is customary to
>start searching where you found a free block last time and not say "at
>the ideal point if you consider the directory entry". Then you might
>end up searching 500G worth of block free flags for a spot for EVERY
>block allocated....
>
>The processes involved in writing to that partition were using LOTS of
>CPU time in system mode. Often top would tell me that over 180% of one
>CPU was spent in system mode.
>
>As you can see, we've solved the problem by doing a little cleaning,
>but you may want to look into this for the future.... 
>
>
>Thanks for the fast fsck. :-)
>
>
>		Roger. 
>
> 
>
Proper solutions from us to your problem include enhanced bitmap 
scanning code (see 2.4.20 when it comes out), and repacking (see 
Reiser4.1 when it comes out).

-- 
Hans




----- End forwarded message -----

-- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
* I didn't say it was your fault. I said I was going to blame it on you. *

Re: Fwd: Re: Reiser FS performance thingy.

[Oleg Drokin]

Hello!

On Thu, Aug 07, 2003 at 08:58:54PM +0200, Rogier Wolff wrote:
> > OK Rogier, please search through the archive, and post the URL of your
> > previous report.  That will be most helpful.
> I searched my own mail archive, remembering that I got an Email
> from someone named Hans. Do you know him? :-)

I am still interested in a metadata snapshot from the filesystem that
makes slow block allocations with 2.4.20+ kernels.
Do you still have one?
Thank you.

Bye,
    Oleg

Re: Fwd: Re: Reiser FS performance thingy.

[Rogier Wolff]

On Fri, Aug 08, 2003 at 02:00:00PM +0400, Oleg Drokin wrote:
> Hello!
> 
> On Thu, Aug 07, 2003 at 08:58:54PM +0200, Rogier Wolff wrote:
> > > OK Rogier, please search through the archive, and post the URL of your
> > > previous report.  That will be most helpful.
> > I searched my own mail archive, remembering that I got an Email
> > from someone named Hans. Do you know him? :-)
> 
> I am still interested in a metadata snapshot from the filesystem that
> makes slow block allocations with 2.4.20+ kernels.
> Do you still have one?

Here I go again: 

What part of: "We had that problem about a year ago, we were told it
had been fixed. We didn't have the chance to upgrade immediately, but
are now running 2.4.20, which may include the then-proposed fix." 
don't you understand.

Hans mailed me about that issue today one year and one day ago. I copied
that Email to the list. 

		Roger. 

-- 
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Re: Fwd: Re: Reiser FS performance thingy.

[Oleg Drokin]

Hello!

On Fri, Aug 08, 2003 at 12:31:41PM +0200, Rogier Wolff wrote:
> > > > OK Rogier, please search through the archive, and post the URL of your
> > > > previous report.  That will be most helpful.
> > > I searched my own mail archive, remembering that I got an Email
> > > from someone named Hans. Do you know him? :-)
> > I am still interested in a metadata snapshot from the filesystem that
> > makes slow block allocations with 2.4.20+ kernels.
> > Do you still have one?
> Here I go again: 
> What part of: "We had that problem about a year ago, we were told it
> had been fixed. We didn't have the chance to upgrade immediately, but
> are now running 2.4.20, which may include the then-proposed fix." 
> don't you understand.

Hm. Now when you put it this way...
Your first email was sounding like if you still experience this same
problem on 2.4.20 (first you described the problem, then
you said you use 2.4.20).

Ok, if you do not see anything wrong with 2.4.20, this is great news ;)

Bye,
    Oleg