Subject: Re: [KORG] Re: kernel.org lies about latest -mm kernel
From: "J.H." <warthog9@kernel.org>
To: Matti Aarnio <matti.aarnio@zmailer.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>, Andrew Morton <akpm@osdl.org>,
       Pavel Machek <pavel@ucw.cz>, kernel list <linux-kernel@vger.kernel.org>,
       hpa@zytor.com, webmaster@kernel.org
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Date: Sun, 17 Dec 2006 16:42:56 -0800
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On Mon, 2006-12-18 at 00:37 +0200, Matti Aarnio wrote:
> On Sun, Dec 17, 2006 at 10:23:54AM -0800, Randy Dunlap wrote:
> > J.H. wrote:
> ...
> > >The root cause boils down to with git, gitweb and the normal mirroring
> > >on the frontend machines our basic working set no longer stays resident
> > >in memory, which is forcing more and more to actively go to disk causing
> > >a much higher I/O load.  You have the added problem that one of the
> > >frontend machines is getting hit harder than the other due to several
> > >factors: various DNS servers not round robining, people explicitly
> > >hitting [git|mirrors|www|etc]1 instead of 2 for whatever reason and
> > >probably several other factors we aren't aware of.  This has caused the
> > >average load on that machine to hover around 150-200 and if for whatever
> > >reason we have to take one of the machines down the load on the
> > >remaining machine will skyrocket to 2000+.  
> 
> Relaying on DNS and clients doing round-robin load-balancing is doomed.
> 
> You really, REALLY, need external L4 load-balancer switches.
> (And installation help from somebody who really knows how to do this
> kind of services on a cluster.)

While this is a really good idea when you have systems that are all in a
single location, with a single uplink and what not - this isn't the case
with kernel.org.  Our machines are currently in three separate
facilities in the US (spanning two different states), with us working on
a fourth in Europe.

> > >Since it's apparent not everyone is aware of what we are doing, I'll
> > >mention briefly some of the bigger points.
> ...
> > >- We've cut back on the number of ftp and rsync users to the machines.
> > >Basically we are cutting back where we can in an attempt to keep the
> > >load from spiraling out of control, this helped a bit when we recently
> > >had to take one of the machines down and instead of loads spiking into
> > >the 2000+ range we peaked at about 500-600 I believe.
> 
> How about having filesystems mounted with "noatime" ?
> Or do you already do that ?

We've been doing that for over a year.

- John

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