[patch 4/9] jffs2: force the jffs2 GC daemon to behave a bitbetter

[Reuben Dowle]

I have also noticed the performance degredation caused by the jffs2
garbage collection. The solution we used to this problem on our product
was to do 'pkill -STOP jffs2_gcd' very early in the boot process, then
right at the end of my boot script put 'sleep 90 && pkill -CONT
jffs2_gcd &'

This sped the boot time up a lot.

Reuben

-----Original Message-----
From: linux-mtd-bounces at lists.infradead.org
[mailto:linux-mtd-bounces at lists.infradead.org] On Behalf Of Aras Vaichas
Sent: Tuesday, 17 March 2009 12:29 p.m.
To: Ricard Wanderlof
Cc: dwmw2 at infradead.org; akpm at linux-foundation.org; dilinger at debian.org;
linux-mtd at lists.infradead.org; dilinger at queued.net
Subject: Re: [patch 4/9] jffs2: force the jffs2 GC daemon to behave a
bitbetter

Ricard Wanderlof wrote:
> On Wed, 11 Feb 2009, akpm at linux-foundation.org wrote:
>
>   
>> I've noticed some pretty poor behavior on OLPC machines after bootup,

>> when gdm/X are starting.  The GCD monopolizes the scheduler (which in

>> turns means it gets to do more nand i/o), which results in processes 
>> taking much much longer than they should to start.
>>     
>
> Can't really comment on how well the patch works, but we've also 
> noticed a similar slowdown on our systems during startup, so the idea 
> as such is welcome at any rate.
>   
I just posted a message to linux-arm-kernel regarding a similar problem
I have an at91rm9200 based machine with NAND and JFFS2.

I suspected that garbage collection was causing delays of up to 3+
seconds during which time my watchdog patting daemon was not being
scheduled ...

This was causing the watchdog timer to reset my machine but *only* when
it was under significant NAND load  i.e. boot time, loading up the main
application while GCD was running.

My solution was to double the watchdog timeout.

Aras

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