JFFS2 is broken

Frederic Giasson fgiasson at mediatrix.com
Mon Aug 13 14:34:09 EDT 2001

Hi again Vipin,

I ran your JitterTest program on my MPC860T 50MHz embedded platform.  I
experienced worst case around 40 seconds like you did.  I think that such
jitter time is unacceptable in a real time embedded system like mine, so I
wonder what can be done to patch JFFS2 so it relinquish the CPU from time to
time... I spinkled a lot of loops into JFFS2 compression files with "if(
current->need_resched) schedule();" and the worst case was 4 seconds. 

After having spinkled the code with schedule(), I ran another application
which accessses JFFS2 too at the same time that JitterTest, and the
execution of my program took 17% more time, which in my opinion is
acceptable because now JFFS2 has to cope with 2 applications accessing it at
the same time. 

Do you think that something sharp and clean could be done with JFFS2 to fix
that problem once and for all? 


Frédéric Giasson

-----Original Message-----
From: Vipin Malik [mailto:vipin at embeddedlinuxworks.com]
Sent: Friday, August 10, 2001 10:47 PM
To: Frederic Giasson
Subject: RE: JFFS2 is broken

At 08:31 AM 8/10/2001 -0400, Frederic Giasson wrote:
>Hi Vipin,
>I'd be interested in having your testcase programs.  It would be much
>appreciated if you send me the sources.

Hi Frederic,

I've released the code under GPL and sent the entire CVS tree for the 
jitter test program to David to put under the MTD tree.

He should have that done (hopefully) sometime this weekend or by Monday.

Let me know if it's not there by monday and I'll send you a private copy.


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