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Re: JFFS2: powerfailtesting again



Hi David
Sorry for some period of silence, I've encountered several problems in my setup
( sysrq wasn't working on my console - patched, Expect sometimes looses data ->
simulated jffs2 failures - make workaround , several time-consuming runs to
verify changes). But now I'm ready to supply You with more reliable data.

JFFS2 looks stable after ~ 300 reboots (and keeps running) --- VERY GOOD !!!

I've made debug printout when GC pass starts and stops and made timing of this,
as well as overall boot , init and copy stages timing. It appears that mean
time of this stages in a long run are 2, 117 and 182 seconds while on freshly
flashed filesytem it takes 2, 2 and 14 seconds respectively. The mean time of
GC mass is about 9 seconds but there is huge variation in it, i've seen ones
longer than 3 min.. As You can remember GC demon is supposed to be low priority
process but it implemented as kernel thread and thus cannot be interrupted by
timer.

IMHO 3 min of uninterrupted running is a way long. This definitely looks like a
hangover. Is it possible to make calls to schedule() more frequent, not just
between GC passes ?

Did anybody perform profiling of JFFS , where is a bottleneck ? 10 minute for
boot from 3mb partition is a rather long time.
Do You have plans to improve performance ? Is there room for this ?

Thank You in advance
With best regards,
                        Vladimir.


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