[mythtv-users] Howto prevent MythTV flushing/Syncing disk writes (LiveTV/Recordings)

Tony Lill ajlill at ajlc.waterloo.on.ca
Wed Mar 19 16:50:58 UTC 2008


If your disk writes are making other stuff choppy or pause, there are
some kernel tuning stuff that can help.

# % of physical memory after which a process doing a write will be paused
# untill dirty pages have been written
# default 40
echo 50 > /proc/sys/vm/dirty_ratio

# % of physical memory at which pdflush will be woken. Hopefull this will limit
# system pauses for flushes
# default 10
echo 5 > /proc/sys/vm/dirty_background_ratio

You need to tweak these based on how much memory your system has. The
more memory, the lower dirty_background_ratio needs to be. 5 works for
me with 1G and recording 2 standard def mpeg2 streams. Basicly, what
this does is makes pdflush wake up more often so there's less data to
write in one shot.

Also, make sure you are using a newer kernel (at least 2.6.23). I've
been dealing with performance problems ever since I "upgraded" from
the 2.4 series, and .23 is the first one that didn't have problems
sharing resources between processes.

--
Tony Lill,                         Tony.Lill at AJLC.Waterloo.ON.CA
President, A. J. Lill Consultants        fax/data (519) 650 3571
539 Grand Valley Dr., Cambridge, Ont. N3H 2S2     (519) 241 2461
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