Nate Diller wrote:
just found the culprit. guess i should have read the code the first
time. get_dirty_limits() in drivers/block/page_writeback.c has a
hard-coded upper limit to dirty_ratio. it's capped to half of the
unmapped pages, so maybe 30-40% of your system's memory. so if you are
brave, just remove the "/ 2" parts from the 'if (dirty_ratio >
unmapped_ratio / 2) dirty_ratio = unmapped_ratio / 2;' check, and you
can have all the OOM goodness you want.
Well well well.
Thank you Nate!
I changed that bit of code to:
if (dirty_ratio > unmapped_ratio - 10)
dirty_ratio = unmapped_ratio - 10;
and added a couple of sanity checks so that it couldn't get below 5 or above 95.
Then set /proc/sys/vm/dirty_ratio to 95 and dirty_background_ratio to 1.
Guess what? Now my video streams for 120 seconds before being throttled. This is *much better*.
It's now quite feasible to reach 30 seconds by finding a faster disk and/or adding another 512M
or RAM.
I guess the hard-coded limit is in there for a reason, but I sure wish it was adjustable without
this sort of hacking.
regards, Anthony
--
Anthony Wesley
Director and IT/Network Consultant
Smart Networks Pty Ltd
Acquerra Pty Ltd
[email protected]
Phone: (02) 62595404 or 0419409836
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