Dear Andrew, >>> Check /proc/slabinfo, see if all your lowmem got eaten up by buffer_heads. >> Please see below ... > ... Was this dump taken when the system was at or near oom? No, that was a "quiescent" machine. Please see a just-before-OOM dump in my next message (in a little while). > Please send a copy of the oom-killer kernel message dump, if you still > have one. Please see one in next message, or in http://bugs.debian.org/695182 >> I tried setting dirty_ratio to "funny" values, that did not seem to >> help. > Did you try setting it as low as possible? Probably. Maybe. Sorry, cannot say with certainty. >> Did you notice my patch about bdi_position_ratio(), how it was >> plain wrong half the time (for negative x)? > Nope, please resend. Quoting from http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=101;att=1;bug=695182 : ... - In bdi_position_ratio() get difference (setpoint-dirty) right even when it is negative, which happens often. Normally these numbers are "small" and even with left-shift I never observed a 32-bit overflow. I believe it should be possible to re-write the whole function in 32-bit ints; maybe it is not worth the effort to make it "efficient"; seeing how this function was always wrong and we survived, it should simply be removed. ... --- mm/page-writeback.c.old 2012-10-17 13:50:15.000000000 +1100 +++ mm/page-writeback.c 2013-01-06 21:54:59.000000000 +1100 [ Line numbers out because other patches not shown ] ... @@ -559,7 +578,7 @@ static unsigned long bdi_position_ratio( * => fast response on large errors; small oscillation near setpoint */ setpoint = (freerun + limit) / 2; - x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, + x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, limit - setpoint + 1); pos_ratio = x; pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; ... Cheers, Paul Paul Szabo psz@xxxxxxxxxxxxxxxxx http://www.maths.usyd.edu.au/u/psz/ School of Mathematics and Statistics University of Sydney Australia -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>