On Fri, Feb 25, 2011 at 08:51:49AM +0800, Shaohua Li wrote: > On Thu, 2011-02-24 at 22:04 +0800, Andrea Arcangeli wrote: > > On Thu, Feb 24, 2011 at 04:08:47PM +0800, Shaohua Li wrote: > > > with madvise, the min_free_kbytes is still high (same as the 'always' > > > case). The result is still we have about 50M memory is reserved. you can > > > try at your machine with boot option 'mem=2G' and check the zoneinfo > > > output. > > > > yes I know. The objective of that test was exactly to know if the > > problem is higher memory footprint because of THP or only the > > anti-frag/min_free_kbytes which would still be present with the > > "madvise" setting (anti-frag is only shutdown by the "never" > > setting). If you still have the out of memory with madvise, then you > > can keep THP enabled "always" and then "echo 16384 > > > /proc/sys/vm/min_free_kbytes", it should work fine then even with THP > > always mode then, no need to disable THP (simply you won't have a good > > guarantee that anti-frag is functional so the hugepage usage will be > > reduced over time compared to the default min_free_kbytes that enables > > anti-frag fully). > > I can disable THP or set the min_free_kbytes manually in our test, but > just wonder if it's possible we can avoid the memory waste even with THP > enabled, because this will make more people enable it by default. With a lower value of min_free_kbytes, THP would give diminishing returns over time as hugepage allocation success rates start degrading over time. It might not happen for several days or weeks making it a tricky problem to diagnose. So yes, the memory waste with THP enabled can be fixed but it would only be suitable for short-term benchmarks. > If you > don't consider this is a problem, we can disable THP. > -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>