On Tue, Mar 29, 2011 at 6:53 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > [cc xfs and mm lists] > > On Mon, Mar 28, 2011 at 08:39:29PM +0400, John Lepikhin wrote: >> Hello, >> >> I use high-loaded machine with 10M+ inodes inside XFS, 50+ GB of >> memory, intensive HDD traffic and 20..50 forks per second. Vanilla >> kernel 2.6.37.4. The problem is that kernel frees memory very >> aggressively. >> >> For example: >> >> 25% of memory is used by processes >> 50% for page caches >> 7% for slabs, etc. >> 18% free. >> >> That's bad but works. After few hours: >> >> 25% of memory is used by processes >> 62% for page caches >> 7% for slabs, etc. >> 5% free. >> >> Most of files are cached, works perfectly. This is the moment when >> kernel decides to free some memory. After memory reclaim: >> >> 25% of memory is used by processes >> 25% for page caches(!) >> 7% for slabs, etc. >> 43% free(!) >> >> Page cache is dropped, server becomes too slow. This is the beginning >> of new cycle. >> >> I didn't found any huge mallocs at that moment. Looks like because of >> large number of small mallocs (forks) kernel have pessimistic forecast >> about future memory usage and frees too much memory. Is there any >> options of tuning this? Any other variants? > > First it would be useful to determine why the VM is reclaiming so > much memory. If it is somewhat predictable when the excessive > reclaim is going to happen, it might be worth capturing an event > trace from the VM so we can see more precisely what it is doiing > during this event. In that case, recording the kmem/* and vmscan/* > events is probably sufficient to tell us what memory allocations > triggered reclaim and how much reclaim was done on each event. > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx > Recently, We had a similar issue. http://www.spinics.net/lists/linux-mm/msg12243.html But it seems to not merge. I don't know why since I didn't follow up the thread. Maybe Cced guys can help you. Is it a sudden big cache drop at the moment or accumulated small cache drop for long time? What's your zones' size? Please attach the result of cat /proc/zoneinfo for others. -- 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>