On Mon, Jan 24, 2011 at 04:00:34PM +0100, Andrea Arcangeli wrote: > eOn Mon, Jan 24, 2011 at 11:56:46AM +0800, Shaohua Li wrote: > > Hi, > > With transparent huge page, min_free_kbytes is set too big. > > Before: > > Node 0, zone DMA32 > > pages free 1812 > > min 1424 > > low 1780 > > high 2136 > > scanned 0 > > spanned 519168 > > present 511496 > > > > After: > > Node 0, zone DMA32 > > pages free 482708 > > min 11178 > > low 13972 > > high 16767 > > scanned 0 > > spanned 519168 > > present 511496 > > This caused different performance problems in our test. I wonder why we > > set the value so big. > > It's to enable Mel's anti-frag that keeps pageblocks with movable and > unmovable stuff separated, same as "hugeadm > --set-recommended-min_free_kbytes". > > Now that I checked, I'm seeing quite too much free memory with only 4G > of ram... You can see the difference with a "cp /dev/sda /dev/null" in > background interleaving these two commands: > What kernel is this and is commit [99504748: mm: kswapd: stop high-order balancing when any suitable zone is balanced] present in the kernel you are testing? I'm having very little luck reproducing your scenario with 2.6.38-rc2. min_free_kbytes is as expected and the free memory is close to expectations when copying /dev/sda to /dev/null with or without transparent hugepages. -- Mel Gorman Linux Technology Center IBM Dublin Software Lab -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>