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: echo always >/sys/kernel/mm/transparent_hugepage/enabled echo 1000 > /proc/sys/vm/min_free_kbytes The setting of min_free_kbytes to 67584 leads to 716MB of memory free. Setting to 1000 leads to 20MB free. I'm afraid losing 716MB on a 4G system is way excessive regardless of THP... can't we just have a version of anti-frag that reserves a lot fewers pageblocks? Anti-frag is quite important to avoid slab to fragment everything. I don't think we can leave it like this. For now you can workaround with the above echo 1000 > ... -- 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>