On Mon, 2011-12-12 at 10:43 +0800, Li, Shaohua wrote: > On Wed, 2011-12-07 at 15:28 +0800, David Rientjes wrote: > > On Wed, 7 Dec 2011, Shaohua Li wrote: > > > > > interesting. I did similar experiment before (try to sort the page > > > according to free number), but it appears quite hard. The free number of > > > a page is dynamic, eg more slabs can be freed when the page is in > > > partial list. And in netperf test, the partial list could be very very > > > long. Can you post your patch, I definitely what to look at it. > > > > It was over a couple of years ago and the slub code has changed > > significantly since then, but you can see the general concept of the "slab > > thrashing" problem with netperf and my solution back then: > > > > http://marc.info/?l=linux-kernel&m=123839191416478 > > http://marc.info/?l=linux-kernel&m=123839203016592 > > http://marc.info/?l=linux-kernel&m=123839202916583 > > > > I also had a separate patchset that, instead of this approach, would just > > iterate through the partial list in get_partial_node() looking for > > anything where the number of free objects met a certain threshold, which > > still defaulted to 25% and instantly picked it. The overhead was taking > > slab_lock() for each page, but that was nullified by the performance > > speedup of using the alloc fastpath a majority of the time for both > > kmalloc-256 and kmalloc-2k when in the past it had only been able to serve > > one or two allocs. If no partial slab met the threshold, the slab_lock() > > is held of the partial slab with the most free objects and returned > > instead. > With the per-cpu partial list, I didn't see any workload which is still > suffering from the list lock, The merge error that you fixed in 3.2-rc1 for hackbench regression is due to add slub to node partial head. And data of hackbench show node partial is still heavy used in allocation. /sys/kernel/slab/kmalloc-256/alloc_fastpath:225208640 /sys/kernel/slab/kmalloc-256/alloc_from_partial:5276300 /sys/kernel/slab/kmalloc-256/alloc_from_pcp:8326041 -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>