On 11/24/2015 09:29 AM, Joonsoo Kim wrote: > On Tue, Nov 24, 2015 at 03:27:43PM +0800, Aaron Lu wrote: > > Thanks. > > Okay. Output proves the theory. pagetypeinfo shows that there are > too many unmovable pageblocks. isolate_freepages() should skip these > so it's not easy to meet proper pageblock until need_resched(). Hence, > updating cached pfn doesn't happen. (You can see unchanged free_pfn > with 'grep compaction_begin tracepoint-output') Hm to me it seems that the scanners meet a lot, so they restart at zone boundaries and that's fine. There's nothing to cache. > But, I don't think that updating cached pfn is enough to solve your problem. > More complex change would be needed, I guess. One factor is probably that THP only use async compaction and those don't result in deferred compaction, which should help here. It also means that pageblock_skip bits are not being reset except by kswapd... Oh and pageblock_pfn_to_page is done before checking the pageblock skip bits, so that's why it's prominent in the profiles. Although it was less prominent (9% vs 46% before) in the last data... was perf collected while tracing, thus generating extra noise? > Thanks. > > -- > 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/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>