On 2.9.2015 10:55, Konstantin Khlebnikov wrote: > On Wed, Sep 2, 2015 at 1:26 AM, David Rientjes <rientjes@xxxxxxxxxx> wrote: >> On Tue, 25 Aug 2015, Vlastimil Babka wrote: >> >>>> THP works very well when system has a lot of free memory. >>>> Probably default should be weakened to "only if we have tons of free >>>> memory". >>>> For example allocate THP pages atomically, only if buddy allocator already >>>> has huge pages. Also them could be pre-zeroed in background. >>> >>> I've been proposing series that try to move more THP allocation activity from >>> the page faults into khugepaged, but no success yet. >>> >>> Maybe we should just start with changing the default of >>> /sys/kernel/mm/transparent_hugepage/defrag to "madvise". >> >> I would need to revert this internally to avoid performance degradation, I >> believe others would report the same. > > What about adding new mode "guess" -- something between always and madvise? > > In this mode kernel tries to avoid performance impact for non-madvised vmas and > allocates 0-order pages if hugepages are not available right now. > (for example do allocations with GFP_NOWAIT) That's exactly what happens when /sys/kernel/mm/transparent_hugepage/defrag is set to "madvise". > I think we'll get all benefits without losing performance. -- 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>