On Fri, 11 Nov 2011 10:01:56 +0000 Mel Gorman <mgorman@xxxxxxx> wrote: > On Thu, Nov 10, 2011 at 03:12:11PM -0800, Andrew Morton wrote: > > On Thu, 10 Nov 2011 16:13:31 +0000 > > Mel Gorman <mgorman@xxxxxxx> wrote: > > > > > This patch once again prevents sync migration for transparent > > > hugepage allocations as it is preferable to fail a THP allocation > > > than stall. > > > > Who said? ;) > > Everyone who ever complained about stalls due to writing to USB :) oh, here it is. Who broke mesage threading? > In the last few releases, we have squashed a number of stalls due > to writing pages from the end of the LRU but sync compaction is a > relatively recent new root cause of stalls. > > > Presumably some people would prefer to get lots of > > huge pages for their 1000-hour compute job, and waiting a bit to get > > those pages is acceptable. > > > > A 1000-hour compute job will have its pages collapsed into hugepages by > khugepaged so they might not have the huge pages at the very beginning > but they get them. With khugepaged in place, there should be no need for > an additional tuneable. OK... > > Do we have the accounting in place for us to be able to determine how > > many huge page allocation attempts failed due to this change? > > > > thp_fault_fallback is the big one. It is incremented if we fail to > allocate a hugepage during fault in either > do_huge_pmd_anonymous_page or do_huge_pmd_wp_page_fallback > > thp_collapse_alloc_failed is also very interesting. It is incremented > if khugepaged tried to collapse pages into a hugepage and > failed the allocation > > The user has the option of monitoring their compute jobs hugepage > usage by reading /proc/PID/smaps and looking at the AnonHugePages > count for the large mappings of interest. Fair enough. One slight problem though: akpm:/usr/src/25> grep -r thp_collapse_alloc_failed Documentation akpm:/usr/src/25> -- 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>