On Tue, Nov 15, 2011 at 03:00:09AM +0100, Andrea Arcangeli wrote: > I didn't fill that gap but I was reading the code again and I don't > see why we keep retrying for -EAGAIN in the !sync case. Maybe the > below is good (untested). I doubt it's good to spend cpu to retry the > trylock or to retry the migrate on a pinned page by O_DIRECT. In fact > as far as THP success rate is concerned maybe we should "goto out" > instead of "goto fail" but I didn't change to that as compaction even > if it fails a subpage may still be successful at creating order > 1/2/3/4...8 pages. I only avoid 9 loops to retry a trylock or a page > under O_DIRECT. Maybe that will save a bit of CPU, I doubt it can > decrease the success rate in any significant way. I'll test it at the > next build... At the same time also noticed another minor cleanup (also untested, will text at next build together with some other stuff). === From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: [PATCH] compaction: move ISOLATE_CLEAN setting out of compaction_migratepages loop cc->sync and mode cannot change within the loop so move it out. Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> --- mm/compaction.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 899d956..be0be1d 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -291,6 +291,9 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, return ISOLATE_ABORT; } + if (!cc->sync) + mode |= ISOLATE_CLEAN; + /* Time to isolate some pages for migration */ cond_resched(); spin_lock_irq(&zone->lru_lock); @@ -349,9 +352,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, continue; } - if (!cc->sync) - mode |= ISOLATE_CLEAN; - /* Try isolate the page */ if (__isolate_lru_page(page, mode, 0) != 0) continue; -- 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>