Mel Gorman <mgor...@techsingularity.net> writes: > On Thu, Dec 03, 2015 at 04:46:53PM +0800, Huang, Ying wrote: >> Mel Gorman <mgor...@techsingularity.net> writes: >> >> > On Wed, Dec 02, 2015 at 03:15:29PM +0100, Michal Hocko wrote: >> >> > > I didn't mention this allocation failure because I am not sure it is >> >> > > really related. >> >> > > >> >> > >> >> > I'm fairly sure it is. The failure is an allocation site that cannot >> >> > sleep but did not specify __GFP_HIGH. >> >> >> >> yeah but this was the case even before your patch. As the caller used >> >> GFP_ATOMIC then it got __GFP_ATOMIC after your patch so it still >> >> managed to do ALLOC_HARDER. I would agree if this was an explicit >> >> GFP_NOWAIT. Unless I am missing something your patch hasn't changed the >> >> behavior for this particular allocation. >> >> >> > >> > You're right. I think it's this hunk that is the problem. >> > >> > @@ -1186,7 +1186,7 @@ static struct request *blk_mq_map_request(struct >> > request_queue *q, >> > ctx = blk_mq_get_ctx(q); >> > hctx = q->mq_ops->map_queue(q, ctx->cpu); >> > blk_mq_set_alloc_data(&alloc_data, q, >> > - __GFP_WAIT|GFP_ATOMIC, false, ctx, hctx); >> > + __GFP_WAIT|__GFP_HIGH, false, ctx, hctx); >> > rq = __blk_mq_alloc_request(&alloc_data, rw); >> > ctx = alloc_data.ctx; >> > hctx = alloc_data.hctx; >> > >> > This specific path at this patch is not waking kswapd any more when it >> > should. A series of allocations there could hit the watermarks and never >> > wake >> > kswapd and then be followed by an atomic allocation failure that woke >> > kswapd. >> > >> > This bug gets fixed later by the commit 71baba4b92dc ("mm, page_alloc: >> > rename __GFP_WAIT to __GFP_RECLAIM") so it's not a bug in the current >> > kernel. However, it happens to break bisection and would be caught if each >> > individual commit was tested. >> > >> > Your __GFP_HIGH patch is still fine although not the direct fix for this >> > specific problem. Commit 71baba4b92dc is. >> > >> > Ying, does the page allocation failure messages happen when the whole >> > series is applied? i.e. is 4.4-rc3 ok? >> >> There are allocation errors for 4.4-rc3 too. dmesg is attached. >> > > What is the result of the __GFP_HIGH patch to give it access to > reserves?
Applied Michal's patch on v4.4-rc3 and tested again, now there is no page allocation failure. Best Regards, Huang, Ying -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/