From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 7 Mar 2006 15:26:36 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: yield during swap prefetching Message-Id: <20060307152636.1324a5b5.akpm@osdl.org> In-Reply-To: <200603081013.44678.kernel@kolivas.org> References: <200603081013.44678.kernel@kolivas.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Con Kolivas Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, ck@vds.kolivas.org List-ID: Con Kolivas wrote: > > Swap prefetching doesn't use very much cpu but spends a lot of time waiting on > disk in uninterruptible sleep. This means it won't get preempted often even at > a low nice level since it is seen as sleeping most of the time. We want to > minimise its cpu impact so yield where possible. > > Signed-off-by: Con Kolivas > --- > mm/swap_prefetch.c | 1 + > 1 file changed, 1 insertion(+) > > Index: linux-2.6.15-ck5/mm/swap_prefetch.c > =================================================================== > --- linux-2.6.15-ck5.orig/mm/swap_prefetch.c 2006-03-02 14:00:46.000000000 +1100 > +++ linux-2.6.15-ck5/mm/swap_prefetch.c 2006-03-08 08:49:32.000000000 +1100 > @@ -421,6 +421,7 @@ static enum trickle_return trickle_swap( > > if (trickle_swap_cache_async(swp_entry, node) == TRICKLE_DELAY) > break; > + yield(); > } > > if (sp_stat.prefetched_pages) { yield() really sucks if there are a lot of runnable tasks. And the amount of CPU which that thread uses isn't likely to matter anyway. I think it'd be better to just not do this. Perhaps alter the thread's static priority instead? Does the scheduler have a knob which can be used to disable a tasks's dynamic priority boost heuristic? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org