From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id C78B78D003B for ; Fri, 8 Apr 2011 16:07:35 -0400 (EDT) Message-ID: <4D9F6AB6.6000809@fiec.espol.edu.ec> Date: Fri, 08 Apr 2011 15:06:14 -0500 From: =?ISO-8859-1?Q?Alex_Villac=ED=ADs_Lasso?= MIME-Version: 1.0 Subject: Re: [Bugme-new] [Bug 31142] New: Large write to USB stick freezes unrelated tasks for a long time References: <20110321163742.GA24244@csn.ul.ie> <4D878564.6080608@fiec.espol.edu.ec> <20110321201641.GA5698@random.random> <20110322112032.GD24244@csn.ul.ie> <20110322150314.GC5698@random.random> <4D8907C2.7010304@fiec.espol.edu.ec> <20110322214020.GD5698@random.random> <20110323003718.GH5698@random.random> <4D8A2517.3090403@fiec.espol.edu.ec> <4D99E5C8.7090505@fiec.espol.edu.ec> <20110408190912.GI29444@random.random> In-Reply-To: <20110408190912.GI29444@random.random> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Mel Gorman , Andrew Morton , avillaci@ceibo.fiec.espol.edu.ec, bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, linux-mm@kvack.org El 08/04/11 14:09, Andrea Arcangeli escribio: > Hi Alex, > > On Mon, Apr 04, 2011 at 10:37:44AM -0500, Alex Villaci-s Lasso wrote: >> Latest update: with 2.6.39-rc1 the stalls only last for a few >> seconds, but they are still there. So, as I said before, they are >> reduced but not eliminated. > Ok from a complete stall for the whole duration of the I/O to a few > second stall we're clearly going into the right direction. > > The few second stalls happen with udf? And vfat doesn't stall? > > Minchan rightly pointed out that the (panik) change we made in > page_alloc.c changes the semantics of the __GFP_NO_KSWAPD bit. I also > talked with Mel about it. We think it's nicer if we can keep THP > allocations as close as any other high order allocation as > possible. There are already plenty of __GFP bits with complex > semantics. __GFP_NO_KSWAPD is simple and it's nice to stay simple: it > means the allocation relies on a different kernel daemon for the > background work (which is khugepaged instead of kswapd in the THP > case, where khugepaged uses a non intrusive alloc_sleep_millisec > throttling in case of MM congestion, unlike kswapd would do). > > So this is no solution to your problem (if vfat already works I think > that might be a better solution), but we'd like to know if you get any > _worse_ stall compared to current 2.6.39-rc, by applying the below > patch on top of 2.6.39-rc. If this doesn't make any difference, we can > safely apply it to remove unnecessary complications. > > Thanks, > Andrea > > === > Subject: compaction: reverse the change that forbid sync migraton with __GFP_NO_KSWAPD > > From: Andrea Arcangeli > > It's uncertain this has been beneficial, so it's safer to undo it. All other > compaction users would still go in synchronous mode if a first attempt of async > compaction failed. Hopefully we don't need to force special behavior for THP > (which is the only __GFP_NO_KSWAPD user so far and it's the easier to exercise > and to be noticeable). This also make __GFP_NO_KSWAPD return to its original > strict semantics specific to bypass kswapd, as THP allocations have khugepaged > for the async THP allocations/compactions. > > Signed-off-by: Andrea Arcangeli > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2105,7 +2105,7 @@ rebalance: > sync_migration); > if (page) > goto got_pg; > - sync_migration = !(gfp_mask& __GFP_NO_KSWAPD); > + sync_migration = true; > > /* Try direct reclaim and then allocating */ > page = __alloc_pages_direct_reclaim(gfp_mask, order, > The stalls occur even with vfat. I am no longer using udf, since (right now) it is not necessary. I will test this patch now. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org