From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f48.google.com (mail-pb0-f48.google.com [209.85.160.48]) by kanga.kvack.org (Postfix) with ESMTP id C6C1D6B0031 for ; Mon, 18 Nov 2013 15:20:32 -0500 (EST) Received: by mail-pb0-f48.google.com with SMTP id md12so806500pbc.21 for ; Mon, 18 Nov 2013 12:20:32 -0800 (PST) Received: from psmtp.com ([74.125.245.175]) by mx.google.com with SMTP id z1si10495448pbn.91.2013.11.18.12.20.29 for ; Mon, 18 Nov 2013 12:20:30 -0800 (PST) Date: Mon, 18 Nov 2013 15:20:22 -0500 From: Naoya Horiguchi Message-ID: <1384806022-4718p9lh-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <528A6448.3080907@sr71.net> References: <20131115225550.737E5C33@viggo.jf.intel.com> <20131115225553.B0E9DFFB@viggo.jf.intel.com> <1384800714-y653r3ch-mutt-n-horiguchi@ah.jp.nec.com> <1384800841-314l1f3e-mutt-n-horiguchi@ah.jp.nec.com> <528A6448.3080907@sr71.net> Subject: Re: [PATCH] mm: call cond_resched() per MAX_ORDER_NR_PAGES pages copy Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave.jiang@intel.com, akpm@linux-foundation.org, dhillf@gmail.com, Mel Gorman On Mon, Nov 18, 2013 at 11:02:32AM -0800, Dave Hansen wrote: > On 11/18/2013 10:54 AM, Naoya Horiguchi wrote: > > diff --git a/mm/migrate.c b/mm/migrate.c > > index cb5d152b58bc..661ff5f66591 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -454,7 +454,8 @@ static void __copy_gigantic_page(struct page *dst, struct page *src, > > struct page *src_base = src; > > > > for (i = 0; i < nr_pages; ) { > > - cond_resched(); > > + if (i % MAX_ORDER_NR_PAGES == 0) > > + cond_resched(); > > copy_highpage(dst, src); > > This is certainly OK on x86, but remember that MAX_ORDER can be > overridden by a config variable. Just picking one at random: > > config FORCE_MAX_ZONEORDER > int "Maximum zone order" > range 9 64 if PPC64 && PPC_64K_PAGES > ... > > Would it be OK to only resched once every 2^63 pages? ;) You're right. We need use more reliable value here. HPAGE_SIZE/PAGE_SIZE looks better to me. > Really, though, a lot of things seem to have MAX_ORDER set up so that > it's at 256MB or 512MB. That's an awful lot to do between rescheds. Yes. BTW, I found that we have the same problem for other functions like copy_user_gigantic_page, copy_user_huge_page, and maybe clear_gigantic_page. So we had better handle them too. Thanks, Naoya -- 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