From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx163.postini.com [74.125.245.163]) by kanga.kvack.org (Postfix) with SMTP id 675586B0031 for ; Wed, 5 Jun 2013 16:18:48 -0400 (EDT) Message-ID: <51AF9D1D.6030709@redhat.com> Date: Wed, 05 Jun 2013 16:18:37 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 5/7] mm: compaction: increase the high order pages in the watermarks References: <1370445037-24144-1-git-send-email-aarcange@redhat.com> <1370445037-24144-6-git-send-email-aarcange@redhat.com> In-Reply-To: <1370445037-24144-6-git-send-email-aarcange@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: linux-mm@kvack.org, Mel Gorman , Hugh Dickins , Richard Davies , Shaohua Li , Rafael Aquini On 06/05/2013 11:10 AM, Andrea Arcangeli wrote: > Require more high order pages in the watermarks, to give more margin > for concurrent allocations. If there are too few pages, they can > disappear too soon. Not sure what to do with this patch. Not scaling min for pageblock_order-2 allocations seems like it could be excessive. Presumably this scaling was introduced for a good reason. Why is that reason no longer valid? Why is it safe to make this change? Would it be safer to simply scale min less steeply? > Signed-off-by: Andrea Arcangeli > --- > mm/page_alloc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3931d16..c13e062 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1646,7 +1646,8 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark, > free_pages -= z->free_area[o].nr_free << o; > > /* Require fewer higher order pages to be free */ > - min >>= 1; > + if (o >= pageblock_order-1) > + min >>= 1; Why this and not this? if (order & 1) min >>=1; Not saying my idea is any better than yours, just saying that a change like this needs more justification than provided by your changelog... > > if (free_pages <= min) > return false; > -- All rights reversed -- 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