From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 550346B0038 for ; Sun, 8 Jan 2017 22:14:47 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id 204so96314220pfx.1 for ; Sun, 08 Jan 2017 19:14:47 -0800 (PST) Received: from out4435.biz.mail.alibaba.com (out4435.biz.mail.alibaba.com. [47.88.44.35]) by mx.google.com with ESMTP id 17si55378284pfq.99.2017.01.08.19.14.44 for ; Sun, 08 Jan 2017 19:14:46 -0800 (PST) Reply-To: "Hillf Danton" From: "Hillf Danton" References: <20170104111049.15501-1-mgorman@techsingularity.net> <20170104111049.15501-4-mgorman@techsingularity.net> <00ee01d267cc$b61feaa0$225fbfe0$@alibaba-inc.com> <20170106101530.zq7mpvu4uw2dppal@techsingularity.net> In-Reply-To: <20170106101530.zq7mpvu4uw2dppal@techsingularity.net> Subject: Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Date: Mon, 09 Jan 2017 11:14:29 +0800 Message-ID: <019901d26a26$7def6c30$79ce4490$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Language: zh-cn Sender: owner-linux-mm@kvack.org List-ID: To: 'Mel Gorman' Cc: 'Jesper Dangaard Brouer' , 'Linux Kernel' , 'Linux-MM' > Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote: > > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote: > > > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote: > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, > > > struct list_head *list; > > > bool cold = ((gfp_flags & __GFP_COLD) != 0); > > > struct page *page; > > > - unsigned long flags; > > > > > > - local_irq_save(flags); > > > + preempt_disable(); > > > pcp = &this_cpu_ptr(zone->pageset)->pcp; > > > list = &pcp->lists[migratetype]; > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype, > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); > > > zone_statistics(preferred_zone, zone, gfp_flags); > > > } > > > - local_irq_restore(flags); > > > + preempt_enable(); > > > return page; > > > } > > > > > With PREEMPT configured, preempt_enable() adds entry point to schedule(). > > Is that needed when we try to allocate a page? > > > > Not necessarily but what are you proposing as an alternative? preempt_enable_no_resched() looks at first glance a choice for us to avoid flipping interrupts. > get_cpu() > is not an alternative and the point is to avoid disabling interrupts > which is a much more expensive operation. > Agree with every word. Hillf -- 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