From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb0-f199.google.com (mail-yb0-f199.google.com [209.85.213.199]) by kanga.kvack.org (Postfix) with ESMTP id 7EF026B0387 for ; Thu, 23 Feb 2017 14:05:14 -0500 (EST) Received: by mail-yb0-f199.google.com with SMTP id d88so105467ybi.3 for ; Thu, 23 Feb 2017 11:05:14 -0800 (PST) Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com. [67.231.145.42]) by mx.google.com with ESMTPS id g88si5562786ioj.172.2017.02.23.11.05.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 Feb 2017 11:05:13 -0800 (PST) Date: Thu, 23 Feb 2017 11:04:46 -0800 From: Shaohua Li Subject: Re: [PATCH V4 3/6] mm: move MADV_FREE pages into LRU_INACTIVE_FILE list Message-ID: <20170223190446.GA32825@shli-mbp.local> References: <20170223155827.GB4031@cmpxchg.org> <20170223162601.GA18526@brenorobert-mbp.dhcp.thefacebook.com> <20170223182206.GA5686@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20170223182206.GA5686@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kernel-team@fb.com, mhocko@suse.com, minchan@kernel.org, hughd@google.com, riel@redhat.com, mgorman@techsingularity.net, akpm@linux-foundation.org On Thu, Feb 23, 2017 at 01:22:06PM -0500, Johannes Weiner wrote: > On Thu, Feb 23, 2017 at 08:26:03AM -0800, Shaohua Li wrote: > > On Thu, Feb 23, 2017 at 10:58:27AM -0500, Johannes Weiner wrote: > > > Hi Shaohua, > > > > > > On Wed, Feb 22, 2017 at 10:50:41AM -0800, Shaohua Li wrote: > > > > @@ -268,6 +268,12 @@ static void __activate_page(struct page *page, struct lruvec *lruvec, > > > > int lru = page_lru_base_type(page); > > > > > > > > del_page_from_lru_list(page, lruvec, lru); > > > > + if (PageAnon(page) && !PageSwapBacked(page)) { > > > > + SetPageSwapBacked(page); > > > > + /* charge to anon scanned/rotated reclaim_stat */ > > > > + file = 0; > > > > + lru = LRU_INACTIVE_ANON; > > > > + } > > > > > > As per my previous feedback, please remove this. Write-after-free will > > > be caught and handled in the reclaimer, read-after-free is a bug that > > > really doesn't require optimizing page aging for. And we definitely > > > shouldn't declare invalid data suddenly valid because it's being read. > > > > GUP could run into this. Don't we move the page because it's hot? I think it's > > not just about page aging. If we leave the page there, page reclaim will just > > waste time to reclaim the pages which should't be reclaimed. > > There is just no convincing justification to add this code, because it > optimizes something that doesn't have a real world application. If we > just delete this branch, for all intents and purposes the outcome will > be perfectly acceptable. Ok, looks you want to ignore all corner cases, the gup case is one and the unmap failure and mlock case we discussed before are another. I don't disagree with the intention, but I had the feeling those code will eventually come back. Anyway, I'll delete this code in next post. Thanks, Shaohua -- 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