From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f42.google.com (mail-qg0-f42.google.com [209.85.192.42]) by kanga.kvack.org (Postfix) with ESMTP id 86D186B0038 for ; Thu, 29 Jan 2015 17:08:19 -0500 (EST) Received: by mail-qg0-f42.google.com with SMTP id q107so35034823qgd.1 for ; Thu, 29 Jan 2015 14:08:19 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id m69si11900311qgm.21.2015.01.29.14.08.17 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Jan 2015 14:08:18 -0800 (PST) Date: Thu, 29 Jan 2015 22:15:21 +0100 From: Andrea Arcangeli Subject: Re: [PATCH v4] mm: incorporate read-only pages into transparent huge pages Message-ID: <20150129211521.GA11755@redhat.com> References: <1422543547-12591-1-git-send-email-ebru.akagunduz@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1422543547-12591-1-git-send-email-ebru.akagunduz@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Ebru Akagunduz Cc: linux-mm@kvack.org, akpm@linux-foundation.org, kirill@shutemov.name, mhocko@suse.cz, mgorman@suse.de, rientjes@google.com, sasha.levin@oracle.com, hughd@google.com, hannes@cmpxchg.org, vbabka@suse.cz, linux-kernel@vger.kernel.org, riel@redhat.com, zhangyanfei.linux@aliyun.com On Thu, Jan 29, 2015 at 04:59:07PM +0200, Ebru Akagunduz wrote: > This patch aims to improve THP collapse rates, by allowing > THP collapse in the presence of read-only ptes, like those > left in place by do_swap_page after a read fault. > > Currently THP can collapse 4kB pages into a THP when > there are up to khugepaged_max_ptes_none pte_none ptes > in a 2MB range. This patch applies the same limit for > read-only ptes. > > The patch was tested with a test program that allocates > 800MB of memory, writes to it, and then sleeps. I force > the system to swap out all but 190MB of the program by > touching other memory. Afterwards, the test program does > a mix of reads and writes to its memory, and the memory > gets swapped back in. > > Without the patch, only the memory that did not get > swapped out remained in THPs, which corresponds to 24% of > the memory of the program. The percentage did not increase > over time. > > With this patch, after 5 minutes of waiting khugepaged had > collapsed 60% of the program's memory back into THPs. > > Signed-off-by: Ebru Akagunduz > Signed-off-by: Ebru Akagunduz > Reviewed-by: Rik van Riel > Acked-by: Vlastimil Babka > Acked-by: Zhang Yanfei Reviewed-by: Andrea Arcangeli -- 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