From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id 5E5556B0032 for ; Mon, 15 Jun 2015 02:08:24 -0400 (EDT) Received: by wgez8 with SMTP id z8so60031609wge.0 for ; Sun, 14 Jun 2015 23:08:24 -0700 (PDT) Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com. [209.85.212.180]) by mx.google.com with ESMTPS id es2si16597539wib.45.2015.06.14.23.08.22 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 14 Jun 2015 23:08:23 -0700 (PDT) Received: by wicnd19 with SMTP id nd19so13907536wic.1 for ; Sun, 14 Jun 2015 23:08:22 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <557E65E7.9010000@redhat.com> References: <1434294283-8699-1-git-send-email-ebru.akagunduz@gmail.com> <1434294283-8699-3-git-send-email-ebru.akagunduz@gmail.com> <557E65E7.9010000@redhat.com> From: Leon Romanovsky Date: Mon, 15 Jun 2015 09:08:02 +0300 Message-ID: Subject: Re: [RFC 2/3] mm: make optimistic check for swapin readahead Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Ebru Akagunduz , Linux-MM , Andrew Morton , "kirill.shutemov" , n-horiguchi , aarcange , "iamjoonsoo.kim" , Xiexiuqi , gorcunov , "linux-kernel@vger.kernel.org" , Mel Gorman , rientjes , Vlastimil Babka , "aneesh.kumar" , hughd , Johannes Weiner , mhocko , boaz , raindel On Mon, Jun 15, 2015 at 8:43 AM, Rik van Riel wrote: > On 06/15/2015 01:40 AM, Leon Romanovsky wrote: >> On Sun, Jun 14, 2015 at 6:04 PM, Ebru Akagunduz >> wrote: >>> This patch makes optimistic check for swapin readahead >>> to increase thp collapse rate. Before getting swapped >>> out pages to memory, checks them and allows up to a >>> certain number. It also prints out using tracepoints >>> amount of unmapped ptes. >>> >>> Signed-off-by: Ebru Akagunduz > >>> @@ -2639,11 +2640,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, >>> { >>> pmd_t *pmd; >>> pte_t *pte, *_pte; >>> - int ret = 0, none_or_zero = 0; >>> + int ret = 0, none_or_zero = 0, unmapped = 0; >>> struct page *page; >>> unsigned long _address; >>> spinlock_t *ptl; >>> - int node = NUMA_NO_NODE; >>> + int node = NUMA_NO_NODE, max_ptes_swap = HPAGE_PMD_NR/8; >> Sorry for asking, my knoweldge of THP is very limited, but why did you >> choose this default value? >> From the discussion followed by your patch >> (https://lkml.org/lkml/2015/2/27/432), I got an impression that it is >> not necessary right value. > > I believe that Ebru's main focus for this initial version of > the patch series was to get the _mechanism_ (patch 3) right, > while having a fairly simple policy to drive it. > > Any suggestions on when it is a good idea to bring in pages > from swap, and whether to treat resident-in-swap-cache pages > differently from need-to-be-paged-in pages, and what other > factors should be examined, are very welcome... My concern with these patches that they deal with specific load/scenario (most of the application returned back from swap). In scenario there only 10% of data will be required, it theoretically can bring upto 80% data (70% waste). > > -- > All rights reversed -- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon@leon.nu -- 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