From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f199.google.com (mail-wj0-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id 399F26B0069 for ; Fri, 6 Jan 2017 11:55:25 -0500 (EST) Received: by mail-wj0-f199.google.com with SMTP id sr6so6603891wjb.2 for ; Fri, 06 Jan 2017 08:55:25 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id d10si3112838wmi.71.2017.01.06.08.55.23 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 06 Jan 2017 08:55:24 -0800 (PST) Subject: Re: __GFP_REPEAT usage in fq_alloc_node References: <20170106152052.GS5556@dhcp22.suse.cz> <20901069-5eb7-f5ff-0641-078635544531@suse.cz> From: Vlastimil Babka Message-ID: <97be60da-72df-ad8f-db03-03f01c392823@suse.cz> Date: Fri, 6 Jan 2017 17:55:23 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Eric Dumazet Cc: Michal Hocko , linux-mm@kvack.org, LKML On 01/06/2017 05:48 PM, Eric Dumazet wrote: > On Fri, Jan 6, 2017 at 8:31 AM, Vlastimil Babka wrote: > >> >> I wonder what's that cause of the penalty (when accessing the vmapped >> area I suppose?) Is it higher risk of collisions cache misses within the >> area, compared to consecutive physical adresses? > > I believe tests were done with 48 fq qdisc, each having 2^16 slots. > So I had 48 blocs,of 524288 bytes. > > Trying a bit harder at setup time to get 128 consecutive pages got > less TLB pressure. Hmm that's rather surprising to me. TLB caches the page table lookups and the PFN's of the physical pages it translates to shouldn't matter - the page tables will look the same. With 128 consecutive pages could manifest the reduced collision cache miss effect though. > -- > 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 > -- 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