From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f197.google.com (mail-wj0-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 849E86B026B for ; Fri, 6 Jan 2017 11:31:42 -0500 (EST) Received: by mail-wj0-f197.google.com with SMTP id t20so5988823wju.5 for ; Fri, 06 Jan 2017 08:31:42 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id fz16si89691915wjc.184.2017.01.06.08.31.40 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 06 Jan 2017 08:31:41 -0800 (PST) Subject: Re: __GFP_REPEAT usage in fq_alloc_node References: <20170106152052.GS5556@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: <20901069-5eb7-f5ff-0641-078635544531@suse.cz> Date: Fri, 6 Jan 2017 17:31:40 +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 , Michal Hocko Cc: linux-mm@kvack.org, LKML On 01/06/2017 04:39 PM, Eric Dumazet wrote: > On Fri, Jan 6, 2017 at 7:20 AM, Michal Hocko wrote: >> >> Hi Eric, >> I am currently checking kmalloc with vmalloc fallback users and convert >> them to a new kvmalloc helper [1]. While I am adding a support for >> __GFP_REPEAT to kvmalloc [2] I was wondering what is the reason to use >> __GFP_REPEAT in fq_alloc_node in the first place. c3bd85495aef >> ("pkt_sched: fq: more robust memory allocation") doesn't mention >> anything. Could you clarify this please? >> >> Thanks! > > I guess this question applies to all __GFP_REPEAT usages in net/ ? > > At the time, tests on the hardware I had in my labs showed that > vmalloc() could deliver pages spread > all over the memory and that was a small penalty (once memory is > fragmented enough, not at boot time) 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 guess this wont be anymore a concern if I can finish my pending work > about vmalloc() trying to get adjacent pages > https://lkml.org/lkml/2016/12/21/285 > > Thanks. > > -- > 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