From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f169.google.com (mail-yk0-f169.google.com [209.85.160.169]) by kanga.kvack.org (Postfix) with ESMTP id 3942A6B0032 for ; Thu, 4 Dec 2014 12:57:18 -0500 (EST) Received: by mail-yk0-f169.google.com with SMTP id 79so8232858ykr.0 for ; Thu, 04 Dec 2014 09:57:18 -0800 (PST) Received: from mail-qc0-x230.google.com (mail-qc0-x230.google.com. [2607:f8b0:400d:c01::230]) by mx.google.com with ESMTPS id g75si32067026qge.83.2014.12.04.09.57.16 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 04 Dec 2014 09:57:17 -0800 (PST) Received: by mail-qc0-f176.google.com with SMTP id i17so13182565qcy.21 for ; Thu, 04 Dec 2014 09:57:16 -0800 (PST) Date: Thu, 4 Dec 2014 12:57:13 -0500 From: Tejun Heo Subject: Re: [RFC v2] percpu: Add a separate function to merge free areas Message-ID: <20141204175713.GE2995@htj.dyndns.org> References: <547E3E57.3040908@ixiacom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <547E3E57.3040908@ixiacom.com> Sender: owner-linux-mm@kvack.org List-ID: To: Leonard Crestez Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Sorin Dumitru Hello, On Wed, Dec 03, 2014 at 12:33:59AM +0200, Leonard Crestez wrote: > It seems that free_percpu performance is very bad when working with small > objects. The easiest way to reproduce this is to allocate and then free a large > number of percpu int counters in order. Small objects (reference counters and > pointers) are common users of alloc_percpu and I think this should be fast. > This particular issue can be encountered with very large number of net_device > structs. Do you actually experience this with an actual workload? The thing is allocation has the same quadratic complexity. If this is actually an issue (which can definitely be the case), I'd much prefer implementing a properly scalable area allocator than mucking with the current implementation. Thanks. -- tejun -- 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