Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754464Ab3IZVm4 (ORCPT ); Thu, 26 Sep 2013 17:42:56 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:59676 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753875Ab3IZVmz (ORCPT ); Thu, 26 Sep 2013 17:42:55 -0400 Message-ID: <5244AA5C.8060100@hurleysoftware.com> Date: Thu, 26 Sep 2013 17:42:52 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Andrew Morton CC: Greg KH , Fengguang Wu , LKML , lkp@01.org, Tejun Heo Subject: Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data" References: <20130913005133.GA32479@localhost> <20130913010936.GA1291@localhost> <5238767D.1080606@hurleysoftware.com> <20130917232214.GA11390@localhost> <5238F252.5070905@hurleysoftware.com> <20130926003315.2e81bc84.akpm@linux-foundation.org> <52441B23.7050704@hurleysoftware.com> <20130926150421.GA25545@kroah.com> <52447064.5030902@hurleysoftware.com> <20130926110551.52ad8156.akpm@linux-foundation.org> In-Reply-To: <20130926110551.52ad8156.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1127 Lines: 28 On 09/26/2013 02:05 PM, Andrew Morton wrote: > On Thu, 26 Sep 2013 13:35:32 -0400 Peter Hurley wrote: > >> The issue with a single large kmalloc is that it may fail where >> 3 separate, page-or-less kmallocs would not have. > > Or vmalloc fails first, because of internal fragmentation of the vmap > arena. This problem plus vmalloc's slowness are the reasons why > vmalloc should be avoided. Ok, no vmalloc. > A tremendous number of places in the kernel perform higher-order > allocations nowadays. The page allocator works damn hard to service > them and I expect that switching to kmalloc here will be OK. I've had order-4 allocation failures before on 10Gb. In fact, the nouveau driver switched to vmalloc for that very reason (commit d005f51eb93d71cd40ebd11dd377453fa8c8a42a, drm/nouveau: use vmalloc for pgt allocation). Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/