From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f44.google.com (mail-la0-f44.google.com [209.85.215.44]) by kanga.kvack.org (Postfix) with ESMTP id 79D006B0038 for ; Wed, 4 Feb 2015 02:13:37 -0500 (EST) Received: by mail-la0-f44.google.com with SMTP id gf13so1216501lab.3 for ; Tue, 03 Feb 2015 23:13:36 -0800 (PST) Received: from fiona.linuxhacker.ru ([217.76.32.60]) by mx.google.com with ESMTPS id a3si582112lah.98.2015.02.03.23.13.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Feb 2015 23:13:35 -0800 (PST) Subject: Re: [PATCH] gfs2: use __vmalloc GFP_NOFS for fs-related allocations. Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=us-ascii From: Oleg Drokin In-Reply-To: <20150203223350.GP6282@dastard> Date: Wed, 4 Feb 2015 02:13:29 -0500 Content-Transfer-Encoding: 7bit Message-Id: References: <1422849594-15677-1-git-send-email-green@linuxhacker.ru> <20150202053708.GG4251@dastard> <20150202081115.GI4251@dastard> <54CF51C5.5050801@redhat.com> <20150203223350.GP6282@dastard> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Chinner Cc: Steven Whitehouse , cluster-devel@redhat.com, Linux Kernel Mailing List , linux-mm@kvack.org Hello! On Feb 3, 2015, at 5:33 PM, Dave Chinner wrote: >> I also wonder if vmalloc is still very slow? That was the case some >> time ago when I noticed a problem in directory access times in gfs2, >> which made us change to use kmalloc with a vmalloc fallback in the >> first place, > Another of the "myths" about vmalloc. The speed and scalability of > vmap/vmalloc is a long solved problem - Nick Piggin fixed the worst > of those problems 5-6 years ago - see the rewrite from 2008 that > started with commit db64fe0 ("mm: rewrite vmap layer").... This actually might be less true than one would hope. At least somewhat recent studies by LLNL (https://jira.hpdd.intel.com/browse/LU-4008) show that there's huge contention on vmlist_lock, so if you have vmalloc intense workloads, you get penalized heavily. Granted, this is rhel6 kernel, but that is still (albeit heavily modified) 2.6.32, which was released at the end of 2009, way after 2008. I see that vmlist_lock is gone now, but e.g. vmap_area_lock that is heavily used is still in place. So of course with that in place there's every incentive to not use vmalloc if at all possible. But if used, one would still hopes it would be at least safe to do even if somewhat slow. Bye, Oleg -- 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