From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f54.google.com (mail-qa0-f54.google.com [209.85.216.54]) by kanga.kvack.org (Postfix) with ESMTP id 4E72E6B006C for ; Thu, 11 Dec 2014 08:35:30 -0500 (EST) Received: by mail-qa0-f54.google.com with SMTP id i13so3483263qae.41 for ; Thu, 11 Dec 2014 05:35:30 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id e5si1268896qcm.34.2014.12.11.05.35.28 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Dec 2014 05:35:29 -0800 (PST) Date: Thu, 11 Dec 2014 14:35:18 +0100 From: Jesper Dangaard Brouer Subject: Re: [PATCH 0/7] slub: Fastpath optimization (especially for RT) V1 Message-ID: <20141211143518.02c781ee@redhat.com> In-Reply-To: <20141210163017.092096069@linux.com> References: <20141210163017.092096069@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: akpm@linuxfoundation.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, Thomas Gleixner , linux-mm@kvack.org, penberg@kernel.org, iamjoonsoo.kim@lge.com, brouer@redhat.com On Wed, 10 Dec 2014 10:30:17 -0600 Christoph Lameter wrote: [...] > > Slab Benchmarks on a kernel with CONFIG_PREEMPT show an improvement of > 20%-50% of fastpath latency: > > Before: > > Single thread testing [...] > 2. Kmalloc: alloc/free test [...] > 10000 times kmalloc(256)/kfree -> 116 cycles [...] > > > After: > > Single thread testing [...] > 2. Kmalloc: alloc/free test [...] > 10000 times kmalloc(256)/kfree -> 60 cycles [...] It looks like an impressive saving 116 -> 60 cycles. I just don't see the same kind of improvements with my similar tests[1][2]. My test[1] is just a fast-path loop over kmem_cache_alloc+free on 256bytes objects. (Results after explicitly inlining new func is_pointer_to_page()) baseline: 47 cycles(tsc) 19.032 ns patchset: 45 cycles(tsc) 18.135 ns I do see the improvement, but it is not as high as I would have expected. (CPU E5-2695) [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/time_bench_kmem_cache1.c [2] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/qmempool_bench.c -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- 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