From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f182.google.com (mail-ie0-f182.google.com [209.85.223.182]) by kanga.kvack.org (Postfix) with ESMTP id AEB2E6B0071 for ; Wed, 17 Dec 2014 11:10:47 -0500 (EST) Received: by mail-ie0-f182.google.com with SMTP id x19so15204337ier.27 for ; Wed, 17 Dec 2014 08:10:47 -0800 (PST) Received: from resqmta-po-01v.sys.comcast.net (resqmta-po-01v.sys.comcast.net. [2001:558:fe16:19:96:114:154:160]) by mx.google.com with ESMTPS id b1si3123703ioj.45.2014.12.17.08.10.46 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Wed, 17 Dec 2014 08:10:46 -0800 (PST) Date: Wed, 17 Dec 2014 10:10:43 -0600 (CST) From: Christoph Lameter Subject: Re: [PATCH 0/7] slub: Fastpath optimization (especially for RT) V1 In-Reply-To: Message-ID: References: <20141210163017.092096069@linux.com> <20141215075933.GD4898@js1304-P5Q-DELUXE> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Joonsoo Kim , akpm@linuxfoundation.org, Steven Rostedt , LKML , Thomas Gleixner , Linux Memory Management List , Pekka Enberg , Jesper Dangaard Brouer On Wed, 17 Dec 2014, Joonsoo Kim wrote: > + do { > + tid = this_cpu_read(s->cpu_slab->tid); > + c = this_cpu_ptr(s->cpu_slab); > + } while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid)); Assembly code produced is a bit weird. I think the compiler undoes what you wanted to do: 46fb: 49 8b 1e mov (%r14),%rbx rbx = c =s->cpu_slab? 46fe: 65 4c 8b 6b 08 mov %gs:0x8(%rbx),%r13 r13 = tid 4703: e8 00 00 00 00 callq 4708 ?? 4708: 89 c0 mov %eax,%eax ?? 470a: 48 03 1c c5 00 00 00 add 0x0(,%rax,8),%rbx ?? 4711: 00 4712: 4c 3b 6b 08 cmp 0x8(%rbx),%r13 tid == c->tid 4716: 49 89 d8 mov %rbx,%r8 4719: 75 e0 jne 46fb -- 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