From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f42.google.com (mail-yh0-f42.google.com [209.85.213.42]) by kanga.kvack.org (Postfix) with ESMTP id 3FF636B0085 for ; Tue, 21 Jan 2014 17:14:55 -0500 (EST) Received: by mail-yh0-f42.google.com with SMTP id a41so1295660yho.1 for ; Tue, 21 Jan 2014 14:14:55 -0800 (PST) Received: from mail-yh0-x229.google.com (mail-yh0-x229.google.com [2607:f8b0:4002:c01::229]) by mx.google.com with ESMTPS id r4si7757105yhg.10.2014.01.21.14.14.53 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 21 Jan 2014 14:14:54 -0800 (PST) Received: by mail-yh0-f41.google.com with SMTP id i7so2308487yha.28 for ; Tue, 21 Jan 2014 14:14:53 -0800 (PST) Date: Tue, 21 Jan 2014 14:14:51 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat In-Reply-To: Message-ID: References: <20140106204300.DE79BA86@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Andrew Morton , Pekka Enberg On Wed, 8 Jan 2014, David Rientjes wrote: > > There used to be only one path out of __slab_alloc(), and > > ALLOC_SLOWPATH got bumped in that exit path. Now there are two, > > and a bunch of gotos. ALLOC_SLOWPATH can now get set more than once > > during a single call to __slab_alloc() which is pretty bogus. > > Here's the sequence: > > > > 1. Enter __slab_alloc(), fall through all the way to the > > stat(s, ALLOC_SLOWPATH); > > 2. hit 'if (!freelist)', and bump DEACTIVATE_BYPASS, jump to > > new_slab (goto #1) > > 3. Hit 'if (c->partial)', bump CPU_PARTIAL_ALLOC, goto redo > > (goto #2) > > 4. Fall through in the same path we did before all the way to > > stat(s, ALLOC_SLOWPATH) > > 5. bump ALLOC_REFILL stat, then return > > > > Doing this is obviously bogus. It keeps us from being able to > > accurately compare ALLOC_SLOWPATH vs. ALLOC_FASTPATH. It also > > means that the total number of allocs always exceeds the total > > number of frees. > > > > This patch moves stat(s, ALLOC_SLOWPATH) to be called from the > > same place that __slab_alloc() is. This makes it much less > > likely that ALLOC_SLOWPATH will get botched again in the > > spaghetti-code inside __slab_alloc(). > > > > Signed-off-by: Dave Hansen > > Acked-by: David Rientjes > Pekka, are you going to pick this up for linux-next? I think it would be nice to have for 3.14 for those of us who use the stats. -- 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