From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by kanga.kvack.org (Postfix) with ESMTP id 7AB916B00DE for ; Wed, 6 Nov 2013 09:30:53 -0500 (EST) Received: by mail-pa0-f52.google.com with SMTP id bj1so10541388pad.39 for ; Wed, 06 Nov 2013 06:30:53 -0800 (PST) Received: from psmtp.com ([74.125.245.160]) by mx.google.com with SMTP id t6si3474186paa.163.2013.11.06.06.30.50 for ; Wed, 06 Nov 2013 06:30:51 -0800 (PST) Date: Wed, 6 Nov 2013 15:30:37 +0100 From: Peter Zijlstra Subject: Re: [PATCH] mm: create a separate slab for page->ptl allocation Message-ID: <20131106143037.GO10651@twins.programming.kicks-ass.net> References: <1382442839-7458-1-git-send-email-kirill.shutemov@linux.intel.com> <20131105150145.734a5dd5b5d455800ebfa0d3@linux-foundation.org> <20131105224217.GC20167@shutemov.name> <20131105155619.021f32eba1ca8f15a73ed4c9@linux-foundation.org> <20131105231310.GE20167@shutemov.name> <20131106093131.GU28601@twins.programming.kicks-ass.net> <20131106132155.GA22132@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131106132155.GA22132@shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrew Morton , "Kirill A. Shutemov" , Ingo Molnar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org On Wed, Nov 06, 2013 at 03:21:55PM +0200, Kirill A. Shutemov wrote: > On Wed, Nov 06, 2013 at 10:31:31AM +0100, Peter Zijlstra wrote: > > On Wed, Nov 06, 2013 at 01:13:11AM +0200, Kirill A. Shutemov wrote: > > > I would like to get rid of __ptlock_alloc()/__ptlock_free() too, but I > > > don't see a way within C: we need to know sizeof(spinlock_t) on > > > preprocessor stage. > > > > > > We can have a hack on kbuild level: write small helper program to find out > > > sizeof(spinlock_t) before start building and turn it into define. > > > But it's overkill from my POV. And cross-compilation will be a fun. > > > > Ah, I just remembered, we have such a thing! > > Great! > > > @@ -1354,7 +1356,7 @@ static inline bool ptlock_init(struct page *page) > > * slab code uses page->slab_cache and page->first_page (for tail > > * pages), which share storage with page->ptl. > > */ > > - VM_BUG_ON(page->ptl); > > + VM_BUG_ON(*(unsigned long *)&page->ptl); > > Huh? Why not direct cast to unsigned long? > > VM_BUG_ON((unsigned long)page->ptl); I tried, GCC didn't dig that. I think because spinlock_t is a composite type and you cannot cast that to a primitive type. -- 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