From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kirill A. Shutemov" Subject: Re: [PATCH 34/34] mm: dynamically allocate page->ptl if it cannot be embedded to struct page Date: Mon, 14 Oct 2013 12:04:37 +0300 (EEST) Message-ID: <20131014090437.F22CBE0090@blue.fi.intel.com> References: <1381428359-14843-1-git-send-email-kirill.shutemov@linux.intel.com> <1381428359-14843-35-git-send-email-kirill.shutemov@linux.intel.com> <00000141a3f48ada-37ee9c14-2f2b-40a2-93f4-70258363351b-000000@email.amazonses.com> <20131010200921.91D84E0090@blue.fi.intel.com> <00000141a7d2aa7b-e59f292a-746c-4f55-aa51-9fa060a7fbeb-000000@email.amazonses.com> Content-Transfer-Encoding: 7bit Return-path: Received: from mga03.intel.com ([143.182.124.21]:42674 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754376Ab3JNJEm (ORCPT ); Mon, 14 Oct 2013 05:04:42 -0400 In-Reply-To: <00000141a7d2aa7b-e59f292a-746c-4f55-aa51-9fa060a7fbeb-000000@email.amazonses.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Christoph Lameter Cc: "Kirill A. Shutemov" , Andrew Morton , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org Christoph Lameter wrote: > On Thu, 10 Oct 2013, Kirill A. Shutemov wrote: > > > Christoph Lameter wrote: > > > On Thu, 10 Oct 2013, Kirill A. Shutemov wrote: > > > > > > > +static inline bool ptlock_alloc(struct page *page) > > > > +{ > > > > + if (sizeof(spinlock_t) > sizeof(page->ptl)) > > > > + return __ptlock_alloc(page); > > > > + return true; > > > > +} > > > > > > Could you make the check a CONFIG option? CONFIG_PTLOCK_DOES_NOT_FIT_IN_PAGE_STRUCT or > > > so? > > > > No. We will have to track what affects sizeof(spinlock_t) manually. > > Not a fun and error prune. > > You can generate a config option depending on the size of the object via > Kbuild. Kbuild will determine the setting before building the kernel as a > whole by runing some small C program. I don't think it's any better than what we have there now. -- Kirill A. Shutemov