From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id 272E06B0031 for ; Fri, 4 Oct 2013 03:21:52 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id bj1so3772060pad.0 for ; Fri, 04 Oct 2013 00:21:51 -0700 (PDT) Date: Fri, 4 Oct 2013 09:21:32 +0200 From: Peter Zijlstra Subject: Re: [PATCHv4 09/10] mm: implement split page table lock for PMD level Message-ID: <20131004072132.GT28601@twins.programming.kicks-ass.net> References: <1380287787-30252-1-git-send-email-kirill.shutemov@linux.intel.com> <1380287787-30252-10-git-send-email-kirill.shutemov@linux.intel.com> <20131003161109.aa568784d6fc48e61dc1d33e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131003161109.aa568784d6fc48e61dc1d33e@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: "Kirill A. Shutemov" , Alex Thorlton , Ingo Molnar , Naoya Horiguchi , "Eric W . Biederman" , "Paul E . McKenney" , Al Viro , Andi Kleen , Andrea Arcangeli , Dave Hansen , Dave Jones , David Howells , Frederic Weisbecker , Johannes Weiner , Kees Cook , Mel Gorman , Michael Kerrisk , Oleg Nesterov , Rik van Riel , Robin Holt , Sedat Dilek , Srikar Dronamraju , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, Oct 03, 2013 at 04:11:09PM -0700, Andrew Morton wrote: > On Fri, 27 Sep 2013 16:16:26 +0300 "Kirill A. Shutemov" wrote: > > > The basic idea is the same as with PTE level: the lock is embedded into > > struct page of table's page. > > > > We can't use mm->pmd_huge_pte to store pgtables for THP, since we don't > > take mm->page_table_lock anymore. Let's reuse page->lru of table's page > > for that. > > > > pgtable_pmd_page_ctor() returns true, if initialization is successful > > and false otherwise. Current implementation never fails, but assumption > > that constructor can fail will help to port it to -rt where spinlock_t > > is rather huge and cannot be embedded into struct page -- dynamic > > allocation is required. > > spinlock_t is rather large when lockdep is enabled. What happens? I could go fix all the arch code and pgtable ctor thingies and do the same thing we do on -rt if anybody cares. Hugh thought the single pagetable lock would catch the more interesting locking scenarios, but its of course sad to have an entire locking scheme not covered by lockdep -- that's just waiting for a bug to sneak in there. -- 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