From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 5D51F6B0034 for ; Mon, 2 Sep 2013 12:37:30 -0400 (EDT) Date: Mon, 02 Sep 2013 12:37:10 -0400 From: Naoya Horiguchi Message-ID: <1378139830-2a95i7nl-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <20130902105327.AE4D4E0090@blue.fi.intel.com> References: <1377883120-5280-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1377883120-5280-3-git-send-email-n-horiguchi@ah.jp.nec.com> <20130902105327.AE4D4E0090@blue.fi.intel.com> Subject: Re: [PATCH 2/2] thp: support split page table lock Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Andi Kleen , Michal Hocko , KOSAKI Motohiro , Rik van Riel , Andrea Arcangeli , "Aneesh Kumar K.V" , Alex Thorlton , linux-kernel@vger.kernel.org Kirill, thank you for the comment. On Mon, Sep 02, 2013 at 01:53:27PM +0300, Kirill A. Shutemov wrote: > Naoya Horiguchi wrote: > > Thp related code also uses per process mm->page_table_lock now. So making > > it fine-grained can provide better performance. > > > > This patch makes thp support split page table lock which makes us use > > page->ptl of the pages storing "pmd_trans_huge" pmds. > > Hm. So, you use page->ptl only when you deal with thp pages, otherwise > mm->page_table_lock, right? Maybe it's not enough. We use page->ptl for both of thp and normal depending on USE_SPLIT_PTLOCKS. And regardless of USE_SPLIT_PTLOCKS, mm->page_table_lock is still used by other contexts like memory initialization code or driver code for their specific usage. > It looks inconsistent to me. Does it mean we have to take both locks on > split and collapse paths? This patch includes the replacement with page->ptl for split/collapse path. > I'm not sure if it's safe to take only > page->ptl for alloc path. Probably not. Right, it's not safe. > Why not to use new locking for pmd everywhere? So I already do this. Thanks, Naoya Horiguchi -- 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