From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753369AbdGXMjD (ORCPT ); Mon, 24 Jul 2017 08:39:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:33002 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751610AbdGXMiy (ORCPT ); Mon, 24 Jul 2017 08:38:54 -0400 Date: Mon, 24 Jul 2017 14:38:43 +0200 From: Michal Hocko To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Andrew Morton , Mel Gorman , Yang Shi , Laura Abbott , Vinayak Menon , zhong jiang Subject: Re: [PATCH 1/4] mm, page_owner: make init_pages_in_zone() faster Message-ID: <20170724123843.GH25221@dhcp22.suse.cz> References: <20170720134029.25268-1-vbabka@suse.cz> <20170720134029.25268-2-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170720134029.25268-2-vbabka@suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 20-07-17 15:40:26, Vlastimil Babka wrote: > In init_pages_in_zone() we currently use the generic set_page_owner() function > to initialize page_owner info for early allocated pages. This means we > needlessly do lookup_page_ext() twice for each page, and more importantly > save_stack(), which has to unwind the stack and find the corresponding stack > depot handle. Because the stack is always the same for the initialization, > unwind it once in init_pages_in_zone() and reuse the handle. Also avoid the > repeated lookup_page_ext(). Yes this looks like an improvement but I have to admit that I do not really get why we even do save_stack at all here. Those pages might got allocated from anywhere so we could very well provide a statically allocated "fake" stack trace, no? Memory allocated for the stackdepot storage can be tracked inside depot_alloc_stack as well I guess (again with a statically preallocated storage). > This can significantly reduce boot times with page_owner=on on large machines, > especially for kernels built without frame pointer, where the stack unwinding > is noticeably slower. Some numbders would be really nice here > Signed-off-by: Vlastimil Babka > --- > mm/page_owner.c | 19 ++++++++++++++++++- > 1 file changed, 18 insertions(+), 1 deletion(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 401feb070335..5aa21ca237d9 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -183,6 +183,20 @@ noinline void __set_page_owner(struct page *page, unsigned int order, > __set_bit(PAGE_EXT_OWNER, &page_ext->flags); > } > > +static void __set_page_owner_init(struct page_ext *page_ext, > + depot_stack_handle_t handle) > +{ > + struct page_owner *page_owner; > + > + page_owner = get_page_owner(page_ext); > + page_owner->handle = handle; > + page_owner->order = 0; > + page_owner->gfp_mask = 0; > + page_owner->last_migrate_reason = -1; > + > + __set_bit(PAGE_EXT_OWNER, &page_ext->flags); > +} Do we need to duplicated a part of __set_page_owner? Can we pull out both owner and handle out __set_page_owner? -- Michal Hocko SUSE Labs