From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id BC110280757 for ; Wed, 23 Aug 2017 02:47:41 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id x6so1359124wme.4 for ; Tue, 22 Aug 2017 23:47:41 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 199si840502wma.60.2017.08.22.23.47.39 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 22 Aug 2017 23:47:40 -0700 (PDT) Subject: Re: [PATCH 1/4] mm, page_owner: make init_pages_in_zone() faster References: <20170720134029.25268-1-vbabka@suse.cz> <20170720134029.25268-2-vbabka@suse.cz> <20170724123843.GH25221@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: <483227ce-6786-f04b-72d1-dba18e06ccaa@suse.cz> Date: Wed, 23 Aug 2017 08:47:37 +0200 MIME-Version: 1.0 In-Reply-To: <20170724123843.GH25221@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Andrew Morton , Mel Gorman , Yang Shi , Laura Abbott , Vinayak Menon , zhong jiang On 07/24/2017 02:38 PM, Michal Hocko wrote: > 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? We could, but it's much simpler to do it this way than try to extend stack depot/stack saving to support creating such fakes. Would it be worth the effort? > Memory allocated for the stackdepot storage can be tracked inside > depot_alloc_stack as well I guess (again with a statically preallocated > storage). I'm not sure I get your point here? The pages we have to "fake" are not just the stackdepot storage itself, but everything that has been allocated before the page_owner is initialized. >> 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 Well, the problem was that on a 3TB machine I just gave up and rebooted it after ~30 minutes of waiting for the init to finish. After this patch it was maybe 5 minutes. >> 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? I wanted to avoid overhead in __set_page_owner() by introducing extra shared function, but I'll check if that can be helped. -- 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