From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757610AbbA0Ie5 (ORCPT ); Tue, 27 Jan 2015 03:34:57 -0500 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:59987 "EHLO lgemrelse7q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754030AbbA0Iez (ORCPT ); Tue, 27 Jan 2015 03:34:55 -0500 X-Original-SENDERIP: 10.177.222.153 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Tue, 27 Jan 2015 17:36:12 +0900 From: Joonsoo Kim To: Sergei Rogachev Cc: akpm@linux-foundation.org, LKML Subject: Re: [PATCH 1/1] mm/page_ext: remove unnecessary stack_trace field Message-ID: <20150127083612.GG11358@js1304-P5Q-DELUXE> References: <1422309132-28030-1-git-send-email-rogachevsergei@gmail.com> <1422309132-28030-2-git-send-email-rogachevsergei@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1422309132-28030-2-git-send-email-rogachevsergei@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 27, 2015 at 12:52:12AM +0300, Sergei Rogachev wrote: > Page owner uses the page_ext structure to keep meta-information > for every page in the system. The structure also contains a field > of type 'struct stack_trace', page owner uses this field during > invocation of the function save_stack_trace. It is easy to notice > that keeping a copy of this structure for every page in the system > is very inefficiently in terms of memory. > > The patch removes this unnecessary field of page_ext and forces > page owner to use a stack_trace structure allocated on the stack. > > Signed-off-by: Sergei Rogachev > --- > include/linux/page_ext.h | 2 +- > mm/page_owner.c | 21 ++++++++++++--------- > 2 files changed, 13 insertions(+), 10 deletions(-) > > diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h > index d2a2c84..c42981c 100644 > --- a/include/linux/page_ext.h > +++ b/include/linux/page_ext.h > @@ -40,7 +40,7 @@ struct page_ext { > #ifdef CONFIG_PAGE_OWNER > unsigned int order; > gfp_t gfp_mask; > - struct stack_trace trace; > + unsigned int nr_entries; > unsigned long trace_entries[8]; > #endif > }; > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 9ab4a9b..f7f3318 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -60,19 +60,19 @@ void __reset_page_owner(struct page *page, unsigned int order) > void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask) > { > struct page_ext *page_ext; > - struct stack_trace *trace; > + struct stack_trace trace; > > page_ext = lookup_page_ext(page); > > - trace = &page_ext->trace; > - trace->nr_entries = 0; > - trace->max_entries = ARRAY_SIZE(page_ext->trace_entries); > - trace->entries = &page_ext->trace_entries[0]; > - trace->skip = 3; > - save_stack_trace(&page_ext->trace); > + trace.nr_entries = 0; > + trace.max_entries = ARRAY_SIZE(page_ext->trace_entries); > + trace.entries = &page_ext->trace_entries[0]; > + trace.skip = 3; > + save_stack_trace(&trace); > > page_ext->order = order; > page_ext->gfp_mask = gfp_mask; > + page_ext->nr_entries = trace.nr_entries; > > __set_bit(PAGE_EXT_OWNER, &page_ext->flags); > } > @@ -83,6 +83,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, > { > int ret; > int pageblock_mt, page_mt; > + struct stack_trace trace; > char *kbuf; > > kbuf = kmalloc(count, GFP_KERNEL); > @@ -121,8 +122,10 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, > if (ret >= count) > goto err; > > - ret += snprint_stack_trace(kbuf + ret, count - ret, > - &page_ext->trace, 0); > + trace.nr_entries = page_ext->nr_entries; > + trace.entries = &page_ext->trace_entries[0]; > + > + ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0); > if (ret >= count) > goto err; Acked-by: Joonsoo Kim Thanks.