From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753576AbdGNJg4 (ORCPT ); Fri, 14 Jul 2017 05:36:56 -0400 Received: from mx2.suse.de ([195.135.220.15]:54536 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751353AbdGNJgy (ORCPT ); Fri, 14 Jul 2017 05:36:54 -0400 Date: Fri, 14 Jul 2017 10:36:50 +0100 From: Mel Gorman To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , Johannes Weiner , Vlastimil Babka , LKML , Michal Hocko , linux-api@vger.kernel.org Subject: Re: [PATCH 1/9] mm, page_alloc: rip out ZONELIST_ORDER_ZONE Message-ID: <20170714093650.l67vbem2g4typkta@suse.de> References: <20170714080006.7250-1-mhocko@kernel.org> <20170714080006.7250-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170714080006.7250-2-mhocko@kernel.org> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 14, 2017 at 09:59:58AM +0200, Michal Hocko wrote: > From: Michal Hocko > > Supporting zone ordered zonelists costs us just a lot of code while > the usefulness is arguable if existent at all. Mel has already made > node ordering default on 64b systems. 32b systems are still using > ZONELIST_ORDER_ZONE because it is considered better to fallback to > a different NUMA node rather than consume precious lowmem zones. > > This argument is, however, weaken by the fact that the memory reclaim > has been reworked to be node rather than zone oriented. This means > that lowmem requests have to skip over all highmem pages on LRUs already > and so zone ordering doesn't save the reclaim time much. So the only > advantage of the zone ordering is under a light memory pressure when > highmem requests do not ever hit into lowmem zones and the lowmem > pressure doesn't need to reclaim. > > Considering that 32b NUMA systems are rather suboptimal already and > it is generally advisable to use 64b kernel on such a HW I believe we > should rather care about the code maintainability and just get rid of > ZONELIST_ORDER_ZONE altogether. Keep systcl in place and warn if > somebody tries to set zone ordering either from kernel command line > or the sysctl. > > Cc: > Signed-off-by: Michal Hocko > index 80e4adb4c360..d9f4ea057e74 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4864,40 +4824,22 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write, > void __user *buffer, size_t *length, > loff_t *ppos) > { > - char saved_string[NUMA_ZONELIST_ORDER_LEN]; > + char *str; > int ret; > - static DEFINE_MUTEX(zl_order_mutex); > > - mutex_lock(&zl_order_mutex); > - if (write) { > - if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) { > - ret = -EINVAL; > - goto out; > - } > - strcpy(saved_string, (char *)table->data); > + if (!write) { > + int len = sizeof("Default"); > + if (copy_to_user(buffer, "Default", len)) > + return -EFAULT; > + return len; > } That should to be "default" because the original code would have the proc entry display "default" unless it was set at runtime. Pretty weird I know but it's always possible someone is parsing the original default and not handling it properly. Otherwise I think we're way past the point where large memory 32-bit NUMA machines are a thing so Acked-by: Mel Gorman -- Mel Gorman SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: Re: [PATCH 1/9] mm, page_alloc: rip out ZONELIST_ORDER_ZONE Date: Fri, 14 Jul 2017 10:36:50 +0100 Message-ID: <20170714093650.l67vbem2g4typkta@suse.de> References: <20170714080006.7250-1-mhocko@kernel.org> <20170714080006.7250-2-mhocko@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Return-path: Content-Disposition: inline In-Reply-To: <20170714080006.7250-2-mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Michal Hocko Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andrew Morton , Johannes Weiner , Vlastimil Babka , LKML , Michal Hocko , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On Fri, Jul 14, 2017 at 09:59:58AM +0200, Michal Hocko wrote: > From: Michal Hocko > > Supporting zone ordered zonelists costs us just a lot of code while > the usefulness is arguable if existent at all. Mel has already made > node ordering default on 64b systems. 32b systems are still using > ZONELIST_ORDER_ZONE because it is considered better to fallback to > a different NUMA node rather than consume precious lowmem zones. > > This argument is, however, weaken by the fact that the memory reclaim > has been reworked to be node rather than zone oriented. This means > that lowmem requests have to skip over all highmem pages on LRUs already > and so zone ordering doesn't save the reclaim time much. So the only > advantage of the zone ordering is under a light memory pressure when > highmem requests do not ever hit into lowmem zones and the lowmem > pressure doesn't need to reclaim. > > Considering that 32b NUMA systems are rather suboptimal already and > it is generally advisable to use 64b kernel on such a HW I believe we > should rather care about the code maintainability and just get rid of > ZONELIST_ORDER_ZONE altogether. Keep systcl in place and warn if > somebody tries to set zone ordering either from kernel command line > or the sysctl. > > Cc: > Signed-off-by: Michal Hocko > index 80e4adb4c360..d9f4ea057e74 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4864,40 +4824,22 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write, > void __user *buffer, size_t *length, > loff_t *ppos) > { > - char saved_string[NUMA_ZONELIST_ORDER_LEN]; > + char *str; > int ret; > - static DEFINE_MUTEX(zl_order_mutex); > > - mutex_lock(&zl_order_mutex); > - if (write) { > - if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) { > - ret = -EINVAL; > - goto out; > - } > - strcpy(saved_string, (char *)table->data); > + if (!write) { > + int len = sizeof("Default"); > + if (copy_to_user(buffer, "Default", len)) > + return -EFAULT; > + return len; > } That should to be "default" because the original code would have the proc entry display "default" unless it was set at runtime. Pretty weird I know but it's always possible someone is parsing the original default and not handling it properly. Otherwise I think we're way past the point where large memory 32-bit NUMA machines are a thing so Acked-by: Mel Gorman -- Mel Gorman SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 4E4B5440905 for ; Fri, 14 Jul 2017 05:36:54 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id b11so8389378wmh.0 for ; Fri, 14 Jul 2017 02:36:54 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 64si1823549wmc.171.2017.07.14.02.36.53 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 14 Jul 2017 02:36:53 -0700 (PDT) Date: Fri, 14 Jul 2017 10:36:50 +0100 From: Mel Gorman Subject: Re: [PATCH 1/9] mm, page_alloc: rip out ZONELIST_ORDER_ZONE Message-ID: <20170714093650.l67vbem2g4typkta@suse.de> References: <20170714080006.7250-1-mhocko@kernel.org> <20170714080006.7250-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170714080006.7250-2-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , Johannes Weiner , Vlastimil Babka , LKML , Michal Hocko , linux-api@vger.kernel.org On Fri, Jul 14, 2017 at 09:59:58AM +0200, Michal Hocko wrote: > From: Michal Hocko > > Supporting zone ordered zonelists costs us just a lot of code while > the usefulness is arguable if existent at all. Mel has already made > node ordering default on 64b systems. 32b systems are still using > ZONELIST_ORDER_ZONE because it is considered better to fallback to > a different NUMA node rather than consume precious lowmem zones. > > This argument is, however, weaken by the fact that the memory reclaim > has been reworked to be node rather than zone oriented. This means > that lowmem requests have to skip over all highmem pages on LRUs already > and so zone ordering doesn't save the reclaim time much. So the only > advantage of the zone ordering is under a light memory pressure when > highmem requests do not ever hit into lowmem zones and the lowmem > pressure doesn't need to reclaim. > > Considering that 32b NUMA systems are rather suboptimal already and > it is generally advisable to use 64b kernel on such a HW I believe we > should rather care about the code maintainability and just get rid of > ZONELIST_ORDER_ZONE altogether. Keep systcl in place and warn if > somebody tries to set zone ordering either from kernel command line > or the sysctl. > > Cc: > Signed-off-by: Michal Hocko > index 80e4adb4c360..d9f4ea057e74 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4864,40 +4824,22 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write, > void __user *buffer, size_t *length, > loff_t *ppos) > { > - char saved_string[NUMA_ZONELIST_ORDER_LEN]; > + char *str; > int ret; > - static DEFINE_MUTEX(zl_order_mutex); > > - mutex_lock(&zl_order_mutex); > - if (write) { > - if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) { > - ret = -EINVAL; > - goto out; > - } > - strcpy(saved_string, (char *)table->data); > + if (!write) { > + int len = sizeof("Default"); > + if (copy_to_user(buffer, "Default", len)) > + return -EFAULT; > + return len; > } That should to be "default" because the original code would have the proc entry display "default" unless it was set at runtime. Pretty weird I know but it's always possible someone is parsing the original default and not handling it properly. Otherwise I think we're way past the point where large memory 32-bit NUMA machines are a thing so Acked-by: Mel Gorman -- Mel Gorman SUSE Labs -- 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