From: Lin Feng <linfeng@cn.fujitsu.com> To: Minchan Kim <minchan@kernel.org> Cc: akpm@linux-foundation.org, mgorman@suse.de, bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org, walken@google.com, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, rientjes@google.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, jiang.liu@huawei.com, linux-mm@kvack.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Date: Tue, 05 Feb 2013 12:42:48 +0800 [thread overview] Message-ID: <51108DC8.4090704@cn.fujitsu.com> (raw) In-Reply-To: <20130205005859.GE2610@blaptop> Hi Minchan, On 02/05/2013 08:58 AM, Minchan Kim wrote: > Hello, > > On Mon, Feb 04, 2013 at 06:04:06PM +0800, Lin Feng wrote: >> Currently get_user_pages() always tries to allocate pages from movable zone, >> as discussed in thread https://lkml.org/lkml/2012/11/29/69, in some case users >> of get_user_pages() is easy to pin user pages for a long time(for now we found >> that pages pinned as aio ring pages is such case), which is fatal for memory >> hotplug/remove framework. >> >> So the 1st patch introduces a new library function called >> get_user_pages_non_movable() to pin pages only from zone non-movable in memory. >> It's a wrapper of get_user_pages() but it makes sure that all pages come from >> non-movable zone via additional page migration. >> >> The 2nd patch gets around the aio ring pages can't be migrated bug caused by >> get_user_pages() via using the new function. It only works when configed with >> CONFIG_MEMORY_HOTREMOVE, otherwise it uses the old version of get_user_pages(). > > CMA has same issue but the problem is the driver developers or any subsystem > using GUP can't know their pages is in CMA area or not in advance. > So all of client of GUP should use GUP_NM to work them with CMA/MEMORY_HOTPLUG well? > Even some driver module in embedded side doesn't open their source code. Yes, it somehow depends on the users of GUP. In MEMORY_HOTPLUG case, as for most users of GUP, they will release the pinned pages immediately and to such users they should get a good performance, using the old style interface is a smart way. And we had better just deal with the cases we have to by using the new interface. > > I would like to make GUP smart so it allocates a page from non-movable/non-cma area > when memory-hotplug/cma is enabled(CONFIG_MIGRATE_ISOLATE). Yeb. it might hurt GUP > performance but it is just trade-off for using CMA/memory-hotplug, IMHO. :( As I debuged the get_user_pages(), I found that some pages is already there and may be allocated before we call get_user_pages(). __get_user_pages() have following logic to handle such case. 1786 while (!(page = follow_page(vma, start, foll_flags))) { 1787 int ret; To such case an additional alloc-flag or such doesn't work, it's difficult to keep GUP as smart as we want :( , so I worked out the migration approach to get around and avoid messing up the current code :) thanks, linfeng
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From: Lin Feng <linfeng@cn.fujitsu.com> To: Minchan Kim <minchan@kernel.org> Cc: akpm@linux-foundation.org, mgorman@suse.de, bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org, walken@google.com, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, rientjes@google.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, jiang.liu@huawei.com, linux-mm@kvack.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Date: Tue, 05 Feb 2013 12:42:48 +0800 [thread overview] Message-ID: <51108DC8.4090704@cn.fujitsu.com> (raw) In-Reply-To: <20130205005859.GE2610@blaptop> Hi Minchan, On 02/05/2013 08:58 AM, Minchan Kim wrote: > Hello, > > On Mon, Feb 04, 2013 at 06:04:06PM +0800, Lin Feng wrote: >> Currently get_user_pages() always tries to allocate pages from movable zone, >> as discussed in thread https://lkml.org/lkml/2012/11/29/69, in some case users >> of get_user_pages() is easy to pin user pages for a long time(for now we found >> that pages pinned as aio ring pages is such case), which is fatal for memory >> hotplug/remove framework. >> >> So the 1st patch introduces a new library function called >> get_user_pages_non_movable() to pin pages only from zone non-movable in memory. >> It's a wrapper of get_user_pages() but it makes sure that all pages come from >> non-movable zone via additional page migration. >> >> The 2nd patch gets around the aio ring pages can't be migrated bug caused by >> get_user_pages() via using the new function. It only works when configed with >> CONFIG_MEMORY_HOTREMOVE, otherwise it uses the old version of get_user_pages(). > > CMA has same issue but the problem is the driver developers or any subsystem > using GUP can't know their pages is in CMA area or not in advance. > So all of client of GUP should use GUP_NM to work them with CMA/MEMORY_HOTPLUG well? > Even some driver module in embedded side doesn't open their source code. Yes, it somehow depends on the users of GUP. In MEMORY_HOTPLUG case, as for most users of GUP, they will release the pinned pages immediately and to such users they should get a good performance, using the old style interface is a smart way. And we had better just deal with the cases we have to by using the new interface. > > I would like to make GUP smart so it allocates a page from non-movable/non-cma area > when memory-hotplug/cma is enabled(CONFIG_MIGRATE_ISOLATE). Yeb. it might hurt GUP > performance but it is just trade-off for using CMA/memory-hotplug, IMHO. :( As I debuged the get_user_pages(), I found that some pages is already there and may be allocated before we call get_user_pages(). __get_user_pages() have following logic to handle such case. 1786 while (!(page = follow_page(vma, start, foll_flags))) { 1787 int ret; To such case an additional alloc-flag or such doesn't work, it's difficult to keep GUP as smart as we want :( , so I worked out the migration approach to get around and avoid messing up the current code :) thanks, linfeng -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-02-05 4:44 UTC|newest] Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-02-04 10:04 [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Lin Feng 2013-02-04 10:04 ` Lin Feng 2013-02-04 10:04 ` [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable() Lin Feng 2013-02-04 10:04 ` Lin Feng 2013-02-04 10:04 ` Lin Feng 2013-02-05 0:06 ` Andrew Morton 2013-02-05 0:06 ` Andrew Morton 2013-02-05 0:06 ` Andrew Morton 2013-02-05 0:18 ` Andrew Morton 2013-02-05 0:18 ` Andrew Morton 2013-02-05 3:09 ` Lin Feng 2013-02-05 3:09 ` Lin Feng 2013-02-05 3:09 ` Lin Feng 2013-02-05 21:13 ` Andrew Morton 2013-02-05 21:13 ` Andrew Morton 2013-02-05 21:13 ` Andrew Morton 2013-02-05 11:57 ` Mel Gorman 2013-02-05 11:57 ` Mel Gorman 2013-02-05 11:57 ` Mel Gorman 2013-02-05 13:32 ` Mel Gorman 2013-02-05 13:32 ` Mel Gorman 2013-02-05 13:32 ` Mel Gorman 2013-02-19 13:37 ` Lin Feng 2013-02-19 13:37 ` Lin Feng 2013-02-20 2:34 ` Lin Feng 2013-02-20 2:34 ` Lin Feng 2013-02-20 2:34 ` Lin Feng 2013-02-20 2:44 ` Wanpeng Li 2013-02-20 2:44 ` Wanpeng Li 2013-02-20 2:44 ` Wanpeng Li 2013-02-20 2:59 ` Lin Feng 2013-02-20 2:59 ` Lin Feng 2013-02-20 9:58 ` Simon Jeons 2013-02-20 9:58 ` Simon Jeons 2013-02-20 10:23 ` Lin Feng 2013-02-20 10:23 ` Lin Feng 2013-02-20 10:23 ` Lin Feng 2013-02-20 11:31 ` Simon Jeons 2013-02-20 11:31 ` Simon Jeons 2013-02-20 11:54 ` Lin Feng 2013-02-20 11:54 ` Lin Feng 2013-02-20 11:54 ` Lin Feng 2013-02-06 2:26 ` Michel Lespinasse 2013-02-06 2:26 ` Michel Lespinasse 2013-02-06 2:26 ` Michel Lespinasse 2013-02-06 10:41 ` Mel Gorman 2013-02-06 10:41 ` Mel Gorman 2013-02-18 10:34 ` Lin Feng 2013-02-18 10:34 ` Lin Feng 2013-02-18 10:34 ` Lin Feng 2013-02-18 15:17 ` Mel Gorman 2013-02-18 15:17 ` Mel Gorman 2013-02-18 15:17 ` Mel Gorman 2013-02-19 9:55 ` Lin Feng 2013-02-19 9:55 ` Lin Feng 2013-02-19 10:34 ` Mel Gorman 2013-02-19 10:34 ` Mel Gorman 2013-02-19 10:34 ` Mel Gorman 2013-02-04 10:04 ` [PATCH 2/2] fs/aio.c: use get_user_pages_non_movable() to pin ring pages when support memory hotremove Lin Feng 2013-02-04 10:04 ` Lin Feng 2013-02-04 10:04 ` Lin Feng 2013-02-04 15:18 ` Jeff Moyer 2013-02-04 15:18 ` Jeff Moyer 2013-02-04 15:18 ` Jeff Moyer 2013-02-04 23:02 ` Zach Brown 2013-02-04 23:02 ` Zach Brown 2013-02-04 23:02 ` Zach Brown 2013-02-05 5:35 ` Lin Feng 2013-02-05 5:35 ` Lin Feng 2013-02-05 5:35 ` Lin Feng 2013-02-05 5:06 ` Lin Feng 2013-02-05 5:06 ` Lin Feng 2013-02-05 0:58 ` [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Minchan Kim 2013-02-05 0:58 ` Minchan Kim 2013-02-05 0:58 ` Minchan Kim 2013-02-05 4:42 ` Lin Feng [this message] 2013-02-05 4:42 ` Lin Feng 2013-02-05 5:25 ` Minchan Kim 2013-02-05 5:25 ` Minchan Kim 2013-02-05 5:25 ` Minchan Kim 2013-02-05 6:18 ` Lin Feng 2013-02-05 6:18 ` Lin Feng 2013-02-05 7:45 ` Minchan Kim 2013-02-05 7:45 ` Minchan Kim 2013-02-05 7:45 ` Minchan Kim 2013-02-05 8:27 ` Lin Feng 2013-02-05 8:27 ` Lin Feng 2013-02-05 8:27 ` Lin Feng
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