Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-04 Thread Will Deacon
Hi Steve, [adding linux-mm, since this has turned into a discussion about THP splitting] On Fri, Oct 04, 2013 at 11:31:42AM +0100, Steve Capper wrote: > On Thu, Oct 03, 2013 at 11:07:44AM -0700, Zi Shen Lim wrote: > > On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon wrote: > > > On Thu, Oct 03,

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-04 Thread Steve Capper
On Thu, Oct 03, 2013 at 11:07:44AM -0700, Zi Shen Lim wrote: > Thanks for your feedback Will. > > On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon wrote: > > On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: > >> Futex uses GUP. Currently on ARM, the default __get_user_pages_fast > >>

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-04 Thread Steve Capper
On Thu, Oct 03, 2013 at 11:07:44AM -0700, Zi Shen Lim wrote: Thanks for your feedback Will. On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon will.dea...@arm.com wrote: On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: Futex uses GUP. Currently on ARM, the default

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-04 Thread Will Deacon
Hi Steve, [adding linux-mm, since this has turned into a discussion about THP splitting] On Fri, Oct 04, 2013 at 11:31:42AM +0100, Steve Capper wrote: On Thu, Oct 03, 2013 at 11:07:44AM -0700, Zi Shen Lim wrote: On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon will.dea...@arm.com wrote: On

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Zi Shen Lim
Thanks for your feedback Will. On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon wrote: > On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: >> Futex uses GUP. Currently on ARM, the default __get_user_pages_fast >> being used always returns 0, leading to a forever loop in get_futex_key :(

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Will Deacon
On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: > Futex uses GUP. Currently on ARM, the default __get_user_pages_fast > being used always returns 0, leading to a forever loop in get_futex_key :( > > Implementing GUP solves this problem. > > Tested on vexpress-A15 on QEMU. >

[RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Zi Shen Lim
Futex uses GUP. Currently on ARM, the default __get_user_pages_fast being used always returns 0, leading to a forever loop in get_futex_key :( Implementing GUP solves this problem. Tested on vexpress-A15 on QEMU. 8<>8 Implement

[RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Zi Shen Lim
Futex uses GUP. Currently on ARM, the default __get_user_pages_fast being used always returns 0, leading to a forever loop in get_futex_key :( Implementing GUP solves this problem. Tested on vexpress-A15 on QEMU. 88 Implement

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Will Deacon
On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: Futex uses GUP. Currently on ARM, the default __get_user_pages_fast being used always returns 0, leading to a forever loop in get_futex_key :( Implementing GUP solves this problem. Tested on vexpress-A15 on QEMU.

Re: [RFC] ARM: lockless get_user_pages_fast()

2013-10-03 Thread Zi Shen Lim
Thanks for your feedback Will. On Thu, Oct 3, 2013 at 10:27 AM, Will Deacon will.dea...@arm.com wrote: On Thu, Oct 03, 2013 at 06:15:15PM +0100, Zi Shen Lim wrote: Futex uses GUP. Currently on ARM, the default __get_user_pages_fast being used always returns 0, leading to a forever loop in