Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Peter Zijlstra
On Wed, Sep 10, 2014 at 11:27:44AM -0700, Andi Kleen wrote: > > Note that since then we have actually fixed the 'cannot fault from NMI > > context' thing, so we should be able to actually take those faults. I > > suspect we can simply remove those WARNs from the vmalloc fault path, > > but it would

Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Andi Kleen
> Note that since then we have actually fixed the 'cannot fault from NMI > context' thing, so we should be able to actually take those faults. I > suspect we can simply remove those WARNs from the vmalloc fault path, > but it would need double checking to see if there's no other reasons. I think w

Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Peter Zijlstra
On Wed, Sep 10, 2014 at 06:35:56PM +0200, Peter Zijlstra wrote: > On Wed, Sep 10, 2014 at 04:40:12PM +0200, Andi Kleen wrote: > > > We did this once, and that blew up big time. > > > > > > Even now, vmalloc_fault() has a very explicit: > > > > > > WARN_ON_ONCE(in_nmi()); > > > > > > So this is

Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Peter Zijlstra
On Wed, Sep 10, 2014 at 04:40:12PM +0200, Andi Kleen wrote: > > We did this once, and that blew up big time. > > > > Even now, vmalloc_fault() has a very explicit: > > > > WARN_ON_ONCE(in_nmi()); > > > > So this isn't going to happen until you fix that. > > Good point. > > We just need to ca

Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Andi Kleen
> We did this once, and that blew up big time. > > Even now, vmalloc_fault() has a very explicit: > > WARN_ON_ONCE(in_nmi()); > > So this isn't going to happen until you fix that. Good point. We just need to call vmalloc_sync_all at allocation time, no need to change vmalloc_fault. -Andi

Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-10 Thread Peter Zijlstra
On Tue, Sep 09, 2014 at 05:03:21PM -0700, Andi Kleen wrote: > From: Andi Kleen > > On my workstation the order 4 BTS buffer allocation fails regularly > after the system has been up for some time due to memory > fragmentation. > > BTS is virtual memory, so we can just fall back to vmalloc > inst

[PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

2014-09-09 Thread Andi Kleen
From: Andi Kleen On my workstation the order 4 BTS buffer allocation fails regularly after the system has been up for some time due to memory fragmentation. BTS is virtual memory, so we can just fall back to vmalloc instead of failing. Do this here. Signed-off-by: Andi Kleen --- arch/x86/ker