Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-04-04 Thread Andy Lutomirski
On Tue, Mar 31, 2015 at 8:59 AM, Denys Vlasenko wrote: > On 03/31/2015 03:54 PM, Andy Lutomirski wrote: >> On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko wrote: >>> This is not proposed to be merged yet. >>> >>> Andy, this patch is in spirit of your crazy ideas of repurposing >>> instructions

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-04-04 Thread Andy Lutomirski
On Tue, Mar 31, 2015 at 8:59 AM, Denys Vlasenko dvlas...@redhat.com wrote: On 03/31/2015 03:54 PM, Andy Lutomirski wrote: On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko dvlas...@redhat.com wrote: This is not proposed to be merged yet. Andy, this patch is in spirit of your crazy ideas of

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Denys Vlasenko
On 03/31/2015 03:54 PM, Andy Lutomirski wrote: > On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko wrote: >> This is not proposed to be merged yet. >> >> Andy, this patch is in spirit of your crazy ideas of repurposing >> instructions for the roles they weren't intended for :) >> >> Recently I

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Andy Lutomirski
On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko wrote: > This is not proposed to be merged yet. > > Andy, this patch is in spirit of your crazy ideas of repurposing > instructions for the roles they weren't intended for :) > > Recently I measured IRET timings and was newly "impressed" > how slow

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Steven Rostedt
On Tue, 31 Mar 2015 14:46:21 +0200 Denys Vlasenko wrote: > @@ -750,6 +750,53 @@ retint_kernel: >* The iretq could re-enable interrupts: >*/ > TRACE_IRQS_IRETQ > + > + /* > + * Since we return to kernel, CS and SS do not need changing. > + * Only RSP, RIP and

[RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Denys Vlasenko
This is not proposed to be merged yet. Andy, this patch is in spirit of your crazy ideas of repurposing instructions for the roles they weren't intended for :) Recently I measured IRET timings and was newly "impressed" how slow it is. 200+ cycles. So I started thinking... When we return from

[RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Denys Vlasenko
This is not proposed to be merged yet. Andy, this patch is in spirit of your crazy ideas of repurposing instructions for the roles they weren't intended for :) Recently I measured IRET timings and was newly impressed how slow it is. 200+ cycles. So I started thinking... When we return from

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Steven Rostedt
On Tue, 31 Mar 2015 14:46:21 +0200 Denys Vlasenko dvlas...@redhat.com wrote: @@ -750,6 +750,53 @@ retint_kernel: * The iretq could re-enable interrupts: */ TRACE_IRQS_IRETQ + + /* + * Since we return to kernel, CS and SS do not need changing. + * Only

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Andy Lutomirski
On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko dvlas...@redhat.com wrote: This is not proposed to be merged yet. Andy, this patch is in spirit of your crazy ideas of repurposing instructions for the roles they weren't intended for :) Recently I measured IRET timings and was newly impressed

Re: [RFC PATCH] x86: optimize IRET returns to kernel

2015-03-31 Thread Denys Vlasenko
On 03/31/2015 03:54 PM, Andy Lutomirski wrote: On Tue, Mar 31, 2015 at 5:46 AM, Denys Vlasenko dvlas...@redhat.com wrote: This is not proposed to be merged yet. Andy, this patch is in spirit of your crazy ideas of repurposing instructions for the roles they weren't intended for :) Recently