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 fo

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 measu

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 i

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 RF