Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1727958

Re: [RFC 00/17] Pile o' entry stack changes

Show all headers | View raw

* Andy Lutomirski <luto@kernel.org> wrote:

> On Wed, Sep 6, 2017 at 3:16 PM, Andi Kleen <andi@firstfloor.org> wrote:
> > Andy Lutomirski <luto@kernel.org> writes:
> >>
> >>  - Lots of people (Linus included) have asked to convert the entry
> >>    code to pop registers on exit instead of movqing them off the
> >>    stack.  This makes a bunch of progress in that direction.
> >
> > You should benchmark it on Atoms. Likely it's a regression there
> > because they don't have the special PUSH/POP acceleration.
> 
> I'm not entirely sure this is a worthwhile reason.  Atom will lose a
> few cycles due to POP throughput, but there's a lot less decode
> bandwidth needed and we save a cache line or two.

I think we can also safely assume that Atom will eventually either join the
21st century or die out - mild Atom micro-costs are not a good reason to
complicate the entry code...

Thanks,

	Ingo

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[RFC 00/17] Pile o' entry stack changes Andy Lutomirski <luto@kernel.org> - 2017-09-06 23:50 +0200
  [RFC 04/17] x86/asm/64: Simplify reg restore code in the standard IRET paths Andy Lutomirski <luto@kernel.org> - 2017-09-06 23:50 +0200
  [RFC 03/17] x86/asm/64: Move SWAPGS into the common iret-to-usermode path Andy Lutomirski <luto@kernel.org> - 2017-09-06 23:50 +0200
  [RFC 02/17] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Andy Lutomirski <luto@kernel.org> - 2017-09-06 23:50 +0200
  Re: [RFC 00/17] Pile o' entry stack changes Andi Kleen <andi@firstfloor.org> - 2017-09-07 00:20 +0200
    Re: [RFC 00/17] Pile o' entry stack changes Andy Lutomirski <luto@kernel.org> - 2017-09-07 02:10 +0200
      Re: [RFC 00/17] Pile o' entry stack changes Ingo Molnar <mingo@kernel.org> - 2017-09-07 09:10 +0200

csiph-web