Re: [PATCH v3 0/7] x86: Rewrite switch_to()

From	Herbert Xu <herbert@gondor.apana.org.au>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 0/7] x86: Rewrite switch_to()
Date	2016-08-17 07:20 +0200
Message-ID	<s71qF-4Z2-3@gated-at.bofh.it> (permalink)
References	<s61Cs-7hw-73@gated-at.bofh.it>
Organization	Core

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Andy Lutomirski <luto@amacapital.net> wrote:
>
> I will be quite surprised if you can measure any effect at all.  I've
> never seen context switches take fewer than ~2k cycles, and on my
> laptop, they take 8k-9k cycles.  The scheduler is really, really slow.

Indeed, I think I still have a bugzilla entry somewhere regarding
the huge performance regression when we first switched over to the
current scheduler.

Over the years people have been trying to hack around it, e.g.,
network driver polling, low latency socket, anything to avoid
going into the scheduler.  We really should fix it properly some
day.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Thread

[PATCH v3 0/7] x86: Rewrite switch_to() Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:40 +0200
  [PATCH v3 1/7] x86-32, kgdb: Don't use thread.ip in sleeping_thread_to_gdb_regs() Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:40 +0200
    [tip:x86/asm] sched/x86/32, kgdb: Don't use thread.ip in  sleeping_thread_to_gdb_regs() tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:50 +0200
  [PATCH v3 7/7] Revert "sched: Mark __schedule() stack frame as non-standard" Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:40 +0200
    [tip:x86/asm] sched: Remove __schedule() non-standard frame  annotation tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:50 +0200
  [PATCH v3 2/7] x86-64, kgdb: clear GDB_PS on 64-bit Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:40 +0200
    [tip:x86/asm] sched/x86/64, kgdb: Clear GDB_PS on 64-bit tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:50 +0200
  [PATCH v3 3/7] x86: Add struct inactive_task_frame Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:40 +0200
    [tip:x86/asm] sched/x86: Add 'struct inactive_task_frame' to better  document the sleeping task stack frame tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:20 +0200
  [PATCH v3 4/7] x86: Rewrite switch_to() code Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:50 +0200
    [tip:x86/asm] sched/x86: Rewrite the switch_to() code tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:20 +0200
  [PATCH v3 6/7] x86: Fix thread_saved_pc() Brian Gerst <brgerst@gmail.com> - 2016-08-13 18:50 +0200
    [tip:x86/asm] sched/x86: Fix thread_saved_pc() tip-bot for Brian Gerst <tipbot@zytor.com> - 2016-08-24 15:20 +0200
  Re: [PATCH v3 0/7] x86: Rewrite switch_to() Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-13 19:20 +0200
    Re: [PATCH v3 0/7] x86: Rewrite switch_to() Ingo Molnar <mingo@kernel.org> - 2016-08-14 10:30 +0200
      Re: [PATCH v3 0/7] x86: Rewrite switch_to() Andy Lutomirski <luto@amacapital.net> - 2016-08-14 13:20 +0200
        Re: [PATCH v3 0/7] x86: Rewrite switch_to() Herbert Xu <herbert@gondor.apana.org.au> - 2016-08-17 07:20 +0200
      Re: [PATCH v3 0/7] x86: Rewrite switch_to() Brian Gerst <brgerst@gmail.com> - 2016-08-14 16:20 +0200
        Re: [PATCH v3 0/7] x86: Rewrite switch_to() Ingo Molnar <mingo@kernel.org> - 2016-08-15 07:20 +0200
          Re: [PATCH v3 0/7] x86: Rewrite switch_to() Brian Gerst <brgerst@gmail.com> - 2016-08-15 13:50 +0200
          Re: [PATCH v3 0/7] x86: Rewrite switch_to() Andy Lutomirski <luto@amacapital.net> - 2016-08-17 23:30 +0200
    Re: [PATCH v3 0/7] x86: Rewrite switch_to() Brian Gerst <brgerst@gmail.com> - 2016-08-14 12:30 +0200
  Re: [PATCH v3 0/7] x86: Rewrite switch_to() Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-17 23:30 +0200

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