All of lore.kernel.org
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	"Andy Lutomirski" <luto@kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
	"Rik van Riel" <riel@surriel.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v6] x86: load FPU registers on return to userland
Date: Wed, 13 Feb 2019 16:54:35 +0100	[thread overview]
Message-ID: <20190213155435.vnvgzu76ienzvfhv@linutronix.de> (raw)
In-Reply-To: <20190208131233.5g5guefglq6ik2ow@linutronix.de>

On 2019-02-08 14:12:33 [+0100], To Borislav Petkov wrote:
> Then we have lat_sig [0]. Without the series 64bit:
> |Signal handler overhead: 2.6839 microseconds
> |Signal handler overhead: 2.6996 microseconds
> |Signal handler overhead: 2.6821 microseconds
> 
> with the series:
> |Signal handler overhead: 3.2976 microseconds
> |Signal handler overhead: 3.3033 microseconds
> |Signal handler overhead: 3.2980 microseconds

Did a patch-by-patch run (64bit only, server preemption model, output in
us ("commit")):

2.368 ("Linux 5.0-rc5")

2.603 ("x86/fpu: Always store the registers in copy_fpstate_to_sigframe()")
  copy_fpstate_to_sigframe() stores to thread's FPU area and then copies
  user stack area.

2.668 ("x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD")
  this should be noise since preempt_disable/enable is a nop -
  test_thread_flag() isn't.

2.701 ("x86/fpu: Inline copy_user_to_fpregs_zeroing()")
  This pops up somehow but is simply code movement.

3.474 ("x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from kernel memory")
  This stands out. There a kmalloc() + saving to kernel memory + copy
  instead a direct save to kernel stack.

2.928 ("x86/fpu: Defer FPU state load until return to userspace")
  The kmalloc() has been removed. Just "copy-to-kernel-memory" and
  copy_to_user() remained.

So this looks like 0.3us for the save-copy + 0.3us for copy-restore. The
numbers for the preempt/low-lat-desktop have the same two spikes and
drop at the end.

Sebastian

      reply	other threads:[~2019-02-13 15:54 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 11:47 [PATCH v6] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 01/22] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() Sebastian Andrzej Siewior
2019-01-14 16:24   ` Borislav Petkov
2019-02-05 10:08     ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 02/22] x86/fpu: Remove fpu__restore() Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 03/22] x86/fpu: Remove preempt_disable() in fpu__clear() Sebastian Andrzej Siewior
2019-01-14 18:55   ` Borislav Petkov
2019-01-09 11:47 ` [PATCH 04/22] x86/fpu: Always init the `state' " Sebastian Andrzej Siewior
2019-01-14 19:32   ` Borislav Petkov
2019-01-09 11:47 ` [PATCH 05/22] x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2019-01-16 19:36   ` Borislav Petkov
2019-01-16 22:40     ` Sebastian Andrzej Siewior
2019-01-17 12:22       ` Borislav Petkov
2019-01-18 21:14         ` Sebastian Andrzej Siewior
2019-01-18 21:17           ` Dave Hansen
2019-01-18 21:37             ` Sebastian Andrzej Siewior
2019-01-18 21:43               ` Dave Hansen
2019-01-21 11:21             ` Oleg Nesterov
2019-01-22 13:40               ` Borislav Petkov
2019-01-22 16:15                 ` Oleg Nesterov
2019-01-22 17:00                   ` Borislav Petkov
2019-02-05 11:34                     ` Sebastian Andrzej Siewior
2019-02-05 11:17               ` Sebastian Andrzej Siewior
2019-02-26 16:38                 ` Oleg Nesterov
2019-03-08 18:12                   ` Sebastian Andrzej Siewior
2019-02-05 14:37         ` [PATCH 05/22 v2] " Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 06/22] x86/fpu: Don't save fxregs for ia32 frames " Sebastian Andrzej Siewior
2019-01-24 11:17   ` Borislav Petkov
2019-02-05 16:43     ` [PATCH 06/22 v2] x86/fpu: Don't save fxregs for ia32 frames in Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 07/22] x86/fpu: Remove fpu->initialized Sebastian Andrzej Siewior
2019-01-24 13:34   ` Borislav Petkov
2019-02-05 18:03     ` Sebastian Andrzej Siewior
2019-02-06 14:01       ` Borislav Petkov
2019-02-07 10:13         ` Sebastian Andrzej Siewior
2019-02-07 10:37           ` Borislav Petkov
2019-02-05 18:06     ` [PATCH 07/22 v2] " Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 08/22] x86/fpu: Remove user_fpu_begin() Sebastian Andrzej Siewior
2019-01-25 15:18   ` Borislav Petkov
2019-02-05 18:16     ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 09/22] x86/fpu: Add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2019-01-28 18:23   ` Borislav Petkov
2019-02-07 10:43     ` Sebastian Andrzej Siewior
2019-02-13  9:30       ` Borislav Petkov
2019-02-14 14:51         ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 10/22] x86/fpu: Make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2019-01-28 18:30   ` Borislav Petkov
2019-01-09 11:47 ` [PATCH 11/22] x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() " Sebastian Andrzej Siewior
2019-01-28 18:49   ` Borislav Petkov
2019-02-07 11:13     ` Sebastian Andrzej Siewior
2019-02-13  9:31       ` Borislav Petkov
2019-01-09 11:47 ` [PATCH 12/22] x86/fpu: Only write PKRU if it is different from current Sebastian Andrzej Siewior
2019-01-23 18:09   ` Dave Hansen
2019-02-07 11:27     ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 13/22] x86/pkeys: Don't check if PKRU is zero before writting it Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 14/22] x86/fpu: Eager switch PKRU state Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 15/22] x86/entry: Add TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2019-01-30 11:55   ` Borislav Petkov
2019-02-07 11:49     ` Sebastian Andrzej Siewior
2019-02-13  9:35       ` Borislav Petkov
2019-02-14 15:28         ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 16/22] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2019-01-30 11:43   ` Borislav Petkov
2019-02-07 13:28     ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 17/22] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2019-01-30 11:56   ` Borislav Petkov
2019-01-30 12:28     ` Sebastian Andrzej Siewior
2019-01-30 12:53       ` Borislav Petkov
2019-02-07 14:10         ` Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 18/22] x86/fpu: Update xstate's PKRU value on write_pkru() Sebastian Andrzej Siewior
2019-01-23 17:28   ` Dave Hansen
2019-01-09 11:47 ` [PATCH 19/22] x86/fpu: Inline copy_user_to_fpregs_zeroing() Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 20/22] x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from kernel memory Sebastian Andrzej Siewior
2019-01-30 21:29   ` Borislav Petkov
2019-01-09 11:47 ` [PATCH 21/22] x86/fpu: Merge the two code paths in __fpu__restore_sig() Sebastian Andrzej Siewior
2019-01-09 11:47 ` [PATCH 22/22] x86/fpu: Defer FPU state load until return to userspace Sebastian Andrzej Siewior
2019-01-31  9:16   ` Borislav Petkov
2019-01-15 12:44 ` [PATCH v6] x86: load FPU registers on return to userland David Laight
2019-01-15 13:15   ` 'Sebastian Andrzej Siewior'
2019-01-15 14:33     ` David Laight
2019-01-15 19:46   ` Dave Hansen
2019-01-15 20:26     ` Andy Lutomirski
2019-01-15 20:54       ` Dave Hansen
2019-01-15 21:11         ` Andy Lutomirski
2019-01-16 10:31           ` David Laight
2019-01-16 10:18       ` David Laight
2019-01-30 11:35 ` Borislav Petkov
2019-01-30 12:06   ` Sebastian Andrzej Siewior
2019-01-30 12:27     ` Borislav Petkov
2019-02-08 13:12       ` Sebastian Andrzej Siewior
2019-02-13 15:54         ` Sebastian Andrzej Siewior [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190213155435.vnvgzu76ienzvfhv@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=Jason@zx2c4.com \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=pbonzini@redhat.com \
    --cc=riel@surriel.com \
    --cc=rkrcmar@redhat.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.