From: "H. Peter Anvin" <hpa@zytor.com>
To: "Xin, Xiaohui" <xiaohui.xin@intel.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Chuck Ebbert <cebbert@redhat.com>, Ingo Molnar <mingo@elte.hu>,
"Li, Xin" <xin.li@intel.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
Nick Piggin <npiggin@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Xen-devel <xen-devel@lists.xensource.com>
Subject: Re: Performance overhead of paravirt_ops on native identified
Date: Thu, 21 May 2009 20:39:01 -0700 [thread overview]
Message-ID: <4A161E55.4040401@zytor.com> (raw)
In-Reply-To: <C85CEDA13AB1CF4D9D597824A86D2B9005760A96DA@PDSMSX501.ccr.corp.intel.com>
Xin, Xiaohui wrote:
> Remember we have done one experiment with "jump", the result shows seems the overhead is even more than the call.
I didn't, no. That seems extremely weird to me.
(Unbalancing the call/ret stack is known to suck royally, of course.)
>>>
>>>
>> Can't those calls be changed to jumps?
>>
>
> In this specific instance of this example, yes. But if you start
> enabling various spinlock debug options then there'll be code following
> the call. It would be hard for the runtime patching machinery to know
> when it would be safe to do the substitution.
>
When there is code after the call, it's rather obviously not safe.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: "Xin, Xiaohui" <xiaohui.xin@intel.com>
Cc: Nick Piggin <npiggin@suse.de>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Xen-devel <xen-devel@lists.xensource.com>,
Chuck Ebbert <cebbert@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Li, Xin" <xin.li@intel.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: Performance overhead of paravirt_ops on native identified
Date: Thu, 21 May 2009 20:39:01 -0700 [thread overview]
Message-ID: <4A161E55.4040401@zytor.com> (raw)
In-Reply-To: <C85CEDA13AB1CF4D9D597824A86D2B9005760A96DA@PDSMSX501.ccr.corp.intel.com>
Xin, Xiaohui wrote:
> Remember we have done one experiment with "jump", the result shows seems the overhead is even more than the call.
I didn't, no. That seems extremely weird to me.
(Unbalancing the call/ret stack is known to suck royally, of course.)
>>>
>>>
>> Can't those calls be changed to jumps?
>>
>
> In this specific instance of this example, yes. But if you start
> enabling various spinlock debug options then there'll be code following
> the call. It would be hard for the runtime patching machinery to know
> when it would be safe to do the substitution.
>
When there is code after the call, it's rather obviously not safe.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-05-22 3:39 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-14 0:16 Performance overhead of paravirt_ops on native identified Jeremy Fitzhardinge
2009-05-14 0:16 ` Jeremy Fitzhardinge
2009-05-14 1:10 ` H. Peter Anvin
2009-05-14 1:10 ` H. Peter Anvin
2009-05-14 8:25 ` Peter Zijlstra
2009-05-14 8:25 ` Peter Zijlstra
2009-05-14 14:05 ` H. Peter Anvin
2009-05-14 14:05 ` H. Peter Anvin
2009-05-14 17:36 ` Jeremy Fitzhardinge
2009-05-14 17:36 ` Jeremy Fitzhardinge
2009-05-14 17:50 ` H. Peter Anvin
2009-05-14 17:50 ` H. Peter Anvin
2009-05-14 8:05 ` [Xen-devel] Performance overhead of paravirt_ops on nativeidentified Jan Beulich
2009-05-14 8:05 ` Jan Beulich
2009-05-14 8:33 ` [Xen-devel] " Peter Zijlstra
2009-05-14 17:45 ` Jeremy Fitzhardinge
2009-05-14 17:45 ` Jeremy Fitzhardinge
2009-05-15 8:10 ` [Xen-devel] " Jan Beulich
2009-05-15 18:50 ` Jeremy Fitzhardinge
2009-05-18 7:19 ` Jan Beulich
2009-05-18 7:19 ` Jan Beulich
2009-05-20 22:42 ` [Xen-devel] " Jeremy Fitzhardinge
2009-05-20 22:42 ` Jeremy Fitzhardinge
2009-05-15 18:18 ` [tip:x86/urgent] x86: Fix performance regression caused by paravirt_ops on native kernels tip-bot for Jeremy Fitzhardinge
2009-05-15 18:18 ` tip-bot for Jeremy Fitzhardinge
2009-05-21 22:42 ` Performance overhead of paravirt_ops on native identified Chuck Ebbert
2009-05-21 22:48 ` Jeremy Fitzhardinge
2009-05-21 22:48 ` Jeremy Fitzhardinge
2009-05-21 23:10 ` H. Peter Anvin
2009-05-21 23:10 ` H. Peter Anvin
2009-05-22 1:26 ` Xin, Xiaohui
2009-05-22 1:26 ` Xin, Xiaohui
2009-05-22 3:39 ` H. Peter Anvin [this message]
2009-05-22 3:39 ` H. Peter Anvin
2009-05-22 4:27 ` Jeremy Fitzhardinge
2009-05-22 4:27 ` Jeremy Fitzhardinge
2009-05-22 5:59 ` Xin, Xiaohui
2009-05-22 5:59 ` Xin, Xiaohui
2009-05-22 16:33 ` H. Peter Anvin
2009-05-22 16:33 ` H. Peter Anvin
2009-05-22 22:44 ` Jeremy Fitzhardinge
2009-05-22 22:44 ` Jeremy Fitzhardinge
2009-05-22 22:47 ` H. Peter Anvin
2009-05-22 22:47 ` H. Peter Anvin
2009-05-25 9:15 ` [benchmark] 1% performance overhead of paravirt_ops on native kernels Ingo Molnar
2009-05-26 18:42 ` Jeremy Fitzhardinge
2009-05-28 6:17 ` Nick Piggin
2009-05-28 20:57 ` Jeremy Fitzhardinge
2009-05-30 10:23 ` Ingo Molnar
2009-06-02 14:18 ` Chris Mason
2009-06-02 14:49 ` Ulrich Drepper
2009-06-02 15:03 ` Chris Mason
2009-06-02 15:22 ` Ulrich Drepper
2009-06-02 16:20 ` Chris Mason
2009-06-02 18:13 ` Pekka Enberg
2009-06-02 18:06 ` Pekka Enberg
2009-06-02 18:27 ` Chris Mason
2009-06-03 6:33 ` Jeremy Fitzhardinge
2009-06-02 19:14 ` Thomas Gleixner
2009-06-02 19:51 ` Chris Mason
2009-06-03 12:38 ` Rusty Russell
2009-06-03 16:09 ` Linus Torvalds
[not found] ` <200906041554.37102.rusty@rustcorp.com.au>
2009-06-04 15:02 ` Linus Torvalds
2009-06-04 21:52 ` Dave McCracken
2009-06-05 7:31 ` Gerd Hoffmann
2009-06-05 14:31 ` Rusty Russell
2009-06-06 18:54 ` Anders K. Pedersen
2009-06-05 4:46 ` Rusty Russell
2009-06-05 14:54 ` Linus Torvalds
2009-06-07 0:53 ` Rusty Russell
2009-06-08 14:53 ` Linus Torvalds
2009-06-09 9:39 ` Nick Piggin
2009-06-09 11:17 ` Ingo Molnar
2009-06-09 12:10 ` Nick Piggin
2009-06-09 12:25 ` Ingo Molnar
2009-06-09 12:42 ` Nick Piggin
2009-06-09 12:56 ` Avi Kivity
2009-06-09 15:18 ` Linus Torvalds
2009-06-09 23:33 ` Paul Mackerras
2009-06-10 1:26 ` Ingo Molnar
2009-06-09 15:07 ` Linus Torvalds
2009-06-09 15:09 ` H. Peter Anvin
2009-06-09 18:06 ` Linus Torvalds
2009-06-09 18:07 ` Linus Torvalds
2009-06-09 22:48 ` Matthew Garrett
2009-06-09 22:54 ` H. Peter Anvin
2009-06-09 14:54 ` Linus Torvalds
2009-06-09 14:57 ` Ingo Molnar
2009-06-09 15:55 ` Avi Kivity
2009-06-09 15:38 ` Nick Piggin
2009-06-09 16:00 ` Linus Torvalds
2009-06-09 16:21 ` Nick Piggin
2009-06-09 16:26 ` Linus Torvalds
2009-06-09 16:45 ` Nick Piggin
2009-06-09 17:08 ` Linus Torvalds
2009-06-10 5:53 ` Nick Piggin
2009-06-17 9:40 ` Pavel Machek
2009-06-17 9:56 ` Nick Piggin
2009-06-10 6:29 ` Peter Zijlstra
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