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From: David Sharp <dhsharp@google.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>,
	Ingo Molnar <mingo@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Justin Teravest <teravest@google.com>,
	Laurent Chavey <chavey@google.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/6] trace: trace syscall in its handler not from ptrace handler
Date: Thu, 29 Mar 2012 15:44:41 -0700	[thread overview]
Message-ID: <CAJL_ektkRunH_FXL+VfPCZqyNvB3Ab4PNjwzF2_dORudr0a32g@mail.gmail.com> (raw)
In-Reply-To: <4F74B42F.3050100@zytor.com>

On Thu, Mar 29, 2012 at 12:12 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 03/29/2012 12:02 PM, Vaibhav Nagarnaik wrote:
>>
>> Thanks for the feedback. I had missed this added latency due to this
>> patch when tracing is disabled.
>>
>> To fix that, instead of a TIF flag, I am using a flag in the
>> current->trace bitmap. I check that flag before jumping to the tracing
>> function. That reduces the latency from 83 ns/call to 74 ns/call.
>>
>
> ANY increase to the fastpath is unacceptable, period.

I think the last 4 ns would probably be eliminated if we could figure
out how to call the inline function trace_sys_enter directly instead
of through the out-of-line wrapper we had to add to work around the
preprocessor magic.

  parent reply	other threads:[~2012-03-29 22:45 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-26 18:39 [PATCH 0/6] Enhance and speed up syscall tracing Vaibhav Nagarnaik
2012-03-26 18:39 ` [PATCH 1/6] trace: syscalls.h - cleanup and simplify SYSCALL_METADATA() Vaibhav Nagarnaik
2012-03-26 18:39 ` [PATCH 2/6] trace: add support for 32 bit compat syscalls on x86_64 Vaibhav Nagarnaik
2012-03-27  4:49   ` H. Peter Anvin
2012-03-28 21:10     ` Vaibhav Nagarnaik
2012-03-28 21:11       ` Vaibhav Nagarnaik
2012-03-28 23:00         ` Vaibhav Nagarnaik
2012-03-26 18:39 ` [PATCH 3/6] trace: Refactor ftrace syscall macros to make them more readable Vaibhav Nagarnaik
2012-03-26 18:39 ` [PATCH 4/6] trace: trace syscall in its handler not from ptrace handler Vaibhav Nagarnaik
2012-03-27  5:00   ` H. Peter Anvin
2012-03-28 18:23     ` Vaibhav Nagarnaik
2012-03-29  2:43       ` H. Peter Anvin
2012-03-29  2:59         ` Steven Rostedt
2012-03-29  3:15           ` H. Peter Anvin
2012-03-29  3:02         ` Vaibhav Nagarnaik
2012-03-29  3:16           ` H. Peter Anvin
2012-03-29  6:20           ` Ingo Molnar
2012-03-29 19:02             ` Vaibhav Nagarnaik
2012-03-29 19:12               ` H. Peter Anvin
2012-03-29 19:43                 ` Vaibhav Nagarnaik
2012-03-29 20:06                   ` H. Peter Anvin
2012-03-29 22:40                     ` David Sharp
2012-03-29 22:44                       ` H. Peter Anvin
2012-03-30 12:06                       ` Frederic Weisbecker
2012-03-30 11:57                     ` Frederic Weisbecker
2012-03-29 22:44                 ` David Sharp [this message]
2012-03-29 22:48                   ` H. Peter Anvin
2012-03-26 18:39 ` [PATCH 5/6] trace: raw_syscalls: Mark compat syscalls in the MSB of the syscall number Vaibhav Nagarnaik
2012-03-26 18:39 ` [PATCH 6/6] trace: get rid of the enabled_*_syscalls bitmaps Vaibhav Nagarnaik

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