From owner-freebsd-arch@freebsd.org  Thu Nov 26 07:36:50 2015
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 id 1a1r1v-000GOI-8u; Thu, 26 Nov 2015 09:31:47 +0200
Subject: Re: zero-cost SDT probes
To: Mark Johnston <markj@FreeBSD.org>,
 Konstantin Belousov <kostikbel@gmail.com>
References: <20151122024542.GA44664@wkstn-mjohnston.west.isilon.com>
 <20151123113511.GX58629@kib.kiev.ua>
 <20151125001136.GB70878@wkstn-mjohnston.west.isilon.com>
 <20151125131533.GB3448@kib.kiev.ua>
 <20151125232524.GB67865@wkstn-mjohnston.west.isilon.com>
Cc: freebsd-arch@FreeBSD.org
From: Andriy Gapon <avg@FreeBSD.org>
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Date: Thu, 26 Nov 2015 09:30:51 +0200
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On 26/11/2015 01:25, Mark Johnston wrote:
> On Wed, Nov 25, 2015 at 03:15:33PM +0200, Konstantin Belousov wrote:
>> Several variations of the approach allow to control each probe site
>> individually, while still avoiding jumps and reducing the cache consumption.
>> And, of course, the biggest advantage is avoiding the need to change the
>> text at runtime.
[snip]
> I see. I think this could be made to work, but there's still the
> complication of passing arguments to the probe. Copying them into some
> block in curthread is one way to do this, but it seems more expensive
> than the standard calling convention on amd64 at least.

Besides, the FBT probes are not going anywhere and they require the run-time
text modification.

-- 
Andriy Gapon