From: fche@redhat.com (Frank Ch. Eigler)
To: Mark Wielaard <mjw@redhat.com>
Cc: Roland McGrath <roland@redhat.com>, Stan Cox <scox@redhat.com>,
systemtap@sourceware.org
Subject: Re: new static user probe types
Date: Thu, 23 Jul 2009 14:40:00 -0000 [thread overview]
Message-ID: <y0m3a8n1mzp.fsf@fche.csb> (raw)
In-Reply-To: <1248344916.3494.33.camel@springer.wildebeest.org> (Mark Wielaard's message of "Thu, 23 Jul 2009 12:28:36 +0200")
Mark Wielaard <mjw@redhat.com> writes:
> [...]
>> The point of this is to skip any argument-packing work generated by the
>> compiler, which would be inside the "if unlikely" block, right?
(Yes.)
> Partly, but it is sadly not guaranteed by GCC.
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40207
Note that this was for an implementation that relies on static inline
functions. Pure macros are OK.
>> I think this is a lot like some things Mathieu already experimented with
>> and measured in the kernel context. I think he pursued a code-patching
>> flavor that patched an immediate operand because that was measured as
>> faster than having the actual extra load of a simple enabled_p variable.
(Yes, and other tracing widgets from other OS's have discovered the
same thing. Of course that costs per-arch complications instead, thus
the simpler proposal as a first step.)
- FChE
next prev parent reply other threads:[~2009-07-23 14:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-26 21:26 Stan Cox
2009-07-15 16:19 ` Stan Cox
2009-07-15 18:39 ` Josh Stone
2009-07-15 20:47 ` Stan Cox
2009-07-15 21:57 ` Josh Stone
2009-07-16 13:44 ` Stan Cox
2009-07-20 18:34 ` Stan Cox
2009-07-22 10:42 ` Mark Wielaard
2009-07-22 14:39 ` Frank Ch. Eigler
2009-07-22 17:10 ` Mark Wielaard
2009-07-29 15:44 ` Stan Cox
2009-07-29 15:51 ` Stan Cox
2009-07-23 3:07 ` Roland McGrath
2009-07-23 10:28 ` Mark Wielaard
2009-07-23 14:40 ` Frank Ch. Eigler [this message]
2009-07-23 19:33 ` Roland McGrath
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