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Date: Mon, 18 Jan 2010 18:52:32 +0200
From: Avi Kivity <avi@redhat.com>
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To: ananth@in.ibm.com
CC: Pekka Enberg <penberg@cs.helsinki.fi>,
       Peter Zijlstra <peterz@infradead.org>,
       Jim Keniston <jkenisto@us.ibm.com>,
       Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
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       Maneesh Soni <maneesh@in.ibm.com>, Mark Wielaard <mjw@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)
References: <4B5325CF.5000001@redhat.com> <1263740593.557.20967.camel@twins> <4B53661A.9090907@redhat.com> <1263800752.4283.19.camel@laptop> <4B543F93.3060509@redhat.com> <1263815072.4283.305.camel@laptop> <4B544D7C.2060708@redhat.com> <1263816396.4283.361.camel@laptop> <4B544F8E.1080603@redhat.com> <84144f021001180413w76a8ca2axb0b9f07ee4dea67e@mail.gmail.com> <20100118154323.GA4424@in.ibm.com>
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On 01/18/2010 05:43 PM, Ananth N Mavinakayanahalli wrote:
>>
>>> Well, the alternatives are very unappealing.  Emulation and single-stepping
>>> are going to be very slow compared to a couple of jumps.
>>>        
>> So how big chunks of the address space are we talking here for uprobes?
>>      
> As Srikar mentioned, the least we start with is 1 page. Though you can
> have as many probes as you want, there are certain optimizations we can
> do, depending on the most common usecases.
>
> For eg., if you'd consider the start of a routine to be the most
> commonly traced location, most routines in a binary would generally
> start with the same instruction (say push %ebp), and we can refcount a
> slot with that instruction to be used for all probes of the same
> instruction.
>    

But then you can't follow the instruction with a jump back to the code...

-- 
error compiling committee.c: too many arguments to function