linux-kernel - Re: HW breakpoints perf

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Date:	Wed, 13 Jan 2010 18:21:20 -0800
From:	Joshua Pincus <joshua.pincus@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>, peterz@...radead.org,
	paulus@...ba.org, acme@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: HW breakpoints perf_events request

Hi,

On Wed, Jan 13, 2010 at 6:15 PM, Andi Kleen <andi@...stfloor.org> wrote:
> Joshua Pincus <joshua.pincus@...il.com> writes:
>
>> I have a request for an additional feature to be included
>> in the recent hardware breakpoints work soon to be delivered
>> in kernel 2.6.33.
>
> Sounds to me like the existing ptrace based interface
> can practically all you want
>
> (except that the "parent signal" would be wait and for
> fork/exec you have to explicitely attach)

We would like to avoid using ptrace at all costs.
It requires us to have a parent thread running
which monitors all the others.  It's not clear that
the wait() call by the parent doesn't mask a barrage
of signals from various threads and the performance
penalty is huge in multi-threaded apps.

If we could get this functionality working w/o ptrace,
we'd be very, very happy and grateful.

>
> -Andi
>

Thanks,
JP
--
On Wed, Jan 13, 2010 at 6:15 PM, Andi Kleen <andi@...stfloor.org> wrote:
> Joshua Pincus <joshua.pincus@...il.com> writes:
>
>> I have a request for an additional feature to be included
>> in the recent hardware breakpoints work soon to be delivered
>> in kernel 2.6.33.
>
> Sounds to me like the existing ptrace based interface
> can practically all you want
>
> (except that the "parent signal" would be wait and for
> fork/exec you have to explicitely attach)
>
> -Andi
>
> --
> ak@...ux.intel.com -- Speaking for myself only.
>
--
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