RE: [tip:tracing/core] Revert "x86, bts: reenable ptrace branchtrace support"

[Metzger, Markus T]

>-----Original Message-----
>From: tip-bot for Ingo Molnar [mailto:mingo@xxxxxxx]
>Sent: Thursday, June 11, 2009 1:37 AM
>To: linux-tip-commits@xxxxxxxxxxxxxxx
>Cc: hpa@xxxxxxxxx; mingo@xxxxxxxxxx; peterz@xxxxxxxxxxxxx; Metzger, Markus T; oleg@xxxxxxxxxx;
>tglx@xxxxxxxxxxxxx; mingo@xxxxxxx
>Subject: [tip:tracing/core] Revert "x86, bts: reenable ptrace branch trace support"
>
>Commit-ID:  511b01bdf64ad8a38414096eab283c7784aebfc4
>Gitweb:     http://git.kernel.org/tip/511b01bdf64ad8a38414096eab283c7784aebfc4
>Author:     Ingo Molnar <mingo@xxxxxxx>
>AuthorDate: Thu, 11 Jun 2009 00:32:00 +0200
>Committer:  Ingo Molnar <mingo@xxxxxxx>
>CommitDate: Thu, 11 Jun 2009 00:32:00 +0200
>
>Revert "x86, bts: reenable ptrace branch trace support"
>
>This reverts commit 7e0bfad24d85de7cf2202a7b0ce51de11a077b21.
>
>A late objection to the ABI has arrived:
>
>   http://lkml.org/lkml/2009/6/10/253

I thought that this has been resolved. See for example http://lkml.org/lkml/2009/6/10/257.

Peters concerns were that Debug Store details are exposed to user space, which is
not the case. Debug Store itself is fully in-kernel and the expectation of a 
user-defined buffer can be implemented on top of the Debug Store changes that
Peter expects are needed to support PEBS.

A user-defined trace buffer size is required to support different usage models.
Some users only need a small amount of trace, whereas others need a big amount.
The interface will have to reflect that in some way.


regards,
markus.

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