linux-kernel - Re: [PATCH] x86: add the debugfs interface for the sysprof tool

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Date:	Sat, 23 Feb 2008 16:54:49 +0200
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"Arjan van de Ven" <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, sandmann@...hat.com,
	tglx@...x.de, hpa@...or.com
Subject: Re: [PATCH] x86: add the debugfs interface for the sysprof tool

On Sat, Feb 23, 2008 at 10:11 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>  Seems a poor idea to me.  Sure, oprofile is "hard to set up", but not if
>  your distributor already did it for you.
>
>  Sidebar: the code uses the utterly crappy register_timer_hook() which
>
>  a) is woefully misnamed and
>
>  b) is racy and
>
>  c) will disrupt oprofile if it is being used.  And vice versa.

I wonder if sysprof should hook to the same interrupt as oprofile then?

On Sat, Feb 23, 2008 at 10:11 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>  This code adds a new kernel->userspace interface which is not even
>  documented in code comments.  It appears to use a pollable debugfs file in
>  /proc somewhere, carrying an unspecified payload.

[snip]

>  This reads a single item even if there were 100 queued, which is quite
>  inefficient.
>
>  We already have infrastructure for bulk kernel->user transfer in
>  kernel/relay.c?

Agreed. This seems like a perfect fit with relayfs.
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