Date: Wed, 2 Aug 2006 23:52:19 -0700
From: Andrew Morton <akpm@osdl.org>
To: Jay Lan <jlan@engr.sgi.com>
Cc: linux-kernel@vger.kernel.org, nagar@watson.ibm.com, balbir@in.ibm.com,
       jes@sgi.com, csturtiv@sgi.com, tee@sgi.com,
       guillaume.thouvenin@bull.net
Subject: Re: [patch 1/3] basic accounting over taskstats
Message-Id: <20060802235219.25a072e7.akpm@osdl.org>
In-Reply-To: <44D179A5.4000606@engr.sgi.com>
References: <44D179A5.4000606@engr.sgi.com>
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On Wed, 02 Aug 2006 21:20:53 -0700
Jay Lan <jlan@engr.sgi.com> wrote:

> This patch is to replace the "[patch 1/3] add basic accounting
> fields to taskstats" posted on 7/31.
> 
> This patch adds some basic accounting fields to the taskstats
> struct, add a new kernel/tsacct.c to handle basic accounting
> data handling upon exit. A handle is added to taskstats.c
> to invoke the basic accounting data handling.
> 

> +#define TS_COMM_LEN		16	/* should sync up with TASK_COMM_LEN
> +					 * in linux/sched.h */

There was a proposal recently to increase TASK_COMM_LENGTH from 16 to 20 so
that it was long enough to hold an entire IEEE(?) UUID so that the
operator can easily match up a kernel thread with the storage device which
it manages.

I don't know if/when that change will happen, but the message is that
TASK_COMM_LENGTH may increase.

> +	BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN);

And if it does, we'll need to increase TS_COMM_LEN as well.  That will
amount to an non-compatible change to the interface which you are
proposing.   We want to avoid that.

Hence I'd propose that you increase TS_COMM_LEN to 32 or something and if
TASK_COMM_LEN later becomes really big, we might just choose to truncate
it.

Or we remove this field altogether, perhaps.  The same info is available
from /proc/pid/stat anyway.  Is it really needed?

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