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Message-ID: <967027adabdc8aa654cd788b21147427477a0f08.camel@linux.intel.com>
Subject: Re: [PATCH] tracing: Have saved_cmdlines arrays all in one
 allocation
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@vger.kernel.org>, Masami Hiramatsu
 <mhiramat@kernel.org>,  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Mark Rutland <mark.rutland@arm.com>, Vincent Donnefort
 <vdonnefort@google.com>, Sven Schnelle <svens@linux.ibm.com>, Mete Durlu
 <meted@linux.ibm.com>
Date: Tue, 13 Feb 2024 08:35:22 -0800
In-Reply-To: <20240212191336.5c502f78@gandalf.local.home>
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	 <ef94259e139e4579ee27db99975dc4cf397e2a06.camel@linux.intel.com>
	 <20240212191336.5c502f78@gandalf.local.home>
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On Mon, 2024-02-12 at 19:13 -0500, Steven Rostedt wrote:
> On Mon, 12 Feb 2024 15:39:03 -0800
> Tim Chen <tim.c.chen@linux.intel.com> wrote:
>=20
> > > diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_s=
ched_switch.c
> > > index e4fbcc3bede5..210c74dcd016 100644
> > > --- a/kernel/trace/trace_sched_switch.c
> > > +++ b/kernel/trace/trace_sched_switch.c
> > > @@ -201,7 +201,7 @@ static struct saved_cmdlines_buffer *allocate_cmd=
lines_buffer(unsigned int val)
> > >  	int order;
> > > =20
> > >  	/* Figure out how much is needed to hold the given number of cmdlin=
es */
> > > -	orig_size =3D sizeof(*s) + val * TASK_COMM_LEN;
> > > +	orig_size =3D sizeof(*s) + val * (TASK_COMM_LEN + sizeof(int)); =
=20
> >=20
> > Strictly speaking, *map_cmdline_to_pid is unsigned int so it is more co=
nsistent
> > to use sizeof(unsigned) in line above.  But I'm nitpicking and I'm fine=
 to
> > leave it as is.
>=20
> I was thinking about making that into a macro as it is used in two places=
.
>=20
> /* Holds the size of a cmdline and pid element */
> #define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s)		\
> 	(TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
>=20
> 	orig_size =3D sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
>=20
>=20

Looks good. This makes the code more readable.

Tim