From: Andrew Morton <akpm@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Pierre Ossman <drzeus@drzeus.cx>, Pekka Paalanen <pq@iki.fi>,
Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH 4/4] ring-buffer: only allocate buffers for online cpus
Date: Wed, 11 Mar 2009 20:32:22 -0700 [thread overview]
Message-ID: <20090311203222.7515107d.akpm@linux-foundation.org> (raw)
In-Reply-To: <20090312023936.696105567@goodmis.org>
On Wed, 11 Mar 2009 22:37:24 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> From: Steven Rostedt <srostedt@redhat.com>
>
> Impact: save on memory
>
> Currently, a ring buffer was allocated for each "possible_cpus". On
> some systems, this is the same as NR_CPUS. Thus, if a system defined
> NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless
> ring buffers taking up space. With a default buffer of 3 megs, this
> could be quite drastic.
>
> This patch changes the ring buffer code to only allocate ring buffers
> for online CPUs. If a CPU goes off line, we do not free the buffer.
> This is because the user may still have trace data in that buffer
> that they would like to look at.
>
> Perhaps in the future we could add code to delete a ring buffer if
> the CPU is offline and the ring buffer becomes empty.
>
> ...
>
> +#ifdef CONFIG_HOTPLUG
> +#ifdef CONFIG_HOTPLUG
> +#ifdef CONFIG_HOTPLUG
> +#ifdef CONFIG_HOTPLUG
> +#ifdef CONFIG_HOTPLUG
CONFIG_HOTPLUG_CPU
next prev parent reply other threads:[~2009-03-12 3:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-12 2:37 [PATCH 0/4] [GIT PULL] memory saving ring buffer for tip/tracing/ftrace Steven Rostedt
2009-03-12 2:37 ` [PATCH 1/4] tracing: keep ring buffer to minimum size till used Steven Rostedt
2009-03-12 3:26 ` Andrew Morton
2009-03-12 13:25 ` Steven Rostedt
2009-03-12 15:01 ` Frederic Weisbecker
2009-03-12 15:14 ` Steven Rostedt
2009-03-12 2:37 ` [PATCH 2/4] tracing: expand the ring buffers when an event is activated Steven Rostedt
2009-03-12 2:37 ` [PATCH 3/4] tracing: fix trace_wait to know to wait on all cpus or just one Steven Rostedt
2009-03-12 2:37 ` [PATCH 4/4] ring-buffer: only allocate buffers for online cpus Steven Rostedt
2009-03-12 3:32 ` Andrew Morton [this message]
2009-03-12 13:29 ` Steven Rostedt
2009-03-12 7:31 ` KOSAKI Motohiro
2009-03-12 13:38 ` Steven Rostedt
2009-03-12 23:47 ` KOSAKI Motohiro
2009-03-12 7:07 ` [PATCH 0/4] [GIT PULL] memory saving ring buffer for tip/tracing/ftrace Pierre Ossman
2009-03-12 7:34 ` KOSAKI Motohiro
2009-03-12 9:20 ` Pierre Ossman
2009-03-12 13:39 ` Steven Rostedt
2009-03-12 10:47 ` Neil Horman
2009-03-12 12:12 ` Pierre Ossman
2009-03-12 13:12 ` Neil Horman
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