From: Vaibhav Nagarnaik <vnagarnaik@google.com>
To: David Sharp <dhsharp@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Michael Rubin <mrubin@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 4/5] trace: Make removal of ring buffer pages atomic
Date: Tue, 23 Aug 2011 12:20:14 -0700 [thread overview]
Message-ID: <CAL26m8J29HA89m-r0EXRxn_hRoBkDksXXfgO4A12256i+0aamg@mail.gmail.com> (raw)
In-Reply-To: <CAJL_ektp-BP52Qqfu_bBDjUnXyX20PWzgNuQF_atB0J9q7n=Zw@mail.gmail.com>
On Tue, Aug 23, 2011 at 12:16 PM, David Sharp <dhsharp@google.com> wrote:
> On Tue, Aug 23, 2011 at 11:55 AM, Vaibhav Nagarnaik
> <vnagarnaik@google.com> wrote:
>> This patch adds the capability to remove pages from a ring buffer
>> without destroying any existing data in it.
>>
>> This is done by removing the pages after the tail page. This makes sure
>> that first all the empty pages in the ring buffer are removed. If the
>> head page is one in the list of pages to be removed, then the page after
>> the removed ones is made the head page. This removes the oldest data
>> from the ring buffer and keeps the latest data around to be read.
>>
>> To do this in a non-racey manner, tracing is stopped for a very short
>> time while the pages to be removed are identified and unlinked from the
>> ring buffer. The pages are freed after the tracing is restarted to
>> minimize the time needed to stop tracing.
>>
>> The context in which the pages from the per-cpu ring buffer are removed
>> runs on the respective CPU. This minimizes the events not traced to only
>> NMI trace contexts.
>
> "interrupt contexts". We're not disabling interrupts.
>
Since the reader_lock is held using spin_lock_irq(), there won't be IRQs
coming in, only the NMIs.
Vaibhav Nagarnaik
next prev parent reply other threads:[~2011-08-23 19:20 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-26 22:59 [PATCH 0/5] Add dynamic updates to trace ring buffer Vaibhav Nagarnaik
2011-07-26 22:59 ` [PATCH 1/5] trace: Add a new readonly entry to report total buffer size Vaibhav Nagarnaik
2011-07-29 18:01 ` Steven Rostedt
2011-07-29 19:09 ` Vaibhav Nagarnaik
2011-07-26 22:59 ` [PATCH 2/5] trace: Add ring buffer stats to measure rate of events Vaibhav Nagarnaik
2011-07-29 18:10 ` Steven Rostedt
2011-07-29 19:10 ` Vaibhav Nagarnaik
2011-07-26 22:59 ` [PATCH 3/5] trace: Add per_cpu ring buffer control files Vaibhav Nagarnaik
2011-07-29 18:14 ` Steven Rostedt
2011-07-29 19:13 ` Vaibhav Nagarnaik
2011-07-29 21:25 ` Steven Rostedt
2011-07-26 22:59 ` [PATCH 4/5] trace: Make removal of ring buffer pages atomic Vaibhav Nagarnaik
2011-07-29 21:23 ` Steven Rostedt
2011-07-29 23:30 ` Vaibhav Nagarnaik
2011-07-30 1:12 ` Steven Rostedt
2011-07-30 1:50 ` David Sharp
2011-07-30 2:43 ` Steven Rostedt
2011-07-30 3:44 ` David Sharp
2011-07-26 22:59 ` [PATCH 5/5] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 0/5] Add dynamic updates to trace ring buffer Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 1/5] trace: Add a new readonly entry to report total buffer size Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 2/5] trace: Add ring buffer stats to measure rate of events Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 3/5] trace: Add per_cpu ring buffer control files Vaibhav Nagarnaik
2011-08-22 20:29 ` Steven Rostedt
2011-08-22 20:36 ` Vaibhav Nagarnaik
2011-08-22 22:09 ` [PATCH v3] " Vaibhav Nagarnaik
2011-08-23 0:49 ` Steven Rostedt
2011-08-23 1:16 ` Vaibhav Nagarnaik
2011-08-23 1:17 ` Vaibhav Nagarnaik
2011-09-03 2:45 ` Steven Rostedt
2011-09-06 18:56 ` Vaibhav Nagarnaik
2011-09-07 17:13 ` Steven Rostedt
2011-10-12 1:20 ` [PATCH v4 1/4] " Vaibhav Nagarnaik
2012-01-31 23:53 ` Vaibhav Nagarnaik
2012-02-02 2:42 ` Steven Rostedt
2012-02-02 19:20 ` Vaibhav Nagarnaik
2012-02-02 20:00 ` [PATCH v5 " Vaibhav Nagarnaik
2012-02-02 20:00 ` [PATCH v5 2/4] trace: Make removal of ring buffer pages atomic Vaibhav Nagarnaik
2012-04-21 4:27 ` Steven Rostedt
2012-04-23 17:31 ` Vaibhav Nagarnaik
2012-04-25 21:18 ` [PATCH v6 1/3] " Vaibhav Nagarnaik
2012-04-25 21:18 ` [PATCH v6 2/3] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2012-04-25 21:18 ` [PATCH v6 3/3] trace: change CPU ring buffer state from tracing_cpumask Vaibhav Nagarnaik
2012-05-03 1:55 ` [PATCH v6 1/3] trace: Make removal of ring buffer pages atomic Steven Rostedt
2012-05-03 6:40 ` Vaibhav Nagarnaik
2012-05-03 12:57 ` Steven Rostedt
2012-05-03 14:12 ` Steven Rostedt
2012-05-03 18:43 ` Vaibhav Nagarnaik
2012-05-03 18:54 ` Steven Rostedt
2012-05-03 18:54 ` Vaibhav Nagarnaik
2012-05-04 1:59 ` [PATCH v7 " Vaibhav Nagarnaik
2012-05-04 1:59 ` [PATCH v7 2/3] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2012-05-19 10:18 ` [tip:perf/core] ring-buffer: " tip-bot for Vaibhav Nagarnaik
2012-05-04 1:59 ` [PATCH v7 3/3] trace: change CPU ring buffer state from tracing_cpumask Vaibhav Nagarnaik
2012-05-19 10:21 ` [tip:perf/core] tracing: " tip-bot for Vaibhav Nagarnaik
2012-05-07 20:22 ` [PATCH v7 1/3] trace: Make removal of ring buffer pages atomic Steven Rostedt
2012-05-07 21:48 ` Vaibhav Nagarnaik
2012-05-08 0:14 ` Steven Rostedt
2012-05-09 3:38 ` Steven Rostedt
2012-05-09 5:00 ` Vaibhav Nagarnaik
2012-05-09 14:29 ` Steven Rostedt
2012-05-09 17:46 ` Vaibhav Nagarnaik
2012-05-09 17:54 ` Steven Rostedt
2012-05-19 10:17 ` [tip:perf/core] ring-buffer: " tip-bot for Vaibhav Nagarnaik
2012-02-02 20:00 ` [PATCH v5 3/4] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2012-02-02 20:00 ` [PATCH v5 4/4] trace: change CPU ring buffer state from tracing_cpumask Vaibhav Nagarnaik
2012-03-08 23:51 ` [PATCH v5 1/4] trace: Add per_cpu ring buffer control files Vaibhav Nagarnaik
2012-05-02 21:03 ` [tip:perf/core] ring-buffer: " tip-bot for Vaibhav Nagarnaik
2011-10-12 1:20 ` [PATCH v4 2/4] trace: Make removal of ring buffer pages atomic Vaibhav Nagarnaik
2011-10-12 1:20 ` [PATCH v4 3/4] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2011-10-12 1:20 ` [PATCH v4 4/4] trace: change CPU ring buffer state from tracing_cpumask Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 4/5] trace: Make removal of ring buffer pages atomic Vaibhav Nagarnaik
2011-08-23 3:27 ` Steven Rostedt
2011-08-23 18:55 ` Vaibhav Nagarnaik
2011-08-23 18:55 ` [PATCH v3 " Vaibhav Nagarnaik
2011-08-23 19:16 ` David Sharp
2011-08-23 19:20 ` Vaibhav Nagarnaik [this message]
2011-08-23 19:24 ` Steven Rostedt
2011-08-23 18:55 ` [PATCH v3 5/5] trace: Make addition of pages in ring buffer atomic Vaibhav Nagarnaik
2011-08-16 21:46 ` [PATCH v2 " Vaibhav Nagarnaik
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