linux-kernel - Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount

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Message-ID: <CA+icZUWHS2QeWTN0a8DwmMJ1UnvKjvox8t9MTLXMMU8oQOHtCQ@mail.gmail.com>
Date:	Mon, 2 Sep 2013 12:30:45 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Waiman Long <waiman.long@...com>, Ingo Molnar <mingo@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...hat.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless
 update of refcount

On Sun, Sep 1, 2013 at 5:55 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Sun, Sep 1, 2013 at 8:45 AM, Sedat Dilek <sedat.dilek@...il.com> wrote:
>>
>> Samples: 160K of event 'cycles:pp', Event count (approx.): 77003901089
>> +  12,46%  t_lockref_from-  [kernel.kallsyms]     [k] irq_return
>> +   4,86%  t_lockref_from-  [kernel.kallsyms]     [k] lockref_get_or_lock
>> +   4,42%  t_lockref_from-  [kernel.kallsyms]     [k] __ticket_spin_lock
>> +   4,28%  t_lockref_from-  [kernel.kallsyms]     [k] __acct_update_integrals
>
> You need to go into __ticket_spin_lock to see who the callers are.
>
> Just go down to it and press enter to expand it (and then you need to
> go and expand that entry too to get the callers)
>

I am new to perf usage.

  4,60%  t_lockref_from-  [kernel.kallsyms]     [k] __ticket_spin_lock

Which entry to select?

Annotate __ticket_spin_lock
Zoom into t_lockref_from-(3962) thread
Zoom into the Kernel DSO
Browse map details
Run scripts for samples of thread [t_lockref_from-]
Run scripts for samples of symbol [__ticket_spin_lock]
Run scripts for all samples
Switch to another data file in PWD
Exit

> I still don't know how you get to irq_return. It should use sysret. Odd.

- Sedat -
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