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From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, mbligh@google.com
Subject: Re: [RFC PATCH] LTTng instrumentation mm (updated)
Date: Fri, 30 Nov 2007 14:10:06 -0500	[thread overview]
Message-ID: <20071130191006.GB3955@Krystal> (raw)
In-Reply-To: <1196448122.19681.16.camel@localhost>

* Dave Hansen (haveblue@us.ibm.com) wrote:
> On Fri, 2007-11-30 at 12:05 -0500, Mathieu Desnoyers wrote:
> > 
> > 
> > Given a trace including :
> > - Swapfiles initially used
> > - multiple swapon/swapoff
> > - swap in/out events
> > 
> > We would like to be able to tell which swap file the information has
> > been written to/read from at any given time during the trace.
> 
> Oh, tracing is expected to be on at all times?  I figured someone would
> encounter a problem, then turn it on to dig down a little deeper, then
> turn it off.
> 

Yep, it can be expected to be on at all times, especially on production
systems using "flight recorder" tracing to record information in a
circular buffer, then dumping the buffers when some triggers (error
conditions) happens.

> As for why I care what is in /proc/swaps.  Take a look at this:
> 
> struct swap_info_struct *
> get_swap_info_struct(unsigned type)
> {
>         return &swap_info[type];
> }
> 
> Then, look at the proc functions: 
> 
> static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
> {
>         struct swap_info_struct *ptr;
>         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
> 
>         if (v == SEQ_START_TOKEN)
>                 ptr = swap_info;
> ...
> 
> I guess if that swap_info[] has any holes, we can't relate indexes in
> there right back to /proc/swaps, but maybe we should add some
> information so that we _can_.
> 

The if (!(ptr->flags & SWP_USED) test in swap_next seems to skip the
unused swap_info entries.

Why should we care about get_swap_info_struct always returning a "used"
swap info struct ?

> -- Dave
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

  reply	other threads:[~2007-11-30 19:10 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-13 19:33 [RFC 0/7] LTTng Kernel Instrumentation (Architecture Independent) Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 1/7] Include marker.h in kernel.h -- temporary, for code readability Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 2/7] LTTng instrumentation fs Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 3/7] LTTng instrumentation ipc Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 4/7] LTTng instrumentation kernel Mathieu Desnoyers
2007-11-15 23:30   ` Mike Mason
2007-11-15 23:54     ` Mike Mason
2007-11-16  2:42       ` Mathieu Desnoyers
2007-11-16  2:22     ` Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 5/7] LTTng instrumentation mm Mathieu Desnoyers
2007-11-15 21:06   ` Dave Hansen
2007-11-15 21:51     ` Mathieu Desnoyers
2007-11-15 22:16       ` Dave Hansen
2007-11-16 14:30         ` Mathieu Desnoyers
2007-11-19 18:04           ` Dave Hansen
2007-11-28 14:09             ` [RFC PATCH] LTTng instrumentation mm (using page_to_pfn) Mathieu Desnoyers
2007-11-28 16:54               ` Dave Hansen
2007-11-29  2:34                 ` Mathieu Desnoyers
2007-11-29  6:25                   ` Dave Hansen
2007-11-30 16:11                     ` [RFC PATCH] LTTng instrumentation mm (updated) Mathieu Desnoyers
2007-11-30 17:46                       ` Dave Hansen
2007-11-30 17:05                         ` Mathieu Desnoyers
2007-11-30 18:42                           ` Dave Hansen
2007-11-30 19:10                             ` Mathieu Desnoyers [this message]
2007-12-04 19:15                               ` Frank Ch. Eigler
2007-12-04 19:25                                 ` Mathieu Desnoyers
2007-12-04 19:40                                   ` Dave Hansen
2007-12-04 20:05                                     ` Mathieu Desnoyers
2007-12-04 20:24                                       ` Dave Hansen
2007-12-04 20:28                                       ` Dave Hansen
2007-11-16 14:47         ` [RFC 5/7] LTTng instrumentation mm Mathieu Desnoyers
2007-11-19 18:07           ` Dave Hansen
2007-11-19 18:52             ` Mathieu Desnoyers
2007-11-19 19:00               ` Mathieu Desnoyers
2007-11-19 19:43                 ` Dave Hansen
2007-11-19 19:43               ` Dave Hansen
2007-11-19 19:52                 ` [PATCH] Cast __page_to_pfn to unsigned long in CONFIG_SPARSEMEM Mathieu Desnoyers
2007-11-19 20:09                   ` Dave Hansen
2007-11-19 20:20                     ` [PATCH] Cast page_to_pfn " Mathieu Desnoyers
2007-11-19 21:08                       ` Andrew Morton
2007-11-19 21:19                         ` Dave Hansen
2007-11-19 21:26                           ` Dave Hansen
2007-11-21 20:12                           ` Christoph Lameter
2007-11-20 17:34                         ` Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 6/7] LTTng instrumentation net Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 7/7] Add Markers Into Semaphore Primitives Mathieu Desnoyers

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