From: Mikulas Patocka <mpatocka@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Mike Snitzer <msnitzer@redhat.com>,
Laurence Oberman <loberman@redhat.com>,
Tao Ma <boyu.mt@taobao.com>, Robin Dong <sanbai@alibaba-inc.com>,
dm-devel@redhat.com, Coly Li <colyli@gmail.com>,
"Alasdair G. Kergon" <agk@redhat.com>
Subject: Re: [PATCH 2/4] dm stats: support precise timestamps
Date: Wed, 17 Jun 2015 09:17:40 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1506170908070.15768@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20150617014324.GA30214@redhat.com>
On Tue, 16 Jun 2015, Vivek Goyal wrote:
> On Tue, Jun 16, 2015 at 03:27:48PM -0400, Mikulas Patocka wrote:
> >
> >
> > On Tue, 16 Jun 2015, Vivek Goyal wrote:
> >
> > > On Tue, Jun 09, 2015 at 05:21:39PM -0400, Mikulas Patocka wrote:
> > >
> > > [..]
> > > > Messages
> > > > ========
> > > >
> > > > - @stats_create <range> <step> [<program_id> [<aux_data>]]
> > > > + @stats_create <range> <step>
> > > > + [<number_of_optional_arguments> <optional_arguments>...]
> > > > + [<program_id> [<aux_data>]]
> > > >
> > > > Create a new region and return the region_id.
> > > >
> > > > @@ -48,6 +54,17 @@ Messages
> > > > "/<number_of_areas>" - the range is subdivided into the specified
> > > > number of areas.
> > > >
> > > > + <number_of_optional_arguments>
> > > > + The number of optional arguments
> > > > +
> > > > + <optional_arguments>
> > > > + The following optional arguments are supported
> > > > + precise_timestamps - use precise timer with nanosecond resolution
> > > > + instead of the "jiffies" variable. When this argument is
> > > > + used, the resulting times are in nanoseconds instead of
> > > > + milliseconds. Precise timestamps are a little bit slower
> > > > + to obtain than jiffies-based timestamps.
> > > > +
> > >
> > > Instead of "precise_timestams" will it make sense to call it
> > > "nanosecond_timestamps" or "ns_timestamps".
> > >
> > >
> > > > <program_id>
> > > > An optional parameter. A name that uniquely identifies
> > > > the userspace owner of the range. This groups ranges together
> > >
> > > We are adding these new parameters/arguments in between existing parameters.
> > > Will it break any of the existing scritps. Will it make sense to add these
> > > new parameters at the end. It is more intuitive.
> >
> > It could break someone who uses number as program_id - but there is no
> > program on Linux with name that is a pure number.
> >
>
> There does not seem to be any restriction that program_id has to be
> a valid program name. It could be any string. I used a program id
> of 25 and it works.
The purpose of program_id is that different programs don't step over each
other's statistics. Your program should use the program name as program_id
to make sure that it doesn't collide.
> [root@tiger ~]# dmsetup message docker-docker--pool 0 @stats_create - /1
> 25
> 0
>
> [root@tiger ~]# dmsetup message docker-docker--pool 0 @stats_create - /2
> 30
> 1
>
> [root@tiger ~]# dmsetup message docker-docker--pool 0 @stats_list 25
> 0: 0+585465856 585465856 25 -
>
> [root@tiger ~]# dmsetup message docker-docker--pool 0 @stats_list
> 0: 0+585465856 585465856 25 -
> 1: 0+585465856 292732928 30 -
>
> May be we can introduce a new message to handle this new number of
> arguments syntax. Say "stats_create_v2". That way existing programs
> will not be broken, if any.
There are no existing programs that use numbers as program_id.
> > We can't add it at the end because program_id and aux_data are already
> > optional arguments.
> >
> > > Also, I was wondering that why do we need to introduce this notion of
> > > number of optional arguments. Can't we just introduce another optional
> > > parameter [ns_timestamps]. That feels little simpler.
> >
> > Then, it will clash with program_id "ns_timestamps". Device mapper uses
> > this "number of optional arguments" notation at other places, so I used it
> > too,
>
> BTW, I have a very stupid question. This probably stems from the fact that
> I don't know enough about dm argument parsing.
>
> Why can't I pass the argument in same format as command line. So how
> about.
>
> @stats_create [program_id=<program_id>] [aux_data=<aux_data>]
>
> That way we know what arguments are coming. There is no guessing and
> handling optional parameters is easy too.
Other dm targets don't use this style of argument passing.
Mikulas
> Thanks
> Vivek
>
next prev parent reply other threads:[~2015-06-17 13:17 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 21:20 [PATCH 0/4] Integrate dm-latency functionality to dm-statistics Mikulas Patocka
2015-06-09 21:21 ` [PATCH 1/4] dm-statistics: better argument validation Mikulas Patocka
2015-06-09 21:21 ` [PATCH 2/4] dm stats: support precise timestamps Mikulas Patocka
2015-06-10 17:10 ` Mike Snitzer
2015-06-10 17:33 ` Mikulas Patocka
2015-06-10 17:40 ` Mike Snitzer
2015-06-13 17:03 ` Coly Li
2015-06-15 13:04 ` Mikulas Patocka
2015-06-15 14:17 ` Coly Li
2015-06-16 15:33 ` Vivek Goyal
2015-06-16 19:27 ` Mikulas Patocka
2015-06-17 1:43 ` Vivek Goyal
2015-06-17 13:17 ` Mikulas Patocka [this message]
2015-06-17 13:20 ` Vivek Goyal
2015-06-17 15:18 ` Bryn M. Reeves
2015-06-17 14:54 ` Bryn M. Reeves
2015-06-17 14:52 ` Bryn M. Reeves
2015-07-27 15:11 ` Bryn M. Reeves
2015-06-09 21:22 ` [PATCH 3/4] dm stats: report histogram of latencies Mikulas Patocka
2015-06-13 17:03 ` Coly Li
2015-06-15 13:06 ` Mikulas Patocka
2015-06-15 14:41 ` Coly Li
2015-06-15 15:34 ` Mikulas Patocka
2015-06-16 16:21 ` Vivek Goyal
2015-06-09 21:22 ` [PATCH 4/4] dm stats: support statistics on requests-based devices Mikulas Patocka
2015-06-09 21:23 ` Laurence Oberman
2015-06-13 17:02 ` [PATCH 0/4] Integrate dm-latency functionality to dm-statistics Coly Li
2015-06-15 12:47 ` Mikulas Patocka
2015-06-15 14:35 ` Coly Li
2015-06-17 13:22 ` Mikulas Patocka
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