---------- Forwarded message ----------
From: stephane eranian <eran...@googlemail.com>
Date: Sat, Dec 13, 2008 at 6:44 PM
Subject: Re: [patch] Performance Counters for Linux, v3
To: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Vince Weaver <vi...@deater.net>, Ingo Molnar <mi...@elte.hu>,
linux-ker...@vger.kernel.org, Thomas Gleixner <t...@linutronix.de>,
Andrew Morton <a...@linux-foundation.org>, Eric Dumazet
<da...@cosmosbay.com>, Robert Richter <robert.rich...@amd.com>, Arjan
van de Veen <ar...@infradead.org>, Peter Anvin <h...@zytor.com>, Paul
Mackerras <pau...@samba.org>, "David S. Miller" <da...@davemloft.net>,
Papi <ptools-perf...@cs.utk.edu>
Peter,
I don't think you understand what libpfm actually does and therefore
you rush to the wrong conclusion.
At its core, libpfm does NOT know anything about the perfmon kernel API.
I think you missed that, unfortunately.
It is a helper library which helps tool writer solves the event-> code
-> counter assignment problems.
That's it. It does not make any perfmon syscall at ALL to do that.
Proof is people have been using it on
Windows, I can also use it on MacOS.
Looking at your proposal, you think you won't need such a library and
that the kernel is
going to do all this for you. Let's go back to your kerneltop program:
KernelTop Options (up to 4 event types can be specified):
-e EID --event_id=EID # event type ID [default: 0]
0: CPU cycles
1: instructions
2: cache accesses
3: cache misses
4: branch instructions
5: branch prediction misses
< 0: raw CPU events
Looks like I can do:
$ kerneltop --event_id=-0x510088
You think users are going to come up with 0x510088 out of the blue?
I want to say:
$ kerneltop --event_id=BR_INST_EXEC --plm=user
Where do you think they are going to get that from?
The kernel or a helper user library?
Do not denigrate other people's software without understanding what it does.
On Sat, Dec 13, 2008 at 12:17 PM, Peter Zijlstra <a.p.zijls...@chello.nl> wrote:
> On Fri, 2008-12-12 at 18:42 +0100, stephane eranian wrote:
>> In fact, I know tools which do not even need a library.
>
> By your own saying, the problem solved by libperfmon is a hard problem
> (and I fully understand that).
>
> Now you say there is software out there that doesn't use libperfmon,
> that means they'll have to duplicate that functionality.
>
> And only commercial software has a clear gain by wastefully duplicating
> that effort. This means there is an active commercial interest to not
> make perfmon the best technical solution there is, which is contrary to
> the very thing Linux is about.
>
> What is worse, you defend that:
>
>> Go ask end-users what they think of that?
>>
>> You don't even need a library. All of this could be integrated into the tool.
>> New processor, just go download the updated version of the tool.
>
> No! what people want is their problem fixed - no matter how. That is one
> of the powers of FOSS, you can fix your problems in any way suitable.
>
> Would it not be much better if those folks duped into using a binary
> only product only had to upgrade their FOSS kernel, instead of possibly
> forking over more $$$ for an upgrade?
>
> You have just irrevocably proven to me this needs to go into the kernel,
> as the design of perfmon is little more than a GPL circumvention device
> - independent of whether you are aware of that or not.
>
> For that I hereby fully NAK perfmon
>
> Nacked-by: Peter Zijlstra <a.p.zijls...@chello.nl>
>
>
>
>
------------------------------------------------------------------------------
SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada.
The future of the web can't happen without you. Join us at MIX09 to help
pave the way to the Next Web now. Learn more and register at
http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/
_______________________________________________
perfmon2-devel mailing list
perfmon2-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
