lkml.org 
[lkml]   [2006]   [Feb]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Perfctr-devel] Re: [perfmon] perfmon2 code review: 32-bit ABI on 64-bit OS
David Gibson wrote:
> On Sat, Feb 11, 2006 at 02:33:54PM -0800, Stephane Eranian wrote:
[...]
>> The most challenging piece is the IP (program pointer) that is in every
>> sample. Today it is defined as unsigned long because this is fairly
>> natural for a code address. The 64bit OS captures addresses as 64-bit,
>> the 32-bit monitoring tool running on top has to consume them as 64-bit
>> addresses, so u64 would be fine.
>>
>> But not on a 32-bit kernel with a 32-bit tool, addresses exported as u64
>> would certainly work but consume double to buffer space, and that is a
>> more serious issue in my mind.
>
> Hmm.. does the sampling buffer collect on userspace PC values, or
> kernel ones as well?

Either, or both, depending on the measurement settings.

I live in a 64-bit world, so my take on this issue would be to expose
the PC as a uint64_t, always. There is already so much overhead in the
default per-sample header that I wouldn't worry about it.

Now 64 bit might not always be enough. E.g., on PA-RISC. But _I_ do
not care much about Linux on PA.

Eric

--
Eric Gouriou eric.gouriou@hp.com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-02-13 01:08    [W:0.081 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site