Messages in this thread | | | Date | Sun, 12 Feb 2006 16:03:44 -0800 | From | Eric Gouriou <> | Subject | Re: [Perfctr-devel] Re: [perfmon] perfmon2 code review: 32-bit ABI on 64-bit OS |
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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/
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