I'm curious about what workloads / benchmarks you considered for this activity - the traditional spec benchmarks don't really trigger anything in libatomic - so where do we see the improvements or none ?
regards Ramana
________________________________________ From: linaro-toolchain linaro-toolchain-bounces@lists.linaro.org on behalf of Yvan Roux yvan.roux@linaro.org Sent: 27 June 2016 20:04:52 To: Pinski, Andrew Cc: Linaro Toolchain Mailman List Subject: Re: [ACTIVITY] Week 25
Hi Andrew,
On 27 June 2016 at 19:32, Pinski, Andrew Andrew.Pinski@cavium.com wrote:
No gain expected in implementing an Ifunc'ed version of the library.How did you prove that? What hardware did you run this on to prove it? Also have you thought at least doing an ifunc version for 128bit atomics?
up to 64bits, the calls to the libatomic routines are inlined and armv8.1 CAS and load-operate version are used when the application is build for armv8.1 architecture. For 128bits, a call to the lib is made which uses the same LL/SC implementation with or without LSE support, as CAS and load-operate instruction don't support this data size.
I don't have armv8.1 hardware and made the analysis on the generated assembler. Do you have use case on your side where an ifunc version can be useful ? I'm not aware of an algorithm which can replace effectively LL/SC implementation with shorter CAS, do you have any pointers ? Maybe CASP can be used in some cases, I'll investigate it.
Thanks Yvan
Thanks, Andrew
-----Original Message----- From: linaro-toolchain [mailto:linaro-toolchain-bounces@lists.linaro.org] On Behalf Of Yvan Roux Sent: Monday, June 27, 2016 1:40 AM To: Linaro Toolchain Mailman List linaro-toolchain@lists.linaro.org Subject: [ACTIVITY] Week 25
== Progress == o Extended Validation (1/10)
- Benchmarking job babysitting.
o Upstream GCC (4/10) - ARMv8.1 libatomic: Analysis completed. No gain expected in implementing an Ifunc'ed version of the library. - Working on __sync buitlins potential fix.
o Misc (5/10)
- Various meetings and discussions.
- Internal appraisal
== Plan == o Continue on-going tasks (__sync, benchmarking) _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org https://lists.linaro.org/mailman/listinfo/linaro-toolchain
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