I don't know whether it is beneficial or not - but having the capability to build LTO without PGO seems reasonable. I can review any pull requests altering configure.ac and Makefile.pre.in to make such a change.
-@gpshead On Mon, Aug 7, 2017 at 5:08 PM Soldea, Octavian <octavian.sol...@intel.com> wrote: > Hello > > Thank you for your messages. I am not quite sure I understood, therefore, > I would like to ask if you see beneficial to have the option of lto > separately? > > Best regards, > Octavian > > > > > > > -----Original Message----- > From: Wang, Peter Xihong > Sent: Monday, August 7, 2017 5:00 PM > To: Victor Stinner <victor.stin...@gmail.com>; Soldea, Octavian < > octavian.sol...@intel.com> > Cc: Python-Dev@python.org > Subject: RE: [Python-Dev] first post introduction and question regarding > lto > > We evaluated different tests before setting down and proposing regrtest > suite for PGO training, including using OpenStack benchmarks for OpenStack > applications. The regrtest suite was found consistently giving the best in > terms of performance across applications/workloads. > > So I would hesitate to remove any test from the training suite (for the > purpose of reducing build time), unless we are absolute sure it will not > hurt performance across the board. > > Thanks, > > Peter > > -----Original Message----- > From: Python-Dev [mailto:python-dev-bounces+peter.xihong.wang= > intel....@python.org] On Behalf Of Victor Stinner > Sent: Monday, August 07, 2017 4:43 PM > To: Soldea, Octavian <octavian.sol...@intel.com> > Cc: Python-Dev@python.org > Subject: Re: [Python-Dev] first post introduction and question regarding > lto > > I don't think that PGO compilation itself is slow. Basically, I expect > that it only doubles the compilation time, but compiling Python takes less > than 1 minute usually. The slow part is the profiling task: run the full > Python test suite, which takes at least 20 minutes. The tests must be run > sequentially. > > It would help to reduce the number of tests run in the profiling task. > We should also maybe skip tests which depend too much on I/O to get more > reproductible PGO performances. > > Victor > > 2017-08-08 1:01 GMT+02:00 Soldea, Octavian <octavian.sol...@intel.com>: > > Hello > > > > > > > > Gregory: Thank you for your message. I really appreciate it. > > > > > > > > In my opinion the use of lto only compilation mode can be of benefit > > from two reasons at least: > > > > 1. Lto only can provide a platform for experimentations. Of > course, it > > seems to be very application specific. > > > > 2. Lto compilation is faster than an entire pgo + lto mode. While > pgo > > can take a lot of time, lto can provide significant optimizations, as > > compared to baseline, at the cost of less compilation time. Of course, > > lto is time consuming. To the best of my knowledge, compiling with lto > > only is shorter than combining pgo and lto. > > > > > > > > In this context, I will be more than happy to receive more feedback > > and opinions. > > > > > > > > Best regards, > > > > Octavian > > > > > > > > > > > > > > > > > > > > From: Gregory P. Smith [mailto:g...@krypto.org] > > Sent: Monday, August 7, 2017 3:12 PM > > To: Soldea, Octavian <octavian.sol...@intel.com>; > > Python-Dev@python.org > > Subject: Re: [Python-Dev] first post introduction and question > > regarding lto > > > > > > > > I've personally never seen a situation where PGO is not desired yet > > some other fancier optimization such as LTO is. When do you encounter > > people wanting that? PGO always produces a 10-20% faster CPython > interpreter. > > > > > > > > I have no problem with patches enabling an LTO only build for anyone > > who wants one if they do not already exist. At the moment I'm not > > sure which LTO toolchains actually work properly. We removed it from > > inclusion in --enable-optimizations because it was clearly broken in > > some common environments. > > > > > > > > If LTO without PGO is useful, making it work is probably just a matter > > of making sure @LTOFLAGS@ show up on the non-PGO related > > Makefile.pre.in targets as well as updating the help text for > --with-lto in configure.ac. > > [untested] > > > > > > > > -gps > > > > > > > > > > Python-Dev mailing list > > Python-Dev@python.org > > https://mail.python.org/mailman/listinfo/python-dev > > Unsubscribe: > > https://mail.python.org/mailman/options/python-dev/greg%40krypto.org > > > > > > _______________________________________________ > > Python-Dev mailing list > > Python-Dev@python.org > > https://mail.python.org/mailman/listinfo/python-dev > > Unsubscribe: > > https://mail.python.org/mailman/options/python-dev/victor.stinner%40gm > > ail.com > > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/peter.xihong.wang%40intel.com > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/greg%40krypto.org >
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