From mboxrd@z Thu Jan 1 00:00:00 1970 From: der.herr@hofr.at (Nicholas Mc Guire) Date: Wed, 18 Feb 2015 20:02:14 +0100 Subject: unlikely compiler flag propagation In-Reply-To: <24781.1424285845@turing-police.cc.vt.edu> References: <20150218182453.GB21740@kroah.com> <20150218183801.GA1773@opentech.at> <24781.1424285845@turing-police.cc.vt.edu> Message-ID: <20150218190214.GA17616@opentech.at> To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org On Wed, 18 Feb 2015, Valdis.Kletnieks at vt.edu wrote: > On Wed, 18 Feb 2015 19:38:01 +0100, Nicholas Mc Guire said: > > On Wed, 18 Feb 2015, Greg KH wrote: > > > interesting - would you have a reference to some talk/paper/data/... ? > > Test for yourself :) > > config PROFILE_ANNOTATED_BRANCHES > bool "Trace likely/unlikely profiler" > select TRACE_BRANCH_PROFILING > help > This tracer profiles all likely and unlikely macros > in the kernel. It will display the results in: > > /sys/kernel/debug/tracing/trace_stat/branch_annotated > > Note: this will add a significant overhead; only turn this > on if you need to profile the system's use of these macros. > was not aware of that - many thanks ! I do assume that such a claim of 90% not being effective would not be based on testing some single system but based on a much wider basis so that data would be interesting to see data from different clases of systems. thx! hofrat