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Diffstat (limited to 'mdk-stage1/dietlibc/profiling/README')
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diff --git a/mdk-stage1/dietlibc/profiling/README b/mdk-stage1/dietlibc/profiling/README new file mode 100644 index 000000000..0a0293073 --- /dev/null +++ b/mdk-stage1/dietlibc/profiling/README @@ -0,0 +1,37 @@ + + Notes on profiling support for dietlibc + + 1.) A big problem when doing profiling on statically linked + programs, is that the internal profiling functions (mcount + and friends) will be included in the call graph although + they would not if the program would have been dynamically + linked. This is because every symbol between .text and + _etext is included in the call-graph. If a program is + dynamically linked, then mcount and friends are not between + .text and _etext, so they are not included. A workaround + for this, would be to put mcount, __mcount, monitor and + profiler into another section (eg. ".profile"), but this + creates some strange problems, I'm currently not aware of. + If you want to debug this: Putting a function into a specific + section works like this (with gcc): + + void foo (int bar) __attribute__ ((section(".foobar"))) + + 2.) _start may randomly be found in the callgraph. I don't + know why. May be a bug in gprof. + + 3.) The profiling is a complete rewrite, though I looked at + the glibc Version for inspiration. Please note that this + version might not be as portable as the glibc version but + its much smaller (although this is not a really important + argument, as profiled binaries seldom get shipped) and + hopefully easier to understand. + + 4.) all objects that should be profiled mustn't be compiled + with -fomit-frame-pointer (as with glibc). Add + -fno-fomit-frame-pointer to $CFLAGS if you're encountering + weird problems. + + 5.) There is currently no basic-block statistic support. + +Please send comments and bug reports to: tom@rhadamanthys.org |