https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97834
Bug ID: 97834
Summary: gcov-instrumented binaries are very slow due to
unbuffered IO
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: gcov-profile
Assignee: unassigned at gcc dot gnu.org
Reporter: roland.illig at gmx dot de
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Since 2003-05-14, gcov_open calls setbuf (gcov_var.file, (char *)0), thereby
slowing down the instrumentation a lot.
https://github.com/gcc-mirror/gcc/commit/7d63a2fae019a83772ebae65689f4113a0eb4bec
For example, running the 343 unit tests in NetBSD/src/usr.bin/make takes about
14 minutes when running in unbuffered mode, and 30 seconds in buffered mode.
The commit itself does not mention why the unbuffered IO is needed.
I manually patched the instrumented binary by commenting out the call to
setbuf, and the results are still the same.
Please consider removing that call to setbuf.
