Add explanation of the profile feedback build to the README

Also explains that the are additional warnings.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/INSTALL b/INSTALL
index 16e45f114f18d5d6964ab9fa39eee617dfa59bfc..bbb9d4dc9ab37a242d8accb86fa8a0d35d677ab8 100644 (file)
--- a/INSTALL
+++ b/INSTALL
@@ -25,6 +25,19 @@ set up install paths (via config.mak.autogen), so you can write instead
        $ make all doc ;# as yourself
        # make install install-doc install-html;# as root
 
+If you're willing to trade off (much) longer build time for a later
+faster git you can also do a profile feedback build with
+
+       $ make profile-all
+       # make prefix=... install
+
+This will run the complete test suite as training workload and then
+rebuild git with the generated profile feedback. This results in a git
+which is a few percent faster on CPU intensive workloads.  This
+may be a good tradeoff for distribution packagers.
+
+Note that the profile feedback build stage currently generates
+a lot of additional compiler warnings.
 
 Issues of note: