I have been investigating some build performance issues, and trying to narrow down causes of slowness, and observed an odd effect, which was suggested by a huge time difference between building from git and building from a tarball.

If I do

    make -C src/port all

and then wait 10 seconds or so and do

    make -j 3

or even just plain

    make

the build finishes much much faster (like 1m vs 5m) than if I had not run the first command.

I have seen this on a Fedora VM (VirtualBox, W7 host, Athlon II X2) and a ScientificLinux 6 machine (dual quad xeon E5620).

The setup is a vpath build configured thus:

   ../pgsql/configure --enable-cassert --enable-debug
   --enable-integer-datetimes --with-perl --with-python --with-tcl
   --with-krb5 --with-includes=/usr/include/et --with-openssl
   --with-ldap --with-libxml --with-libxslt


Can anyone with a bit more make-fu than I have suggest why this should be so? Can we tweak the make files so hacks like this aren't required to get a fast build? Can anyone replicate this odd result?

cheers

andrew

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