[QGIS-Developer] expected ccache hit ratio on new micro release?

[Greg Troxel]

(If people feel this query belongs on -user, please feel free to tell
me that.)

I maintain the qgis entry in pkgsrc, a multi-OS multi-CPU packaging
system, and use qgis 3.16.x on NetBSD.  So I am talkiing below about
NetBSD 9 amd64.

I use ccache, to save compilation time, since in doing packaging I am
often rebuilding X that depends on updated Y, but most of X's
compilations are the same headers and sources.  And, I often rebuild a
package after I just built it, to verify I didn't break something, after
making a minor change to the packaging files.

On September 5, I updated the package to 3.16.10 (was behind for no good
reason).  I always build, make a package, install it, and then run qgis
from the installed package before pushing the update to the rest of
pkgsrc.  So far, it's been smooth, and qgis seems not to have any
NetBSD-specific issues.

Just now I changed the version in the control file to 3.16.11 and am
building.  I zeroed stats before and have done only a tiny bit of other
building.  So far, ccache reports:

  cache directory                     /home/gdt/.ccache
  primary config                      /home/gdt/.ccache/ccache.conf
  secondary config      (readonly)    /usr/pkg/etc/ccache.conf
  stats updated                       Wed Sep 15 13:16:01 2021
  stats zeroed                        Wed Sep 15 09:17:16 2021
  cache hit (direct)                    13
  cache hit (preprocessed)              80
  cache miss                          4056
  cache hit rate                      2.24 %
  called for link                       94
  called for preprocessing            2101
  compile failed                        14
  preprocessor error                    26
  autoconf compile/link                106
  no input file                         24
  cleanups performed                     4
  files in cache                    206471
  cache size                           9.0 GB
  max cache size                      10.0 GB

This means qgis will take about 8h to build, on a machine that was
fairly high end in 2014, with 1 core in use (for heat), and plenty of
RAM.  This matches my memory of previous updates.

It surprises me that a bug fix release would have almost hits, but
perhaps there is a version number in a header that every program reads,
and thus every file misses.  But I am not arguing that it is a bug, of
course.

I am curious if anyone else uses ccache, and if this is what they see as
well.

Thanks,
Greg
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