Recently, coordinator_result was introduced as an alternative for
exceptions. It was placed in the main "exceptions/exceptions.hh" header,
which virtually every single source file in Scylla includes.
But unfortunately, it brings in some heavy header files and templates,
leading to a lot of wasted build time - ClangBuildAnalyzer measured that
we include exceptions.hh in 323 source files, taking almost two seconds
each on average.
In this patch, we split the coordinator_result feature into a separate
header file, "exceptions/coordinator_result", and only the few places
which need it include the header file. Unfortunately, some of these
few places are themselves header, so the new header file ends up being
included in 100 source files - but 100 is still much less than 323 and
perhaps we can reduce this number 100 later.
After this patch, the total Scylla object-file size is reduced by 6.5%
(the object size is a proxy for build time, which I didn't directly
measure). ClangBuildAnalyzer reports that now each of the 323 includes
of exceptions.hh only takes 80ms, coordinator_result.hh is only included
100 times, and virtually all the cost to include it comes from Boost's
result.hh (400ms per inclusion).
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220228204323.1427012-1-nyh@scylladb.com>
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