[Bug 1894453] Re: Building Ceph packages with RelWithDebInfo

[Corey Bryant]

@Ponnuvel, I'm not fully familiar with how ceph deals with rocksdb code
so this is mostly observations from my end.

Specifically looking at 15.2.4 for groovy. In
https://github.com/ceph/ceph/tree/v15.2.4/src, it appears to pick up
rocksdb from a specific commit (rocksdb @ e24b452) that exists in ceph's
forked rocksdb repo (https://github.com/ceph/rocksdb @ ceph-
octopus-v5.8-1436). The commit for ac304ad doesn't appear to exist in
the forked repo, but does exist in the fb repo at
https://github.com/facebook/rocksdb/.

I'm not sure what the process is but it seems that ac304ad needs to get
into ceph's forked repo. Perhaps a cherry-pick with a PR is enough.
James probably knows the process.

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https://bugs.launchpad.net/bugs/1894453

Title:
  Building Ceph packages with RelWithDebInfo

Status in ceph package in Ubuntu:
  In Progress

Bug description:
  This is to consider/discuss the possibility of whether the Ceph
  packages (UCA) should be built with RelWithDebInfo build option
  (CMAKE_BUILD_TYPE [0]) which can be supplied to the build script
  do_cmake.sh [1].

  Currently, Upstream as well as UCA builds default to 'Debug' [0]
  builds. But is any reason why shouldn't go for RelWithDebInfo (i.e.
  "Release with Debug information")?

  
  There's one issue noted with RelWithDebInfo which has a workaround too [2].

  In general, gcc's -O2 [3] build should generate better code as well as
  there's a specific case for Ceph [4] that it improves performance.

  [0] https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html

  [1] https://github.com/ceph/ceph/blob/master/do_cmake.sh

  [2] https://docs.ceph.com/docs/master/dev/perf/#common-issues

  [3] https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

  [4] https://bugs.gentoo.org/show_bug.cgi?id=733316

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