[libvirt] [libvirt PATCH v3 0/4] Share cgroup code that is duplicated between QEMU and LXC

[Pavel Hrdina]

On Thu, Sep 13, 2018 at 09:48:10AM +0200, Fabiano Fidêncio wrote:
> virLXCCgroupSetupBlkioTune() and qemuSetupBlkioCgroup() and
> virLXCCgroupSetupCpuTune() and qemuSetupCpuCgroup() are the most similar
> functions between QEMU and LXC code.
> 
> Let's move their common code to virCgroup.
> 
> Mind that the first two patches are basically preparing the ground for
> the changes introduced in the last two patches.
> 
> I know that Pavel Hrdina suggested taking a different path[0] for this
> series but I do believe Michal's and Jano's points are valid, thus I've
> decided to just do the changes suggested by Michal (at least for now).

That's OK, but I'm still not convinced that vircgroup.c is the correct
place.  These new functions convert some data structure into multiple
cgroup API calls.

By that logic we could do the same for virTypedParams which would lead
into adding several helpers that would covert data structures into
virTypedParams and that feels wrong.

Another thing that I don't like is moving the blkio and mem tune code
into src/util because in util we have helpers to work with OS tools
or OS related data and some really generic tools that could be easily
used outside of libvirt and virtualization related code (yes, there are
some exception that should be most likely fixed).

If we want to deduplicate qemu_cgroup.c and lxc_cgroup.c we should
introduce src/conf/domain_cgroup.c where we would place all common
domain related code that configure cgroups.

Pavel

> 
> [0]: https://www.redhat.com/archives/libvir-list/2018-September/msg00534.html
> 
> changes since v1:
> - Michal Privoznik pointed out (as did the `make syntax-check` :-)) that
>   we do want to keep src/util independently of the parsing code (thus,
>   including "conf/domain_conf.h" in vircgroup.h is not the way to go).
>   This has been solved now by partially following Michal's suggestion
>   and splitting the structs and functions that would be use in the
>   common code to new different files.
> 
> changes since v2:
> - Fixed `make syntax-check` errors that I've missed before (didn't have
>   cppi installed);
> - Created a new section in src/libvirt_private.syms to correctly export
>   the virBlkioDeviceArrayClear symbol;
> - Removed a virlkio.c from libvirt_setuid_rpc_client_la__SOURCES (why
>   did I add it there in the first place? ;-))
> - Explicitly included virmem.h in qemu_{domain,command}.c.
>   Although there's nothing enforcing it, I do believe it's a good
>   practive that should be followed and I've checked with Andrea and
>   Peter about doing that and both agreed with the approach.
> 
> 
> Fabiano Fidêncio (4):
>   domain_conf: split out virBlkioDevice and virDomainBlkiotune
>     definitions
>   domain_conf: split out virDomainMemtune and virDomainHugePage
>     definitions
>   vircgroup: Add virCgroupSetupBlkioTune()
>   vircgroup: Add virCgroupSetupMemTune()
> 
>  src/conf/domain_conf.c   | 22 ++++--------
>  src/conf/domain_conf.h   | 70 +++----------------------------------
>  src/libvirt_private.syms |  7 +++-
>  src/lxc/lxc_cgroup.c     | 69 ++-----------------------------------
>  src/qemu/qemu_cgroup.c   | 61 ++-------------------------------
>  src/qemu/qemu_command.c  |  5 +--
>  src/qemu/qemu_domain.c   |  3 +-
>  src/util/Makefile.inc.am |  2 ++
>  src/util/virblkio.c      | 37 ++++++++++++++++++++
>  src/util/virblkio.h      | 52 ++++++++++++++++++++++++++++
>  src/util/vircgroup.c     | 74 ++++++++++++++++++++++++++++++++++++++++
>  src/util/vircgroup.h     |  5 +++
>  src/util/virmem.h        | 66 +++++++++++++++++++++++++++++++++++
>  13 files changed, 263 insertions(+), 210 deletions(-)
>  create mode 100644 src/util/virblkio.c
>  create mode 100644 src/util/virblkio.h
>  create mode 100644 src/util/virmem.h
> 
> -- 
> 2.17.1
> 
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> 
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