[libvirt] [PATCH 1/2] rpc: Switch to dynamically allocated message buffer

[Eric Blake]

On 04/27/2012 07:22 AM, Michal Privoznik wrote:
> Currently, we are allocating buffer for RPC messages statically.
> This is not such pain when RPC limits are small. However, if we want
> ever to increase those limits, we need to allocate buffer dynamically,
> based on RPC message len (= the first 4 bytes). Therefore we will
> decrease our mem usage in most cases and still be flexible enough in
> corner cases.
> ---
>  src/rpc/virnetclient.c       |   16 ++-
>  src/rpc/virnetmessage.c      |   12 ++-
>  src/rpc/virnetmessage.h      |    6 +-
>  src/rpc/virnetserverclient.c |   20 ++-
>  tests/virnetmessagetest.c    |  393 +++++++++++++++++++++++-------------------
>  5 files changed, 264 insertions(+), 183 deletions(-)

I haven't looked closely at this, but I do have a generic question:

Are you malloc'ing and free'ing the buffer for each rpc on every call,
or are you tracking a pool of buffers and only alloc'ing when needed?
Furthermore, can you use the stack or a statically allocated array to
receive short messages, saving alloc only for the long messages?  I'm
worried about performance if we malloc on every single RPC call.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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