The current implementation of iobuf_pool has two problems:
- prealloc of 12.5MB memory, this limits the scale factor of the gluster
processes due to RAM requirements
- lock contention, as the current implementation has one global
iobuf_pool lock. Credits for debugging and addressing the same goes to
Krutika Dhananjay <kdhananj@redhat.com>. Issue: #410
Hence changing the iobuf implementation to use per thread mem pool.
This may theoritically appear to cause perf dip as there is no preallocation.
But per thread mem pool will not have significant perf impact as the last
allocated memory is kept alive for subsequent allocs, for some time.
The worst case would be if iobufs requested are of random sizes each time.
The best case is, if we get iobuf request of the same size. From the perf
tests, this patch did not seem to cause any perf decrease.
Note that, with this patch, the rdma performance is going to degrade
drastically. In one of the previous patchsets we had fixes to not
degrade rdma perf, but rdma is not supported and also not tested [1].
Hence the decision was to not have code in rdma that is not tested
and not supported.
[1] https://lists.gluster.org/pipermail/gluster-users.old/2018-July/034400.html
Updates: #325
Change-Id: Ic2ef3bd498f9250dea25f25ba0c01fde19584b27
Signed-off-by: Poornima G <pgurusid@redhat.com>