KNI supposes that mbufs are contiguous in kernel virtual memory. This
may not be true when using the IOVA=VA mode. To fix this, a possibility
is to ensure that objects do not cross page boundaries in mempool. This
patchset implements this in the last patch (5/5).
The previous patches prepare the job:
- allow to populate with an unaligned virtual area (1/5).
- reduce spaced wasted in the mempool size calculation when not using
the iova-contiguous allocation (2/5).
- remove the iova-contiguous allocation when populating mempool (3/5):
a va-contiguous alloc does the job as well if we want to populate
without crossing page boundaries, so simplify the mempool populate
function.
- export a function to get the minimum page used in a mempool (4/5)
Memory consumption impact when using hugepages:
- worst case: + ~0.1% for a mbuf pool (objsize ~= 2368)
- best case: -50% for if pool size is just above page size
The memory consumption impact with 4K pages in IOVA=VA mode could
however consume up to 75% more memory for mbuf pool, because there will
be only 1 mbuf per page. Not sure how common this usecase is.
Caveat: this changes the behavior of the mempool (calc_mem_size and
populate), and there is a small risk to break things, especially with
alternate mempool drivers.
rfc -> v1
* remove first cleanup patch, it was pushed separately
a2b5a8722f20 ("mempool: clarify default populate function")
* add missing change in rte_mempool_op_calc_mem_size_default()
* allow unaligned addr/len in populate virt
* better split patches
* try to better explain the change
* use DPDK align macros when relevant
Olivier Matz (5):
mempool: allow unaligned addr/len in populate virt
mempool: reduce wasted space on mempool populate
mempool: remove optimistic IOVA-contiguous allocation
mempool: introduce function to get mempool page size
mempool: prevent objects from being across pages
lib/librte_mempool/rte_mempool.c | 140 +++++++------------
lib/librte_mempool/rte_mempool.h | 12 +-
lib/librte_mempool/rte_mempool_ops.c | 4 +-
lib/librte_mempool/rte_mempool_ops_default.c | 57 ++++++--
lib/librte_mempool/rte_mempool_version.map | 1 +
5 files changed, 114 insertions(+), 100 deletions(-)
--
2.20.1
