On 7/19/19 4:38 PM, Olivier Matz wrote:
When IOVA mode is VA, a mempool can be created with objects that
are not physically contiguous, which breaks KNI.
To solve this, this patchset changes the default behavior of mempool
populate function, to prevent objects from being located across pages.
I'll provide top level review notes on individual patches, but what
I don't understand in general, why do we add a rule to respect
page boundaries in any case even when it is not absolutely required.
It may add holes. Can it make negative impact on performance?
I think that KNI VA-mode requirements are very specific.
It is VA-mode, but page boundaries should be respected even
if VA is contiguous.
Olivier Matz (4):
mempool: clarify default populate function
mempool: unalign size when calculating required mem amount
mempool: introduce function to get mempool page size
mempool: prevent objects from being across pages
lib/librte_mempool/rte_mempool.c | 106 +++++++++++----------------
lib/librte_mempool/rte_mempool.h | 8 +-
lib/librte_mempool/rte_mempool_ops.c | 4 +-
lib/librte_mempool/rte_mempool_ops_default.c | 39 +++++++++-
4 files changed, 90 insertions(+), 67 deletions(-)
---
Hi,
@Olivier,
Any suggestions..?
I took some time to go a bit deeper. I still think we can change the
default behavior to avoid objects to be located accross pages. But
it is more complex that I expected.
I made a draft patchset, that, in short:
- cleans/renames variables
- removes the optimistic full iova contiguous allocation
- changes return value of calc_mem_size to return the unaligned size,
therefore the allocation is smaller in case of big hugepages
- changes rte_mempool_op_populate_default() to prevent allocation
of objects accross multiple pages
Andrew, Anatoly, did I miss something?
Vamsi, can you check if it solves your issue?
Anyway, even if validate the patchset it and make it work, I'm afraid
this is not something that could go in 19.08.
The only alternative I see is a specific mempool allocation function
when used in iova=va mode + kni, as you proposed previously.
It can probably be implemented without adding a flag, starting from
rte_mempool_create(), and replacing rte_mempool_populate_default(mp) by
something else: allocate pages one by one, and call
rte_mempool_populate_iova() for each of them.
Hope it helps. Unfortunately, I may not have too much time to spend on
it in the coming days.
Regards,
Olivier
