A mempool consumes 3 memzones (with the default ring mempool driver).
The default DPDK configuration allows RTE_MAX_MEMZONE (2560) memzones.
Assuming there is no other memzones that means that we can have a
maximum of 853 mempools.
In the vhost library, the IOTLB cache code so far was requesting a
mempool per vq, which means that at the maximum, the vhost library
could request mempools for 426 qps.
This limit was recently reached on big systems with a lot of virtio
ports (and multiqueue in use).
While the limit on mempool count could be something we fix at the DPDK
project level, there is no reason to use mempools for the IOTLB cache:
- the IOTLB cache entries do not need to be DMA-able and are only used
by the current process (in multiprocess context),
- getting/putting objects from/in the mempool is always associated with
some other locks, so some level of lock contention is already present,
We can convert to a malloc'd pool with objects put in a free list
protected by a spinlock.
Signed-off-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
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