5dfa003db5
The rdma-core library can map doorbell register in two ways, depending
on the environment variable "MLX5_SHUT_UP_BF":
- as regular cached memory, the variable is either missing or set to
zero. This type of mapping may cause the significant doorbell
register writing latency and requires an explicit memory write
barrier to mitigate this issue and prevent write combining.
- as non-cached memory, the variable is present and set to not "0"
value. This type of mapping may cause performance impact under
heavy loading conditions but the explicit write memory barrier is
not required and it may improve core performance.
The UAR creation function maps a doorbell in one of the above ways
according to the system. In run time, it always adds an explicit memory
barrier after writing to.
In cases where the doorbell was mapped as non-cached memory, the
explicit memory barrier is unnecessary and may impair performance.
The commit [1] solved this problem for a Tx queue. In run time, it
checks the mapping type and provides the memory barrier after writing to
a Tx doorbell register if it is needed. The mapping type is extracted
directly from the uar_mmap_offset field in the queue properties.
This patch shares this code between the drivers and extends the above
solution for each of them.
[1] commit
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| isal | ||
| mlx5 | ||
| octeontx | ||
| qat | ||
| zlib | ||
| meson.build | ||