On 2019/10/11 下午9:45, Michael S. Tsirkin wrote:
So the idea is as follows: we convert descriptors to an
independent format first, and process that converting to
iov later.
The point is that we have a tight loop that fetches
descriptors, which is good for cache utilization.
This will also allow all kind of batching tricks -
e.g. it seems possible to keep SMAP disabled while
we are fetching multiple descriptors.
I wonder this may help for performance:
- another indirection layer, increased footprint
- won't help or even degrade when there's no batch
- an extra overhead in the case of in order where we should already had
tight loop
- need carefully deal with indirect and chain or make it only work for
packet sit just in a single descriptor
Thanks
And perhaps more importantly, this is a very good fit for the packed
ring layout, where we get and put descriptors in order.
This patchset seems to already perform exactly the same as the original
code already based on a microbenchmark. More testing would be very much
appreciated.
Biggest TODO before this first step is ready to go in is to
batch indirect descriptors as well.
Integrating into vhost-net is basically
s/vhost_get_vq_desc/vhost_get_vq_desc_batch/ -
or add a module parameter like I did in the test module.
Michael S. Tsirkin (2):
vhost: option to fetch descriptors through an independent struct
vhost: batching fetches
drivers/vhost/test.c | 19 ++-
drivers/vhost/vhost.c | 333 +++++++++++++++++++++++++++++++++++++++++-
drivers/vhost/vhost.h | 20 ++-
3 files changed, 365 insertions(+), 7 deletions(-)
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