Re: [PATCH v2 2/2] virtio-ring: Allocate indirect buffers from cache when possible

Il 06/09/2012 07:02, Michael S. Tsirkin ha scritto:

quoted

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It might be worth just unconditionally having a cache for the 2
descriptor case.  This is what I get with qemu tap, though for some
reason the device features don't have guest or host CSUM, so my setup is
probably screwed:

Yes without checksum net core always linearizes packets, so yes it is
screwed.
For -net, skb always allocates space for 17 frags + linear part so
it seems sane to do same in virtio core, and allocate, for -net,
up to max_frags + 1 from cache.
We can adjust it: no _SG -> 2 otherwise 18.

Not sure about other drivers, maybe really use 2 there for now.

2 should also be good for virtio-blk and virtio-scsi 4KB random rw
workloads.

Paolo