Messages in this thread | | | Date | Wed, 10 Sep 2014 17:18:23 +0200 | From | Paolo Bonzini <> | Subject | Re: [PATCH] virtio_blk: merge S/G list entries by default |
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Il 07/09/2014 12:32, Ming Lei ha scritto: > It is a good idea to disable SG merge for vq incapable of indirect because > there are very limited direct descriptors.
I think you mean _enabling_ SG merge if indirect descriptors are not there.
> For vq capable of indirect, it should be better to not do SG merge at default > because: > > - from hypervisor view, no matter how many segments one req has, all are > submitted to host kernel by one syscall, such as readv/io_submit > > - host kernel still need to do the same merge again
Here we agree.
Paolo
> From my test(virtio-blk over null_blk), looks enabling SG merge may cause > throughput a little drop(~3%).
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