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由 Mark McLoughlin 提交于
On reflection, perhaps it does make sense to set a default value for the sndbuf= tap parameter. For best effect, sndbuf= should be set to just below the capacity of the physical NIC. Setting it higher will cause packets to be dropped before the limit is hit. Setting it much lower will not cause any problems unless you set it low enough such that the guest cannot queue up new packets before the NIC has emptied its queue. In Linux, txqueuelen=1000 by default for ethernet NICs. Given a 1500 byte MTU, 1Mb is a good choice for sndbuf. If it turns out that txqueuelen is actually much lower than this, then sndbuf is essentially disabled. In the event that txqueuelen is much higher, it's unlikely that the NIC will be able to empty a 1Mb queue. Thanks to Herbert Xu for this logic. Signed-off-by: NMark McLoughlin <markmc@redhat.com> Cc: Herbert Xu <herbert.xu@redhat.com> Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
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