在 2022/1/7 下午2:33, Xuan Zhuo 写道:
In the scenario where indirect is not used, each desc corresponds to an
extra, which is used to record information such as dma, flags, and
next.
In the scenario of using indirect, the assigned desc does not have the
corresponding extra record dma information, and the dma information must
be obtained from the desc when unmap.
This patch allocates the corresponding extra array when indirect desc is
allocated. This has these advantages:
1. Record the dma information of desc, no need to read desc when unmap
2. It will be more convenient and unified in processing
3. Some additional information can be recorded in extra, which will be
used in subsequent patches.
Two questions:
1) Is there any performance number for this change? I guess it gives
more stress on the cache.
2) Is there a requirement to mix the pre mapped sg with unmapped sg? If
not, a per virtqueue flag looks sufficient
Thanks
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