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optimize ReadBatch by moving memory allocation outside the loop rang…
My use case is reading and processing lots of UDP multicast data ~ 3.5Gbps, over 2M Packets per second. This being UDP, the kernel will deliver one packet per buffer. (GRO helps, but not much) Using ReadBatch from golang.org/x/net/ipv4 should reduce syscall overhead. Benchmarking this, I found that is slower than just using Read() The current implementation of mmsghdr.pack() does allocate slices for every buffer in the inner loop, which, at a rate of 3M pps, is a big performance limit. ( Side note: Even with this patch, ReadBatch is only a win if there is enough data to read in each call. In a tight loop, where only a few buffers are returned in each call, the overhead involved will make things worse than just using Read().)
Changes: Simply moving the allocation out of the innermost loop will reduce the allocations by a significant amount if len(Messages) is large
Downsides: Slightly less efficient with very small BatchLengths. But in this case, ReadBatch is already quite inefficient and should not be used
Further work: There are still allocations for every call in ReadBatch, which is unnecessary. Changing this will need interface changes, because system specific data (iovec etc) needs to be stored somewhere.
This PR (HEAD: 415bc559122efb83ac80c5067d1bc37d2dbb7e0f) has been imported to Gerrit for code review.
Please visit https://go-review.googlesource.com/c/net/+/245162 to see it.
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Message from Go Bot:
Patch Set 1:
Congratulations on opening your first change. Thank you for your contribution!
Next steps: A maintainer will review your change and provide feedback. See https://golang.org/doc/contribute.html#review for more info and tips to get your patch through code review.
Most changes in the Go project go through a few rounds of revision. This can be surprising to people new to the project. The careful, iterative review process is our way of helping mentor contributors and ensuring that their contributions have a lasting impact.
During May-July and Nov-Jan the Go project is in a code freeze, during which little code gets reviewed or merged. If a reviewer responds with a comment like R=go1.11 or adds a tag like "wait-release", it means that this CL will be reviewed as part of the next development cycle. See https://golang.org/s/release for more details.
Please don’t reply on this GitHub thread. Visit golang.org/cl/245162. After addressing review feedback, remember to publish your drafts!
howdy @jdeisenh! :smile: I believe this was solved in https://github.com/golang/net/commit/f8dd838d8c7de318b0734b3f1afa78a9d976bf09, so this can maybe be closed?
(a bit impolite that your PR wasn't even answered :unamused:)
