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@camshaft camshaft commented Jul 11, 2023

Description of changes:

While using the probes from #1866, I noticed that the sendmmsg syscall could take quite a long time (upwards of 1ms), especially when the total number of messages being sent was high.

One thing that did help was to use the multithreaded runtime and multiple TX sockets. This does increase CPU usage but also increases throughput and minimizes latency, since we're executing multiple syscalls in parallel, each with smaller buffers.

Call-outs:

I've made this an unstable option for now, in case we want to change how the socket initialization works. Currently, it just calls try_clone() on the single socket for each task, which might cause issues later down the line (not sure).

Testing:

$ S2N_QUIC_UNSTABLE_TX_SOCKET_COUNT=16 s2n-quic-qns perf server --port 4433 --stats --multithread

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

@camshaft camshaft marked this pull request as ready for review July 11, 2023 18:56
@camshaft camshaft requested a review from WesleyRosenblum July 13, 2023 17:16
@camshaft camshaft merged commit 2499439 into main Jul 13, 2023
@camshaft camshaft deleted the camshaft/multi-socket branch July 13, 2023 21:48
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2 participants