Fix nagle, other minor optimizations #8222
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Signed-off-by: Rusty Russell <[email protected]>
Our CORK logic was wrong, and it's better to use Nagle anyway: we disable Nagle just before sending timing-critical messages. Time for 100 (failed) payments: Before: 148.8573575 After: 10.7356977 Signed-off-by: Rusty Russell <[email protected]> Changelog-Fixed: Protocol: Removed 200ms latency from sending commit/revoke messages.
To run, use:
VALGRIND=0 TEST_BENCH=1 pytest tests/test_connection.py::test_bench
Example of running on my laptop (without --enable-debugbuild):
FAILED tests/test_connection.py::test_bench - assert 53.11918330192566 == 0
You can also run perf on l1 once it's running:
perf record --call-graph dwarf -q -p $(cat /tmp/ltests-*/test_bench_1/lightning-1/lightningd-regtest.pid)
Then ^C after 10 seconds and run "perf report".
Things which stand out:
1. Tracing in db_exec_prepared_v2:
31.12% 0.04% lightningd lightningd [.] db_exec_prepared_v2
- 31.08% db_exec_prepared_v2
+ 22.96% db_sqlite3_exec
+ 4.46% trace_span_end
+ 1.77% trace_span_start
+ 1.11% trace_span_tag
+ 0.72% tal_free
2. Logging:
- 16.03% logv
- 8.15% maybe_print
- log_to_files
+ 4.51% __GI__IO_fflush (inlined)
+ 1.97% tal_fmt_
+ 0.51% __GI___strftime_l (inlined)
3. Notification (when nothing is listening) in notify_log:
- 6.84% maybe_notify_log
- notify_log
+ 3.37% notify_send
+ 1.75% notify_start
+ 1.71% log_notification_serialize
0.56% new_log_entry
Signed-off-by: Rusty Russell <[email protected]>
…hecking. Before: 92.26076173782349 91.9576666355133 90.92732524871826 After: 90.5989830493927 88.10309219360352 90.07689118385315
Signed-off-by: Rusty Russell <[email protected]>
If nobody is subscribed, have notify_start return NULL and the caller can skip serialization. This is particularly useful for the "log" notification which can get called a lot. Signed-off-by: Rusty Russell <[email protected]>
This means we don't have to iterate through all plugins, making our "do we even have to construct this notification" optimization much more efficient. Signed-off-by: Rusty Russell <[email protected]>
This speeds logging slightly, but most of the time is actually spent in fflush() (which we need). Result: FAILED tests/test_connection.py::test_bench - assert 51.54966354370117 == 0 Signed-off-by: Rusty Russell <[email protected]>
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I noticed we were not going as fast as we should, in a 100-payments test. Turns out our Nagle-suppressing code was wrong!
Then I continued with minor optimization until our profiling basically only contained sqlite operations.