Shard pure-serve across cores

A burst now looks at the store once (pure_store_pin) instead of once per
request; another shard's commit ends before its answer is sent, so a
request made after that answer still reads it. With this alone one thread
serves 125k small keep-alive reads per second, as many as axum on three
cores, with a shorter p99.

--threads N runs a shard per thread: its own SO_REUSEPORT listener, epoll
set, runtime domain, app and store handle. Writer sessions of the tree
store now take turns inside a process with a mutex (the file lock belongs
to the process and does not keep threads apart), and revisions settle
concurrent edits of a key. A module with states runs on one thread. Three
shards serve 151k reads per second; they still commit one by one, so
durable writes and 1 MiB reads are better on one thread for now, which
stays the default. Note 075 records the numbers.

1 files changed, 2 insertions, 0 deletions

diff --git a/benchmarks/http/run.py b/benchmarks/http/run.py
index 96f4bc0..8ce1474 100644
--- a/benchmarks/http/run.py
+++ b/benchmarks/http/run.py
@@ -72,6 +72,8 @@ def main():
                                    '--store', d, '--port', '0', '--budget', str(args.budget)],
         'pure-serve': lambda d: [PURE / 'build/pure-serve', '--module', args.module, '--store', d, '--port', '0',
                                  '--budget', str(args.budget)],
+        'pure-serve-3': lambda d: [PURE / 'build/pure-serve', '--module', args.module, '--store', d, '--port', '0',
+                                   '--budget', str(args.budget), '--threads', '3'],
         'axum-memory': lambda d: [axum, '--port', '0'],
         'axum-durable': lambda d: [axum, '--port', '0', '--durable', d],
         'axum-atomic': lambda d: [axum, '--port', '0', '--atomic', d],