1 files changed, 111 insertions(+), 0 deletions(-)

A bench/profile.lua

@@ 0,0 1,111 @@
+#!/usr/bin/env tarantool
+-- One-off profiler over the 1 KB Person fixture — the size where the
+-- decode MB/s halves and the encode MB/s stops climbing. Uses jit.p
+-- (sampling profiler shipped with LuaJIT) so output points at the
+-- functions where wall time actually goes.
+--
+-- Usage:
+--   tarantool bench/profile.lua            -- full report
+--   tarantool bench/profile.lua encode     -- just encode
+--   tarantool bench/profile.lua decode     -- just decode
+
+package.path = './runtime/?.lua;./runtime/?/init.lua;'
+    .. './examples/expected/?.lua;./examples/expected/?/init.lua;'
+    .. package.path
+
+local jitp = require('jit.p')
+local clock = require('clock')
+
+local hello = require('full.hello.hello_pb')
+
+-- Same payload shape as bench.lua build_person_payload(1024).
+local per_email   = 36
+local fixed_bytes = 80
+local target      = 1024
+local n_emails    = math.max(1, math.floor((target - fixed_bytes) / per_email))
+local payload = {
+    name = 'bigbes',
+    age  = 42,
+    address = {street = '1 Main St', city = 'Springfield', zip = 12345},
+    lucky_numbers = {7, 13, 21, 42, 99},
+    emails = {},
+}
+for i = 1, n_emails do
+    payload.emails[i] = string.rep('e', 28) .. string.format('%04d', i)
+end
+
+local encoded = hello.Person_encode(payload)
+print(string.format('payload encoded size: %d bytes (%d emails)', #encoded, n_emails))
+
+-- Warmup so JIT compiles before sampling.
+for _ = 1, 5000 do hello.Person_encode(payload) end
+for _ = 1, 5000 do hello.Person_decode(encoded) end
+
+local ITER = 200000
+
+local function profile(label, fn)
+    print()
+    print(('=== %s — jit.p mode=fl,4 (function + line, 4ms sample) ==='):format(label))
+    -- 'fl' = group by function and line
+    -- '4' = sample every 4 ms (default 10 ms; we run for ~2 s so 4 ms gives ~500 samples)
+    -- '0' = no minimum count threshold
+    -- 'm0.5' = show entries with >= 0.5% of total
+    jitp.start('fl4m0.5')
+    local t0 = clock.monotonic64()
+    for _ = 1, ITER do fn() end
+    local elapsed = tonumber(clock.monotonic64() - t0) / 1e9
+    jitp.stop()
+    print(string.format('iters=%d  elapsed=%.3fs  msgs/s=%.0f',
+        ITER, elapsed, ITER / elapsed))
+end
+
+local function profile_v(label, fn)
+    print()
+    print(('=== %s — jit.p mode=vl,4 (full caller stack) ==='):format(label))
+    jitp.start('vl4m1')
+    for _ = 1, ITER do fn() end
+    jitp.stop()
+end
+
+local what = arg[1] or 'all'
+
+if what == 'all' or what == 'encode' then
+    profile('Person_encode (1KB)', function() hello.Person_encode(payload) end)
+    profile_v('Person_encode (1KB) callers', function() hello.Person_encode(payload) end)
+end
+
+if what == 'all' or what == 'decode' then
+    profile('Person_decode (1KB)', function() hello.Person_decode(encoded) end)
+    profile_v('Person_decode (1KB) callers', function() hello.Person_decode(encoded) end)
+end
+
+-- Also probe the encode-time intermediate string and table churn so we
+-- can attribute the 1.3 KB/op allocation to specific call sites.
+print()
+print('=== alloc breakdown (gcinfo delta over 50k iters with GC stopped) ===')
+
+local function alloc_for(label, fn)
+    collectgarbage('collect')
+    collectgarbage('stop')
+    local before = collectgarbage('count')
+    for _ = 1, 50000 do fn() end
+    local after = collectgarbage('count')
+    collectgarbage('restart')
+    collectgarbage('collect')
+    print(string.format('%-32s  %.1f B/op', label,
+        (after - before) * 1024 / 50000))
+end
+
+alloc_for('Person_encode (1KB)',    function() hello.Person_encode(payload) end)
+alloc_for('Person_decode (1KB)',    function() hello.Person_decode(encoded) end)
+
+-- Decode in pieces, to isolate the cost of repeated-string append.
+local wire = require('pb.wire')
+local emails_buf = string.char(0x1a, 32) .. string.rep('e', 32)  -- one email
+alloc_for('decode_string x26 (just the field)', function()
+    local list = {}
+    for i = 1, 26 do
+        local v, _ = wire.decode_string(emails_buf, 2)
+        list[#list + 1] = v
+    end
+end)