From: Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>, Igor Munkin <imun@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: [Tarantool-patches] [PATCH] lua: refactor port_lua_do_dump and encode_lua_call Date: Fri, 18 Jun 2021 21:14:16 +0300 [thread overview] Message-ID: <20210618181416.25454-1-skaplun@tarantool.org> (raw) The old code flow was the following: 1) `struct port_lua` given to `port_lua_do_dump()` has Lua stack with arguments to encode to MessagePack 2) The main coroutine `tarantool_L` is used with `lua_cpcall()` to call `encode_lua_call_16()` or `encode_lua_call()` 3) Objects on minor coroutine are encoded via `luamp_encode_call16()` or `luamp_encode()`. This encoding may raise an error on unprotected `port->L` coroutine. This coroutine has no protected frame on it and this call should fail in pure Lua. It is forbidden to call anything on unprotected coroutine [1] (Lua 5.1 sets protection only for specific lua_State [2] and calls a panic function if we raise an error on unprotected lua_State [3]). Netherless, there is no panic at now due to two facts. The first one is LuaJIT's support of C++ exception handling [4] that allows to raise an error in Lua and catch it in C++ or vice versa. But documentation still doesn't permit errors on unprotected coroutines (at least we must set try-catch block). The second one is double monkey-patching of LuaJIT to restore currently executed coroutine, when C function or fast function raises an error [5][6] (see related issue here [7][8]). For these reasons, when an error occurs, the unwinder searches and finds the C-protected stack frame from the `lua_cpcall()` for the `tarantool_L` coroutine and unwinds until that point (without aforementioned patches LuaJIT just calls a panic function and exit). 4) If an error is raised, and `lua_cpcall()` returns not `LUA_OK`, then the error from `port->L` coroutine is converted into a Tarantool error and a diagnostic is set. The auxiliary usage of `tarantool_L` coroutine is redundant and doesn't respect Lua idiomatic of usage. So this patch drops it and uses only minor coroutine instead with `lua_pcall()`. Functions to encode are saved as entrance in the `LUA_REGISTRY` table to reduce GC pressure, like it is done for other handlers [9]. [1]: https://www.lua.org/manual/5.2/manual.html#4.6 > If an error happens outside any protected environment, Lua calls a > panic function [2]: https://www.lua.org/source/5.1/lstate.h.html#lua_State [3]: https://www.lua.org/source/5.1/ldo.c.html#luaD_throw [4]: https://luajit.org/extensions.html#exceptions [5]: https://github.com/tarantool/luajit/commit/ed412cd9f55fe87fd32a69c86e1732690fc5c1b0 [6]: https://github.com/tarantool/luajit/commit/97699d9ee2467389b6aea21a098e38aff3469b5f [7]: https://github.com/tarantool/tarantool/issues/1516 [8]: https://www.freelists.org/post/luajit/Issue-with-PCALL-in-21 [9]: https://github.com/tarantool/tarantool/commit/e88c0d21ab765d4c53bed2437c49d77b3ffe4216 --- Branch: https://github.com/tarantool/tarantool/tree/skaplun/gh-noticket-refactor-lua-call See the benchmarks sources here [1]. Before patch: | Encode map: 189851357 mcs, 15.8 K ps | Encode seq: 187926351 mcs, 16.0 K ps | Encode str: 185451675 mcs, 16.2 K ps | Encode dig: 184833396 mcs, 16.2 K ps After patch: | Encode map: 187814261 mcs, 16.0 K ps | Encode seq: 183755028 mcs, 16.3 K ps | Encode str: 181571626 mcs, 16.5 K ps | Encode dig: 181572998 mcs, 16.5 K ps Looks like the perf doesn't degrade at least. [1]: https://gist.github.com/Buristan/3e6d6bf2c722874bec55a8c5a44b98f3 src/box/lua/call.c | 71 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 56 insertions(+), 15 deletions(-) diff --git a/src/box/lua/call.c b/src/box/lua/call.c index 0315e720c..3b2572096 100644 --- a/src/box/lua/call.c +++ b/src/box/lua/call.c @@ -61,6 +61,8 @@ enum handlers { HANDLER_CALL, HANDLER_CALL_BY_REF, HANDLER_EVAL, + HANDLER_ENCODE_CALL, + HANDLER_ENCODE_CALL_16, HANDLER_MAX, }; @@ -400,11 +402,26 @@ struct encode_lua_ctx { struct mpstream *stream; }; +/** + * Encode call results to msgpack from Lua stack. + * Lua stack has the following structure -- the last element is + * lightuserdata pointer to encode_lua_ctx, all other values are + * arguments to proceed. + * The function encodes all given Lua objects to msgpack stream + * from context, sets port's size and returns no value on the Lua + * stack. + * XXX: This function *MUST* be called under lua_pcall(), because + * luamp_encode() may raise an error. + */ static int encode_lua_call(lua_State *L) { + assert(lua_islightuserdata(L, -1)); struct encode_lua_ctx *ctx = - (struct encode_lua_ctx *) lua_topointer(L, 1); + (struct encode_lua_ctx *) lua_topointer(L, -1); + assert(ctx->port->L == L); + /* Delete ctx from the stack. */ + lua_pop(L, 1); /* * Add all elements from Lua stack to the buffer. * @@ -413,33 +430,48 @@ encode_lua_call(lua_State *L) struct luaL_serializer *cfg = luaL_msgpack_default; const struct serializer_opts *opts = ¤t_session()->meta.serializer_opts; - int size = lua_gettop(ctx->port->L); + const int size = lua_gettop(L); for (int i = 1; i <= size; ++i) - luamp_encode(ctx->port->L, cfg, opts, ctx->stream, i); + luamp_encode(L, cfg, opts, ctx->stream, i); ctx->port->size = size; mpstream_flush(ctx->stream); return 0; } +/** + * Encode call_16 results to msgpack from Lua stack. + * Lua stack has the following structure -- the last element is + * lightuserdata pointer to encode_lua_ctx, all other values are + * arguments to proceed. + * The function encodes all given Lua objects to msgpack stream + * from context, sets port's size and returns no value on the Lua + * stack. + * XXX: This function *MUST* be called under lua_pcall(), because + * luamp_encode() may raise an error. + */ static int encode_lua_call_16(lua_State *L) { + assert(lua_islightuserdata(L, -1)); struct encode_lua_ctx *ctx = - (struct encode_lua_ctx *) lua_topointer(L, 1); + (struct encode_lua_ctx *) lua_topointer(L, -1); + /* Delete ctx from the stack. */ + lua_pop(L, 1); + assert(ctx->port->L == L); /* * Add all elements from Lua stack to the buffer. * * TODO: forbid explicit yield from __serialize or __index here */ struct luaL_serializer *cfg = luaL_msgpack_default; - ctx->port->size = luamp_encode_call_16(ctx->port->L, cfg, ctx->stream); + ctx->port->size = luamp_encode_call_16(L, cfg, ctx->stream); mpstream_flush(ctx->stream); return 0; } static inline int port_lua_do_dump(struct port *base, struct mpstream *stream, - lua_CFunction handler) + enum handlers handler) { struct port_lua *port = (struct port_lua *) base; assert(port->vtab == &port_lua_vtab); @@ -450,13 +482,20 @@ port_lua_do_dump(struct port *base, struct mpstream *stream, struct encode_lua_ctx ctx; ctx.port = port; ctx.stream = stream; - struct lua_State *L = tarantool_L; - int top = lua_gettop(L); - if (lua_cpcall(L, handler, &ctx) != 0) { - luaT_toerror(port->L); + lua_State *L = port->L; + /* + * At the moment Lua stack holds only values to encode. + * Insert corresponding encoder to the bottom and push + * encode context as lightuserdata to the top. + */ + const int size = lua_gettop(L); + lua_rawgeti(L, LUA_REGISTRYINDEX, execute_lua_refs[handler]); + assert(lua_isfunction(L, -1) && lua_iscfunction(L, -1)); + lua_insert(L, 1); + lua_pushlightuserdata(L, &ctx); + /* nargs -- all arguments + lightuserdata. */ + if (luaT_call(L, size + 1, 0) != 0) return -1; - } - lua_settop(L, top); return port->size; } @@ -467,7 +506,7 @@ port_lua_dump(struct port *base, struct obuf *out) struct mpstream stream; mpstream_init(&stream, out, obuf_reserve_cb, obuf_alloc_cb, luamp_error, port->L); - return port_lua_do_dump(base, &stream, encode_lua_call); + return port_lua_do_dump(base, &stream, HANDLER_ENCODE_CALL); } static int @@ -477,7 +516,7 @@ port_lua_dump_16(struct port *base, struct obuf *out) struct mpstream stream; mpstream_init(&stream, out, obuf_reserve_cb, obuf_alloc_cb, luamp_error, port->L); - return port_lua_do_dump(base, &stream, encode_lua_call_16); + return port_lua_do_dump(base, &stream, HANDLER_ENCODE_CALL_16); } static void @@ -501,7 +540,7 @@ port_lua_get_msgpack(struct port *base, uint32_t *size) mpstream_init(&stream, region, region_reserve_cb, region_alloc_cb, luamp_error, port->L); mpstream_encode_array(&stream, lua_gettop(port->L)); - int rc = port_lua_do_dump(base, &stream, encode_lua_call); + int rc = port_lua_do_dump(base, &stream, HANDLER_ENCODE_CALL); if (rc < 0) { region_truncate(region, region_svp); return NULL; @@ -1049,6 +1088,8 @@ box_lua_call_init(struct lua_State *L) [HANDLER_CALL] = execute_lua_call, [HANDLER_CALL_BY_REF] = execute_lua_call_by_ref, [HANDLER_EVAL] = execute_lua_eval, + [HANDLER_ENCODE_CALL] = encode_lua_call, + [HANDLER_ENCODE_CALL_16] = encode_lua_call_16, }; for (int i = 0; i < HANDLER_MAX; i++) { -- 2.31.0
next reply other threads:[~2021-06-18 18:15 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-18 18:14 Sergey Kaplun via Tarantool-patches [this message] 2021-06-21 20:36 ` Vladislav Shpilevoy via Tarantool-patches 2021-06-22 13:38 ` Sergey Kaplun via Tarantool-patches 2021-06-24 20:00 ` Vladislav Shpilevoy via Tarantool-patches 2021-06-29 7:07 ` Sergey Kaplun via Tarantool-patches 2021-08-01 12:34 ` Igor Munkin via Tarantool-patches 2021-08-02 14:25 ` Sergey Kaplun via Tarantool-patches 2021-08-12 17:35 ` Igor Munkin via Tarantool-patches 2021-08-13 7:30 ` Sergey Kaplun via Tarantool-patches 2021-08-13 7:41 ` Vitaliia Ioffe via Tarantool-patches 2021-08-13 9:27 ` Sergey Kaplun via Tarantool-patches 2021-08-04 22:29 ` Vladislav Shpilevoy via Tarantool-patches 2021-08-14 10:16 ` Igor Munkin via Tarantool-patches
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