On Dec 18, 2012, at 2:29 AM, Igor Galić <i.ga...@brainsware.org> wrote:
> > > ----- Original Message ----- >> Hi all, >> >> I came across pahole <http://linux.die.net/man/1/pahole>, and it's >> able to show some pretty interesting info about ATS internal >> structures. It looks like there's probably some opportunities to >> pack structure better, and probably improve cache utilization. >> >> For example, HttpSM could be 54 bytes smaller: > > Awesome! And, as always, I'm here to ask the uncomfortable questions > so no one else has to: > > How is that going to fare with ABI compatibility? > How does this compare between 32bit and 64bit? > How does it compare between different platforms? This all depends on the changes we make (if any). pahole is showing you the actual structure layout by examining the debug information. There's only a couple of places where we expose structs to plugins, so I don't believe that there's much ABI at risk. As for different platforms, you would need to build on the platform that you care about examine the debug infor on that platform. I expect that the layout would not be significantly different. It would be interesting to dump some memory stats from a busy site and figure out which structures are hot. > >> ~/trafficserver.git$ pahole -C HttpSM ./proxy/.libs/traffic_server >> die__process_function: tag not supported (template_type_parameter)! >> die__process_class: tag not supported (template_value_parameter)! >> struct HttpSM : public Continuation { >> struct History { >> const char * fileline; /* 0 8 >> */ >> short unsigned int event; /* 8 2 >> */ >> short int reentrancy; /* 10 2 >> */ >> >> /* size: 16, cachelines: 1, members: 3 */ >> /* last cacheline: 16 bytes */ >> >> /* BRAIN FART ALERT! 16 != 12 + 0(holes), diff = 4 */ >> >> }; >> >> class Link_debug_link : public Link<HttpSM> { >> public: >> >> /* struct Link<HttpSM> <ancestor>; */ /* 0 16 >> */ >> class HttpSM * & next_link(class HttpSM *); /* >> linkage=_ZN6HttpSM15Link_debug_link9next_linkEPS_ */ >> >> class HttpSM * & prev_link(class HttpSM *); /* >> linkage=_ZN6HttpSM15Link_debug_link9prev_linkEPS_ */ >> >> const class HttpSM * next_link(const class HttpSM *); /* >> linkage=_ZN6HttpSM15Link_debug_link9next_linkEPKS_ */ >> >> const class HttpSM * prev_link(const class HttpSM *); /* >> linkage=_ZN6HttpSM15Link_debug_link9prev_linkEPKS_ */ >> >> >> /* size: 16, cachelines: 1, members: 1 */ >> /* last cacheline: 16 bytes */ >> }; >> >> public: >> >> /* struct Continuation <ancestor>; */ /* 0 48 */ >> int64_t sm_id; /* 48 8 */ >> unsigned int magic; /* 56 4 */ >> bool enable_redirection; /* 60 1 */ >> bool api_enable_redirection; /* 61 1 */ >> >> /* XXX 2 bytes hole, try to pack */ >> >> /* --- cacheline 1 boundary (64 bytes) --- */ >> char * redirect_url; /* 64 8 */ >> int redirect_url_len; /* 72 4 */ >> int redirection_tries; /* 76 4 */ >> int64_t transfered_bytes; /* 80 8 */ >> bool post_failed; /* 88 1 */ >> bool debug_on; /* 89 1 */ >> >> /* XXX 2 bytes hole, try to pack */ >> >> enum HttpPluginTunnel_t plugin_tunnel_type; /* 92 4 */ >> class PluginVCCore * plugin_tunnel; /* 96 8 */ >> struct State t_state; /* 104 5920 */ >> protected: >> >> /* --- cacheline 94 boundary (6016 bytes) was 8 bytes ago --- */ >> int reentrancy_count; /* 6024 4 */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> struct History history[64]; /* 6032 1024 */ >> /* --- cacheline 110 boundary (7040 bytes) was 16 bytes ago --- */ >> int history_pos; /* 7056 4 */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> class HttpTunnel tunnel; /* 7064 1072 */ >> /* --- cacheline 127 boundary (8128 bytes) was 8 bytes ago --- */ >> struct HttpVCTable vc_table; /* 8136 288 */ >> /* --- cacheline 131 boundary (8384 bytes) was 40 bytes ago --- */ >> class HttpVCTableEntry * ua_entry; /* 8424 8 */ >> class HttpClientSession * ua_session; /* 8432 8 */ >> enum BackgroundFill_t background_fill; /* 8440 4 */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> /* --- cacheline 132 boundary (8448 bytes) --- */ >> class IOBufferReader * ua_buffer_reader; /* 8448 8 */ >> class HttpVCTableEntry * server_entry; /* 8456 8 */ >> class HttpServerSession * server_session; /* 8464 8 */ >> int shared_session_retries; /* 8472 4 */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> class IOBufferReader * server_buffer_reader; /* 8480 8 */ >> struct HttpTransformInfo transform_info; /* 8488 16 */ >> struct HttpTransformInfo post_transform_info; /* 8504 16 */ >> /* --- cacheline 133 boundary (8512 bytes) was 8 bytes ago --- */ >> class HttpCacheSM cache_sm; /* 8520 184 */ >> /* --- cacheline 136 boundary (8704 bytes) --- */ >> class HttpCacheSM transform_cache_sm; /* 8704 184 */ >> /* --- cacheline 138 boundary (8832 bytes) was 56 bytes ago --- */ >> class HttpCacheSM * second_cache_sm; /* 8888 8 */ >> /* --- cacheline 139 boundary (8896 bytes) --- */ >> HttpSMHandler default_handler; /* 8896 16 */ >> class Action * pending_action; /* 8912 8 */ >> class Action * historical_action; /* 8920 8 */ >> class Continuation * schedule_cont; /* 8928 8 */ >> struct HTTPParser http_parser; /* 8936 48 */ >> /* --- cacheline 140 boundary (8960 bytes) was 24 bytes ago --- */ >> enum StateMachineAction_t last_action; /* 8984 4 */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> struct { >> int (*__pfn)(class HttpSM *, int, void *); /* >> 8992 >> 8 */ >> long int __delta; /* 9000 8 */ >> } m_last_state; /* 8992 16 */ >> int client_request_hdr_bytes; /* 9008 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t client_request_body_bytes; /* 9016 8 >> */ >> /* --- cacheline 141 boundary (9024 bytes) --- */ >> int server_request_hdr_bytes; /* 9024 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t server_request_body_bytes; /* 9032 8 >> */ >> int server_response_hdr_bytes; /* 9040 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t server_response_body_bytes; /* 9048 >> 8 */ >> int client_response_hdr_bytes; /* 9056 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t client_response_body_bytes; /* 9064 >> 8 */ >> int cache_response_hdr_bytes; /* 9072 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t cache_response_body_bytes; /* 9080 8 >> */ >> /* --- cacheline 142 boundary (9088 bytes) --- */ >> int pushed_response_hdr_bytes; /* 9088 4 >> */ >> >> /* XXX 4 bytes hole, try to pack */ >> >> int64_t pushed_response_body_bytes; /* 9096 >> 8 */ >> class TransactionMilestones milestones; /* 9104 152 */ >> /* --- cacheline 144 boundary (9216 bytes) was 40 bytes ago --- */ >> int hooks_set; /* 9256 4 */ >> TSHttpHookID cur_hook_id; /* 9260 4 */ >> class APIHook * cur_hook; /* 9264 8 */ >> int64_t prev_hook_start_time; /* 9272 8 */ >> /* --- cacheline 145 boundary (9280 bytes) --- */ >> int cur_hooks; /* 9280 4 */ >> enum HttpApiState_t callout_state; /* 9284 4 */ >> class HttpAPIHooks api_hooks; /* 9288 264 */ >> /* --- cacheline 149 boundary (9536 bytes) was 16 bytes ago --- */ >> bool terminate_sm; /* 9552 1 */ >> bool kill_this_async_done; /* 9553 1 */ >> >> /* XXX 6 bytes hole, try to pack */ >> >> struct Link<HttpSM> debug_link; /* 9560 16 */ >> ... >> >> /* vtable has 4 entries: { >> [2] = destroy(_ZN6HttpSM7destroyEv), >> [3] = handle_api_return(_ZN6HttpSM17handle_api_returnEv), >> [4] = set_next_state(_ZN6HttpSM14set_next_stateEv), >> [5] = kill_this_async_hook(_ZN6HttpSM20kill_this_async_hookEiPv), >> } */ >> /* size: 9576, cachelines: 150, members: 62 */ >> /* sum members: 9522, holes: 14, sum holes: 54 */ >> /* last cacheline: 40 bytes */ >> }; >> >> > > -- > Igor Galić > > Tel: +43 (0) 664 886 22 883 > Mail: i.ga...@brainsware.org > URL: http://brainsware.org/ > GPG: 6880 4155 74BD FD7C B515 2EA5 4B1D 9E08 A097 C9AE >
