----- 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?
> ~/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
