MINOR: tasks/activity: improve the caller-callee activity hash

The previous dump already showed that the "other" category was getting
a few entries. Let's proceed like for the memory profiling, by scanning
a limited range of adjacent slots to find a spare one (16 max). That's
pretty fast since close and likely prefetched and the comparison is
cheap. The new dump now shows up to 45 entries below without "other":

Now:
Tasks activity:
  function                      calls   cpu_tot   cpu_avg   lat_tot   lat_avg
  task_run_applet                  22   34.56ms   1.571ms   1.145ms   52.04us <- sc_applet_create@src/stconn.c:489 appctx_wakeup
  task_run_applet                  21   11.11us   529.0ns   2.590ms   123.3us <- run_tasks_from_lists@src/task.c:652 task_drop_running
  task_run_applet                   5   7.715ms   1.543ms   2.186us   437.0ns <- sc_app_chk_snd_applet@src/stconn.c:996 appctx_wakeup
  accept_queue_process            345   3.129ms   9.068us   72.84ms   211.1us <- listener_accept@src/listener.c:1099 tasklet_wakeup
  accept_queue_process             32   113.0us   3.529us   3.070ms   95.94us <- accept_queue_process@src/listener.c:165 tasklet_wakeup
  sc_conn_io_cb               5026032   3.037s    604.0ns   17.47m    208.5us <- sc_app_chk_rcv_conn@src/stconn.c:762 tasklet_wakeup
  sc_conn_io_cb               4361192   7.626s    1.748us   3.179m    43.74us <- h1_wake_stream_for_recv@src/mux_h1.c:2600 tasklet_wakeup
  sc_conn_io_cb                178293   275.4ms   1.544us   2.740m    922.0us <- qcs_notify_send@src/mux_quic.c:529 tasklet_wakeup
  sc_conn_io_cb                  2561   15.84ms   6.185us   1.036s    404.4us <- h1_wake_stream_for_send@src/mux_h1.c:2610 tasklet_wakeup
  sc_conn_io_cb                   453   261.4us   577.0ns   86.79ms   191.6us <- h2s_notify_recv@src/mux_h2.c:1298 tasklet_wakeup
  sc_conn_io_cb                    89   50.05us   562.0ns   100.7ms   1.131ms <- qcs_notify_recv@src/mux_quic.c:519 tasklet_wakeup
  sc_conn_io_cb                     8   19.04us   2.379us   472.5us   59.06us <- sock_conn_iocb@src/sock.c:869 tasklet_wakeup
  process_resolvers                50   57.50us   1.149us   1.116ms   22.32us <- wake_expired_tasks@src/task.c:429 task_drop_running
  srv_cleanup_idle_conns            8   5.669us   708.0ns   216.6us   27.08us <- wake_expired_tasks@src/task.c:429 task_drop_running
  process_stream              4599847   48.79s    10.61us   16.92m    220.7us <- sc_notify@src/stconn.c:1209 task_wakeup
  process_stream              4530081   52.82s    11.66us   14.92m    197.6us <- stream_new@src/stream.c:563 task_wakeup
  process_stream                   15   201.7us   13.45us   31.58ms   2.105ms <- sc_app_chk_snd_conn@src/stconn.c:857 task_wakeup
  h1_io_cb                    7861205   18.22s    2.317us   2.408m    18.38us <- sock_conn_iocb@src/sock.c:869 tasklet_wakeup
  h1_io_cb                     474763   1.379s    2.905us   6.578m    831.4us <- conn_subscribe@src/connection.c:732 tasklet_wakeup
  h1_io_cb                      34830   38.64ms   1.109us   18.85s    541.2us <- h1_takeover@src/mux_h1.c:4085 tasklet_wakeup
  h1_io_cb                       2561   2.150ms   839.0ns   674.4ms   263.3us <- sock_conn_iocb@src/sock.c:849 tasklet_wakeup
  h1_timeout_task                2634   588.5us   223.0ns   890.5ms   338.1us <- h1_release@src/mux_h1.c:1087 task_wakeup
  h2_timeout_task                  16   7.519us   469.0ns   1.146ms   71.63us <- h2_release@src/mux_h2.c:1191 task_wakeup
  h2_io_cb                      99601   2.212s    22.21us   19.33s    194.1us <- h2_snd_buf@src/mux_h2.c:6712 tasklet_wakeup
  h2_io_cb                      79777   146.6ms   1.837us   3.529s    44.24us <- h2c_restart_reading@src/mux_h2.c:856 tasklet_wakeup
  h2_io_cb                      60698   2.259s    37.21us   4.704s    77.50us <- sock_conn_iocb@src/sock.c:869 tasklet_wakeup
  h2_io_cb                          5   36.90us   7.380us   2.045ms   409.0us <- h2_do_shutw@src/mux_h2.c:4656 tasklet_wakeup
  qc_io_cb                      26595   8.007s    301.1us   4.261s    160.2us <- qc_treat_acked_tx_frm@src/xprt_quic.c:1695 tasklet_wakeup
  qc_io_cb                       7921   5.284s    667.1us   2.171s    274.1us <- qc_stream_desc_ack@src/quic_stream.c:128 tasklet_wakeup
  qc_io_cb                       6229   5.851s    939.3us   1.856s    297.9us <- h3_snd_buf@src/h3.c:1084 tasklet_wakeup
  qc_io_cb                        994   699.1ms   703.3us   174.9ms   176.0us <- qcc_release_remote_stream@src/mux_quic.c:1200 tasklet_wakeup
  qc_io_cb                         65   9.883ms   152.0us   13.33ms   205.1us <- qc_process_timer@src/xprt_quic.c:4602 tasklet_wakeup
  qc_io_cb                          1   293.5us   293.5us   105.9us   105.9us <- qcs_consume@src/mux_quic.c:800 tasklet_wakeup
  qc_io_cb                          1   10.87us   10.87us   3.307us   3.307us <- qc_init@src/mux_quic.c:2057 tasklet_wakeup
  quic_conn_io_cb                   2   2.531ms   1.265ms   2.839us   1.419us <- qc_lstnr_pkt_rcv@src/xprt_quic.c:6184 tasklet_wakeup_after
  quic_conn_app_io_cb           61392   2.620s    42.67us   268.0ms   4.365us <- qc_lstnr_pkt_rcv@src/xprt_quic.c:6184 tasklet_wakeup_after
  quic_conn_app_io_cb             408   10.56ms   25.88us   124.0ms   303.8us <- qc_process_timer@src/xprt_quic.c:4635 tasklet_wakeup
  quic_conn_app_io_cb               2   15.61us   7.806us   103.2us   51.59us <- qc_process_timer@src/xprt_quic.c:4589 tasklet_wakeup
  quic_conn_app_io_cb               1   410.6us   410.6us   11.52us   11.52us <- qc_xprt_start@src/xprt_quic.c:7122 tasklet_wakeup
  quic_lstnr_dghdlr             62716   409.2ms   6.523us   21.81s    347.8us <- quic_lstnr_dgram_dispatch@src/quic_sock.c:255 tasklet_wakeup
  qc_process_timer                410   245.4us   598.0ns   238.5ms   581.7us <- wake_expired_tasks@src/task.c:344 task_wakeup
  quic_accept_run                   1   7.711us   7.711us   82.28us   82.28us <- quic_accept_push_qc@src/quic_sock.c:458 tasklet_wakeup
1 file changed