Hi Guys,
We' ve been using ATS as a reverse proxy, and a few week ago We started to
use the interim cache feature in more intense way, caching objects with the
average size of 200 MB and max size of 1 GB.
*We have ~ 1 TB HDD as a default storage:*
cat /etc/trafficserver/storage.config
# ATS - Storage
/dev/sda6 volume=1
*And also, a 120 GB SDD storage as interim cache:*
LOCAL proxy.config.cache.interim.storage STRING /dev/sdc1
After 20 ~ 30 minutes in production with this configuration, We could
notice a sudden CPU high usage, increasing up to 65 %, considering that our
regular usage is 10 %. However the throughput still stable in 250 Mbps per
box.
We've found the following behavior using the perf top tool:
88.18% traffic_server [.]
_Z15write_to_net_ioP10NetHandlerP18UnixNetVConnectionP7EThread
0.32% traffic_server [.] _ZN10NetHandler12mainNetEventEiP5Event
0.30% [kernel] [k] update_sd_lb_stats
0.29% [e1000e] [k] e1000e_check_ltr_demote
0.25% [kernel] [k] __ticket_spin_lock
0.24% traffic_server [.] _ZN7EThread13process_eventEP5Eventi
0.21% [kernel] [k] timerqueue_add
0.17% libc-2.12.so [.] epoll_wait
0.17% libpcre.so.0.0. [.] 0x00000000000100dd
0.14% [kernel] [k] __schedule
1) This behavior is easily reproduced caching* large objects with interim
cache active*.
2) With interim cache *disabled*, this behavior* is not reproduced.*
As you can see, at the perf top output, the write_to_net_*io *function is
responsible for this heavy CPU usage. We would like to hear of you guys, if
anyone has faced a issue like that, or if you have any clues about this
possible bug.
Thanks & Regards,
--
Daniel Biazus
infrastructure Engineering
Azion Technologies
Porto Alegre, Brasil +55 51 3012 3005 | +55 51 82279032
Miami, USA +1 305 704 8816
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