Re: radosgw pegging down 5 CPU cores when no data is being transferred

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Hi Vladimir,


On 8/21/19 8:54 AM, Vladimir Brik wrote:
Hello

I am running a Ceph 14.2.1 cluster with 3 rados gateways. Periodically, radosgw process on those machines starts consuming 100% of 5 CPU cores for days at a time, even though the machine is not being used for data transfers (nothing in radosgw logs, couple of KB/s of network).

This situation can affect any number of our rados gateways, lasts from few hours to few days and stops if radosgw process is restarted or on its own.

Does anybody have an idea what might be going on or how to debug it? I don't see anything obvious in the logs. Perf top is saying that CPU is consumed by radosgw shared object in symbol get_obj_data::flush, which, if I interpret things correctly, is called from a symbol with a long name that contains the substring "boost9intrusive9list_impl"


I don't normally look at the RGW code so maybe Matt/Casey/Eric can chime in.  That code is in src/rgw/rgw_rados.cc in the get_obj_data struct.  The flush method does some sorting/merging and then walks through a listed of completed IOs and appears to copy a bufferlist out of each one, then deletes it from the list and passes the BL off to client_cb->handle_data.  Looks like it could be pretty CPU intensive but if you are seeing that much CPU for that long it sounds like something is rather off.


You might want to try grabbing a a callgraph from perf instead of just running perf top or using my wallclock profiler to see if you can drill down and find out where in that method it's spending the most time.


My wallclock profiler is here:


https://github.com/markhpc/gdbpmp


Mark



This is our configuration:
rgw_frontends = civetweb num_threads=5000 port=443s ssl_certificate=/etc/ceph/rgw.crt error_log_file=/var/log/ceph/civetweb.error.log

(error log file doesn't exist)


Thanks,

Vlad
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