What're you trying to accomplish?
Can you include the output of "stats" and "stats settings" on both
machines?
Dumb question but you've looked at the output of `ps auxH`? If just using
htop you may not see the threads that're idle.
TCP connections are pinned to a specific worker thread on connection.
Trivial benchmarks may not load the worker threads evenly, as the
connections are handed to threads evenly via round robin.
On Sun, 15 Dec 2019, Alireza Sanaee wrote:
> Hi,
> Thank you for the information,
>
> Sorry for miss using the word there, yes that's all threads. I'm using the
> Memcached 1.5.20. I build it myself and then run my experiments($MEMCACHED -u
> root -p 11211 -m $MAXMEM -c 1024 -t $MEMCACHED_THREADS). And I'm checking the
> number of Memcached threads in htop output. It showed me 10 threads(workers
> included) in one machine and 6 threads(workers included) on the other one.
>
> To share some more information, I have 200GB of memory for the bigger machine
> that creates only 6 threads, and we have only 16GB of memory for the machine
> that creates 10 threads. I'm just thinking maybe because the smaller machine
> has less amount of space, and I'm actually filling in up to 15GB then I might
> have more work to do and creates more threads.
>
> According to your information, I should expect at least 5 threads other than
> the main workers. So 10 threads look OK, but how about the bigger machine
> which spawns only 6 threads?
>
> I also had difficulties in detecting the worker threads that respond to
> GET/SET requests on my results, I have attached two pictures, one of them
> shows
> the actual location of each worker on various cores, and the second one is
> showing userspace time spent for each worker. Apparently worker thread number
> 1,2,4 and 5 have spent more time in userspace, so I'm concluding here that
> 1,2,4 and 5 are my actual worker threads, and worker 3 and 6 are just internal
> worker threads of Memcached. Does that make sense to you?
>
> Thanks,
> Alireza
>
>
> On Sun, Dec 15, 2019 at 7:19 AM dormando wrote:
> What version of memcached is on each machine?
>
> memcached doesn't use processes, it's multi-threaded. Different versions
> may have a different number of background threads. In the latest version
> there should be at least:
>
> - listener thread (main "process")
> - N worker threads
> - hash table maintenance thread
> - async log thread (for `watch` commands)
> - LRU maintainer thread
> - LRU crawler thread
> - slab rebalancer thread
>
> they're all idle unless they need to do work. LRU maintenance thread is
> probably the most active, since it executes LRU maintenance work
> deferred
> from the worker threads. Older versions have some of these threads, but
> they were not enabled by default until 1.5.0.
>
> -Dormando
>
> On Sat, 14 Dec 2019, Alireza Sanaee wrote:
>
> > Hello,
> > I'm running Memcached on two different machines with different
> specifications. And I specify the number of worker threads = 4 for both
> machines. However,
> > the number of child processes of the Memcached server is different on
> two machines. On one of them, I have 6 Memcached child processes, and
> on the other
> > server, I have 10 Memcached child processes. I'm curious to
> understand how many children processes Memcached is basically spawning other
> than the worker
> > threads, and for what tasks?
> >
> > I expect the Memcached to spawn only 4 children processes or a
> certain number of children processes on two machines, however, it seems not
> true.
> >
> > Thanks,
> > Alireza
> >
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