[chrony-dev] Proposal for improvement of memory consumption in chronyd.

[timekeeper@xxxxxxxxx]

Dear Chrony community,

We recently start with chrony.eu public ntp pool. As number of clients 
increases we observe in our monitoring platform that aged out clients do 
not free memory. We run chrony servers in "xleave" mode with 
"clientloglimit" of 512 MB and current peak memory consumption for 
particular graph set is 148 MB (img2.gif). I attached three graphs with 
number of clients in last six hours. As 2^^14 seconds (cca. 4.5 hrs ) is 
maximum pooling time of client I expected that aged out clients would be 
removed from memory, that client data has no practical value. In 
particular example (img1.gif all numbers in thousands):
- left graph shows number of active clients 137,73k : 41%,
- middle graph shows number of timed out clients 198,70k : 59%,
- right graph shows number of all clients 336,35k : 100%.

Out of all clients 59% of clients data is outdated. We can very easily 
reach more than 1-2 million clients, with similar ratio betwen number of 
outdated and all clients. All this data is for single server only. We 
have four servers with similar situation, but currentlly only one server 
in pool.

Is it possible to introduce set of configuration parameter(s) which 
would address this issue and hadle succh situations ?

   Best regards

        Boris Gabrič / timekeeper

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timekeeper@xxxxxxxxx
https://www.chrony.eu

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