Re: [Proftpd-user] RLimitMemory question
Bob Friesenhahn <[email protected]>
| Newsgroups | gmane.network.proftpd.user |
|---|---|
| Message-ID | <[email protected]> |
On Mon, 13 Aug 2018, Ian via Proftp-user wrote: > > Immediate after logging in, i looked at htop and it showed that the authenticated proftpd process is using up 196MB of Virtual memory . if each session takes up 196MB of VM inside an 8GB RAM server, at most we can support is 47 concurrent sessions? > > What's a strategy to scale up without adding a lot of hardware? use a large swap space ? Virtual memory is "virtual" (just a number!) and thus it does not necessarily consume any RAM. It may be that the RLimitMemory feature is not very effective since it is based on virtual memory (address space) rather than the actual memory used. Much of the virtual memory is shared with other processes (e.g. all the shared library and executable read-only text and writeable initialized data "BSS" which has not been modified) and so adding more processes does not substantially increase the actual amount of RAM used. In a forking server, the child process which provides the service shares unmodified memory pages with its parent process (e.g. Proftpd) and depending on server implementation, the child might not use much more RAM. Virtual memory is typically allocated in 4k blocks and the child needs some blocks for its own stack and might burn a 4k block for each shared library used. If this is a Linux system, then you can examine /proc/[pid]/smaps to see where the memory in the child process is attributed to and if it is private or shared with other processes. Read-only shared data does not multiply with added sessions. Bob -- Bob Friesenhahn [email protected], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ ProFTPD Users List <[email protected]> Unsubscribe problems? http://www.proftpd.org/list-unsub.html