Date: Tue, 29 Dec 2020 08:42:01 +0100 From: Michael Schuster <michaelsprivate@gmail.com> To: Pete Wright <pete@nomadlogic.org> Cc: doug@safeport.com, freeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Observations on virtual memory operations Message-ID: <CADqw_gKWdMaMpCq=%2By=_pvd6wp2bJvDsWkv5GYTwrznhCSpfeQ@mail.gmail.com> In-Reply-To: <8f3a278a-56cd-c732-68a0-cf6fa5d50a3f@nomadlogic.org> References: <167603f-a82a-7031-6850-2d08f17a36@fledge.watson.org> <8f3a278a-56cd-c732-68a0-cf6fa5d50a3f@nomadlogic.org>
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On Tue, Dec 29, 2020, 00:37 Pete Wright <pete@nomadlogic.org> wrote: > > > On 12/28/20 3:25 PM, doug wrote: > > I have two servers running jails that "routinely" run out of swapspace > > with > > no demand paging activity. To try and get a handle on VM/swapspace > > management I have been tracking swapinfo vs memory use as measured by > > top. > > The numbers do not exactly add up but I assume that is not involved in my > > issue. > > > <snip> > > > > The other day I caught the system at 73% swapspace used. At this level > > the > > system was in a near thrashing state in that typing a key got it > > echoed in > > 10 <--> 30 seconds. There was about 600MB of swapspace at this point. I > > would think there is no way to debug this except as a thought experiment. > > The first thing that comes to mind is do you have the ability to hook > any metrics/monitoring onto this system. For example, I use collectd on > my systems to report overall CPU/memory metrics as well as per-process > memory metrics. > > Alternatively you could write a simple shell script that run's "ps" and > parses the output of memory utilization on a per-process basis. > > either of the above approaches should give you some insight into where > the memory leak is coming from (assuming you already do not know). > > one trick i use is to invoke a process with "limits" to ensure it does > not exceed a certain amount of memory that I allocate to it. for example > with firefox i do this: > $ limits -m 6g -v 6g /usr/local/bin/firefox > > that should at least buy you enough time to investigate why the process > needs so much memory and see what you can do about it. > If the usual observation tools (and please note, I don't have too much specific knowledge here) don't tell you what you need to know, have a look at DTrace. Again, I have no (active) specific knowledge; personally, I would start with Brendan Gregg's tools (ask your favourite search engine)... Regards Michael
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