Date: Mon, 18 Jun 2018 09:08:14 -0700 From: Kevin Oberman <rkoberman@gmail.com> To: tech-lists <tech-lists@zyxst.net> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, Mailinglists FreeBSD <freebsd-questions@freebsd.org> Subject: Re: lightly loaded system eats swap space Message-ID: <CAN6yY1uvdj7HY4VJwygDqRE%2BCUuVwBbbkunH8aU4vRqvRhkbgQ@mail.gmail.com> In-Reply-To: <ab5d0cb0-13f5-5de8-6189-c0a5c621c6e9@zyxst.net> References: <c8277497-ffcf-0503-490b-96d1b4605af7@zyxst.net> <20180618160855.44d9a0c2.freebsd.ed.lists@sumeritec.com> <ab5d0cb0-13f5-5de8-6189-c0a5c621c6e9@zyxst.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, Jun 18, 2018 at 5:27 AM, tech-lists <tech-lists@zyxst.net> wrote: > On 18/06/2018 09:08, Erich Dollansky wrote: > >> Hi, >> >> On Sun, 17 Jun 2018 23:19:02 +0100 >> tech-lists <tech-lists@zyxst.net> wrote: >> >> freebsd-11-stable r333874, ZFS raidz1-0 (3x4TB disks), 128GB RAM, >>> Swap: 4096M Total, 3502M Used, 594M Free, 85% Inuse >>> >> >> this might not be related but I noticed that your swap space is small >> compared to RAM size. I noticed on a much smaller Raspberry Pi, that it >> runs into trouble when there is no swap even there is enough RAM >> available. Is it easily possible for you to add some GB of swap space >> and let the machine run then? >> >> How much swap do the other machines have? >> > > Hi, > > Yes, the machine with the problem uses the default 4GB swap. That's all > the swap it has. The machine without issue has a swapfile installed on a > SSD in addition to the default 4GB swap. > > problematic machine: > Device 512-blocks Used Avail Capacity > /dev/ada0p3 8388608 3.3G 714M 83% > > machine without a problem, it has swapfile installed: > Device 512-blocks Used Avail Capacity > /dev/ada0s1b 8262248 1.7G 2.2G 44% > /dev/md0 65536000 1.9G 29G 6% > Total 73798248 3.7G 32G 10% > > I added the swapfile a long time ago on this machine due to the same issue. > > But my problem isn't so much an out of swapspace problem; all this is, is > a symptom. My problem is "why is it swapping out at all on a 128GB system > and why is what's swapped out not being swapped back in again". > > thanks, > -- > J. Small correction. Your problem is "why is it swapping out at all on a 128GB system ." Once pages are swapped out, they are never swapped back in until/unless they are needed. There is no reason to waste time/disk activity to swap pages back into memory unless they are required. RAM is always more valuable than swap. Ir is easy to write a process that eats up a large amount of memory, then goes idle without freeing it. The memory will get pages out, fill swap, and, unless the process terminates or becomes active, will consume up a great deal of swap space "forever". Firefox is a good example of this. I have to restart it every day or two and occasionally will run out of swap which results in a nearly deadlocked system. It can take many minutes to just kill firefox. -- Kevin Oberman, Part time kid herder and retired Network Engineer E-mail: rkoberman@gmail.com PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAN6yY1uvdj7HY4VJwygDqRE%2BCUuVwBbbkunH8aU4vRqvRhkbgQ>