Date: Wed, 28 Feb 2018 13:43:01 -0800 From: bob prohaska <fbsd@www.zefox.net> To: Mike <the.lists@mgm51.com> Cc: freebsd-arm@freebsd.org, bob prohaska <fbsd@www.zefox.net> Subject: Re: Is maximum swap usage tunable? Message-ID: <20180228214301.GA29481@www.zefox.net> In-Reply-To: <8f422161-885e-aa91-eacd-018540222d65@mgm51.com> References: <20180228170311.GA26187@www.zefox.net> <a759ecea-83f4-b0b2-7113-c39633f68637@mgm51.com> <20180228185517.GB26187@www.zefox.net> <8f422161-885e-aa91-eacd-018540222d65@mgm51.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Feb 28, 2018 at 02:37:36PM -0500, Mike wrote: > On 2/28/2018 1:55 PM, bob prohaska wrote: > > On Wed, Feb 28, 2018 at 12:20:56PM -0500, Mike wrote: > >> On 2/28/2018 12:03 PM, bob prohaska wrote: > >>> In watching system compilations on an RPi3 it looks as if the > >>> system starts killing processes with "out of swap" warnings > >>> well below 50% of full utilization (in this case, 2 GB). One > >>> recent instance of make -j4 kernel-toolchain killed llvm-tblgen > >>> with only 34% of the swap in use. > >>> > >>> Is the maximum swap usage limit adjustable in any way? I didn't > >>> recognize anything useful in the page at > >>> https://www.freebsd.org/cgi/man.cgi?query=sysctl(8)&sektion=&manpath=freebsd-release-ports > >>> > >>> It's possible the problem is really swap speed, rather than size, so I'd > >>> like to try changing size limits if possible. The swap media claims 2-3 > >>> MB/sec random write speed and observations with gstat seem to support the > >>> claim, but transient stalls are hard to observe. An RPi2 with similar > >>> hardware seems to have no problems. > >>> > >> > >> > >>> It's possible the problem is really swap speed > >> > >> I was running into swap speed / timeout issues. There were messages on > >> the console to that effect. > >> > >> Once I put the swap space on rotating rust, that part of the compile > >> problem disappeared. I use 1GB swap space. > >> > > > > The latest kernel versions seem to have largely done away with the > > "indefinite wait buffobj" warnings. They're few and far between, > > the compile proceeds unless they're abundant. The fact that armv7 > > has no problem, and the system is reporting "out of swap" with 34% > > in use strikes me as suspicious. Kernel and userland are in sync, > > so the figure of 34% swap usage is probably accurate. > > > > Perhaps my question is better phrased thus: How does FreeBSD-arm > > determine when it's out of swap? > > > > > Thanks for the follow-up. > > I was planning to download and try the > > RPI3-20180226-r330034 > > image file this evening. Per your comment, I'll not use the rusty swap > space, and see what happens. > > I'll report back, probably on the morrow... > FWIW, I've been using Sandisk Extreme USB 3 flash drives for /usr /var/ and swap on the Pi3. It seems that flash write speed is a tighter bottleneck than USB 2.0 ports on the Pi. Attempts to use older, slower USB 2 flash drives on a Pi2 didn't work, though the symptoms were never "out of swap". Good luck! bob prohaska
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20180228214301.GA29481>