Date: Wed, 28 Feb 2018 10:55:17 -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: <20180228185517.GB26187@www.zefox.net> In-Reply-To: <a759ecea-83f4-b0b2-7113-c39633f68637@mgm51.com> References: <20180228170311.GA26187@www.zefox.net> <a759ecea-83f4-b0b2-7113-c39633f68637@mgm51.com>
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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 reading, bob prohaska
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