Date: Sun, 7 Sep 2025 07:13:10 +0100 From: Graham Perrin <grahamperrin@gmail.com> To: freebsd-pkg@freebsd.org Cc: freebsd-pkgbase@freebsd.org Subject: Re: pkg upgrade, ZFS, swap on, vm.pageout_oom_seq Message-ID: <e83f7cb6-a635-4ffe-a794-b990c627fafe@gmail.com> In-Reply-To: <05351AB0-7BA7-4130-BBEE-CFB793ACFAB4@yahoo.com> References: <D2C64F39-B6EA-47BD-B88E-B4D729BE0150@yahoo.com> <0dbf8c95-7697-4887-a890-335c3ccd80f1@gmail.com> <4e12afdc-7bcf-4a25-94b3-fe1562469ed9@gmail.com> <05351AB0-7BA7-4130-BBEE-CFB793ACFAB4@yahoo.com>
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On 07/09/2025 05:11, Mark Millard wrote: > On Sep 6, 2025, at 19:10, Graham Perrin <grahamperrin@gmail.com> wrote: > >> … > … > > So you are saying at this point that the combination for > RAM+SWAP inside the VM is: > > 1 GiByte RAM in VM and 8 GiByte SWAP in that VM as well? Yes. > If yes, that should have produced a warning about potential > mistuning … True. I spent years ignoring the kern.maxswzone warning, partly because I never noticed any adverse effect from ignorance. When set to 16 G on hardware with 32 G RAM, the amount of swap used was sometimes close to the amount available. Today I found the variable in loader_simp(8) under <https://man.freebsd.org/cgi/man.cgi?query=loader_simp&sektion=8&manpath=freebsd-current#BUILTIN%09COMMANDS>, > … If no value is provided, the system allocates enough memory to > handle an amount of swap that corresponds to eight times the amount of > physical memory present in the system. > > Note that swap metadata can be fragmented, which means that the system > can run out of space before it reaches the theoretical limit. > Therefore, care should be taken to not configure more swap than > approximately half of the theoretical maximum. > > Running out of space for swap metadata can leave the system in an > unrecoverable state. Therefore, you should only change this parameter > if you need to greatly extend the KVM reservation for other resources > such as … Without me attempting to perform any calculation: I reckon, I always did well (no unexpected run-out) by _not_ providing a value.home | help
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