Date: Wed, 24 Feb 2021 10:08:37 -0800 From: Mark Millard <marklmi@yahoo.com> To: Alan Somers <asomers@freebsd.org> Cc: Olivier Certner <olivier.freebsd@free.fr>, Konstantin Belousov <kostikbel@gmail.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: The out-of-swap killer makes poor choices Message-ID: <96B17A3F-4663-42E2-9D29-C022803C9864@yahoo.com> In-Reply-To: <CAOtMX2iYr4NDYE0xHSa_w1hA5XQ2m9cA28NzPoGbfzAKKox9aQ@mail.gmail.com> References: <CAOtMX2jYmrK7ftx62_NEfNCWS7O=giHKL1p9kXCqq1t5E1arxA@mail.gmail.com> <CAOtMX2i3Njo=KBP=99_G0%2BKuSa00CVgNvacmzhTaoZUYEhwPPA@mail.gmail.com> <YDYyQ1V/hEAGV%2ByJ@kib.kiev.ua> <1984125.0OzZcVfBr4@ravel> <CAOtMX2iYr4NDYE0xHSa_w1hA5XQ2m9cA28NzPoGbfzAKKox9aQ@mail.gmail.com>
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On 2021-Feb-24, at 09:34, Alan Somers <asomers at freebsd.org> wrote: >> . . . >=20 > There's another silly problem that I didn't mention in my original = post. > The old rule of thumb is that the swap partition's size should be = twice as > large as the amount of RAM. However, that's no longer possible in = many > cases. The kernel imposes a hard limit of 64 GiB (on amd64 at least) = on > the usable size of any swap partition, and many servers now have far = more > than 64 GiB of RAM. So the advice needs to change with the times. I = don't > know what the best size would be for a modern server, but I would = guess > that it must be at least several times the RSS of your largest = process, and > also at least one tenth of RAM (for use as a dump device with = compressed > core dumps). That was fixed in main at least: # swapinfo Device 1K-blocks Used Avail Capacity /dev/gpt/FBSDFHUGEswap 201326592 0 201326592 0% That is from a system based on main 3acea07c1873 : # ~/fbsd-based-on-what-freebsd-main.sh=20 merge-base: 3acea07c1873b1e4042f4a4fa8668745ee59f15b merge-base: CommitDate: 2021-02-08 19:15:21 +0000 c1845d00f818 (HEAD -> mm-src) mm-src snapshot for mm's patched build in = git context. 3acea07c1873 (pure-src) Restore the augmented strlen commentary FreeBSD FBSDFHUGE 14.0-CURRENT FreeBSD 14.0-CURRENT = mm-src-n244686-c1845d00f818 GENERIC-NODBG amd64 amd64 1400004 1400004 But the change is older than that. There was a period where I had three 64 GiByte swap partitions instead of one 192 GiByte swap partition, because each was forcibly limited in size but the total was not (on the scale involved in the example context). =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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