Date: Wed, 24 Feb 2021 20:36:07 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Alan Somers <asomers@freebsd.org> Cc: Olivier Certner <olivier.freebsd@free.fr>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: The out-of-swap killer makes poor choices Message-ID: <YDacl5/AFzFA4nkg@kib.kiev.ua> 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 Wed, Feb 24, 2021 at 10:34:23AM -0700, Alan Somers wrote: > 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 I do not think so. The usable size of the swap is determined by the amount of swap metadata we pre-configure at boot time. Usually it is sized proportionally to the available physical memory, but you can override swap zones size manually with the knob. > 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). > -Alan
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