Date: Wed, 15 Aug 2018 06:21:42 -0500 From: Jedi Tek'Unum <jedi@jeditekunum.com> To: Warner Losh <imp@bsdimp.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: RPI3 swap experiments (grace under pressure) Message-ID: <B2F29828-7FF6-42C8-B4B7-1EB910B50C8C@jeditekunum.com> In-Reply-To: <CANCZdfoB_AcidFpKT_ZmZWUFnmC4Bw55krK%2BMqEmmj=f9KMQ2Q@mail.gmail.com> References: <20180812173248.GA81324@phouka1.phouka.net> <20180812224021.GA46372@www.zefox.net> <B81E53A9-459E-4489-883B-24175B87D049@yahoo.com> <20180813021226.GA46750@www.zefox.net> <0D8B9A29-DD95-4FA3-8F7D-4B85A3BB54D7@yahoo.com> <FC0798A1-C805-4096-9EB1-15E3F854F729@yahoo.com> <20180813185350.GA47132@www.zefox.net> <FA3B8541-73E0-4796-B2AB-D55CE40B9654@yahoo.com> <20180814014226.GA50013@www.zefox.net> <CANCZdfqFKY3Woa%2B9pVS5hika_JUAUCxAvLznSS4gaLq2kKoWtQ@mail.gmail.com> <20180815013612.GB51051@www.zefox.net> <CANCZdfoB_AcidFpKT_ZmZWUFnmC4Bw55krK%2BMqEmmj=f9KMQ2Q@mail.gmail.com>
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On Aug 14, 2018, at 11:26 PM, Warner Losh <imp@bsdimp.com> wrote: >=20 > So I think what's well tuned for the gear that's in a server doing > traditional database and/or compute workloads may not be so well tuned = for > the RPi3 when you put NAND that can vary a lot in performance, as well = as > have fast reads and slow writes when the mix isn't that high. The = system > can be tuned to cope, but isn't tuned that way out of the box. When there are no-win situations due to restrictive hardware then the = best solution is likely documentation encouraging people to avoid such = hardware. I doubt this is worth the effort of developing a kludge as one would = expect that these limitations will go away as hardware evolves - = rapidly. If people want to do things like -j4 on this kind of hardware then they = are asking for trouble. Might as well recommend swap over nfs. Surely not something one would = recommend on normal hardware but in this case it probably isn=E2=80=99t = any worse than slow NAND. However, I remain of the opinion that when people try to use hardware = unable to achieve minimal behavior that they should just suffer the = unresponsiveness. Surely thresholds can be recognized and warning syslog = messages provided. I=E2=80=99d rather have it sluggish than dying at = random times. I=E2=80=99ve not looked at OOM details on FreeBSD=E2=80=A6 Is there a = special signal sent to the victim before its killed? A quick glance at = the signal list says no. Of course that would introduce even more = complexity as the victim would need some reprieve time to be able to do = something with it. Even AIX had this in the =E2=80=9880s. My experience = back then was that it was better than nothing but not terribly useful.
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