Date: Fri, 14 Sep 2018 22:08:43 -0700 From: bob prohaska <fbsd@www.zefox.net> To: Mark Millard <marklmi@yahoo.com> Cc: freebsd-arm@freebsd.org, bob prohaska <fbsd@www.zefox.net> Subject: Re: RPI3 swap experiments (r338342 with vm.pageout_oom_seq="1024" and 6 GB swap) Message-ID: <20180915050842.GA65045@www.zefox.net> In-Reply-To: <075BD4BB-CAFB-4C9B-809A-10901522D1ED@yahoo.com> References: <20180815013612.GB51051@www.zefox.net> <CANCZdfoB_AcidFpKT_ZmZWUFnmC4Bw55krK%2BMqEmmj=f9KMQ2Q@mail.gmail.com> <20180815225504.GB59074@www.zefox.net> <20180901230233.GA42895@www.zefox.net> <20180906003829.GC818@www.zefox.net> <FB333A71-47D8-4038-9983-116DA80FC952@yahoo.com> <20180906051520.GB3482@www.zefox.net> <059D2FED-6E7C-4FEF-8807-8D4A0D0B3E26@yahoo.com> <20180906155858.GA5980@www.zefox.net> <075BD4BB-CAFB-4C9B-809A-10901522D1ED@yahoo.com>
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On Thu, Sep 06, 2018 at 10:32:50AM -0700, Mark Millard wrote: > > It appears to me that for the devices that you are currently using, > you are better off for elapsed time having the swap only on the > sdcard. > In practical terms this seems true. I set up a 16 GB Sandisk Ultra Plus microSD card with a single partition for / and 1.8 GB of swap at the end, running r338572 with vm.pageout_oom_seq="1024". It finished -j4 buildworld successfully but ran out of space in buildkernel. 32 GB would have been far more than sufficient. There were many spurious "indefinite wait" and a few "out of swap" warnings on the console, but nothing came of them. A faster microSD card might have avoided the warnings entirely, the Ultra Plus isn't the fastest horse in the stable. I neglected to salvage the buildworld timing, but it was under 24 hours. Aftr moving /usr/src to a separate USB3.0 flash drive I repeated that test, adding experiments with swap on the same USB flash drive and swap on a second USB flash drive. All the tests succeeded, none sufficiently faster to justify the expense and complication of a second storage device. The log files are at http://www.zefox.net/~fbsd/rpi3/swaptests/r338572/ if anybody's interested. It might make sense to divide storage to protect valuable data from wearout, but I've not seen any evidence (knock on wood!) that wearout of flash media is a serious problem with the Pi. Setting up a physical swap partition by hand at the end of the microSD card is fairly difficult. If it could be automated through the machinery invoked by /firstboot that would be a useful feature. Thanks to all (Mark especially) for reading and guiding! bob prohaska
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