Date: Sun, 2 Sep 2018 01:32:17 -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") Message-ID: <20180902083217.GA44384@www.zefox.net> In-Reply-To: <F3AF3A89-322E-4048-A758-4276C1A1BEA0@yahoo.com> References: <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> <20180815225504.GB59074@www.zefox.net> <20180901230233.GA42895@www.zefox.net> <F3AF3A89-322E-4048-A758-4276C1A1BEA0@yahoo.com>
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On Sat, Sep 01, 2018 at 07:51:54PM -0700, Mark Millard wrote: > > > On 2018-Sep-1, at 4:02 PM, bob prohaska <fbsd at www.zefox.net> wrote: > > > On Wed, Aug 15, 2018 at 03:55:04PM -0700, bob prohaska wrote: > >> > >> When I started this goose chase, after zero problems with RPI2, I thought the > >> issue was arm64-related and might be of some fundamental importance. > >> > >> Thanks to many people I now understand it's a confluence of USB and flash memory > >> artifacts, made evident by the demands of clang6. Elsewhere I noted that I'm seeking > >> "the robustness of a Mars rover, using a rack server OS on a cellphone motherboard". > >> > > > > With r338342 and > > vm.pageout_oom_seq="1024" > > in /boot/loader.conf the RPI3 is a bit closer to a Mars Rover. > > No panics, crashes or USB errors, -j4 buildworld runs to completion. > > When swap usage goes over about 50% the system slows, but doesn't give up. > > There are six 1 GB swap partitions available, 3 on USB and 3 on microSD. > > > > Log files are at > > http://www.zefox.net/~fbsd/rpi3/swaptests/r338342/ > > for the combinations tried so far. > > http://www.zefox.net/~fbsd/rpi3/swaptests/r338342/2gbsd/swapscript.log > > shows things like: > > dT: 10.043s w: 10.000s > L(q) ops/s r/s kBps ms/r w/s kBps ms/w d/s kBps ms/d %busy Name > 0 126 19 122 2.3 107 2034 3.3 0 0 0.0 29.2 da0 > 0 67 0 0 0.0 67 1126 2.5 0 0 0.0 16.6 da0f > 0 59 19 122 2.3 40 909 4.7 0 0 0.0 14.7 da0g > > as well as: > > dT: 10.004s w: 10.000s > L(q) ops/s r/s kBps ms/r w/s kBps ms/w d/s kBps ms/d %busy Name > 4 412 32 324 11.2 380 2945 7.9 0 0 0.0 80.2 mmcsd0 > 0 1 1 26 4.7 0 0 0.0 0 0 0.0 0.4 da0 > 4 412 32 324 11.5 380 2945 8.0 0 0 0.0 80.8 mmcsd0s2 > 2 205 15 160 10.6 190 1453 8.0 0 0 0.0 78.7 mmcsd0s2d > 2 207 17 165 12.3 190 1491 8.0 0 0 0.0 78.6 mmcsd0s2e > 0 0 0 0 0.0 0 1 17.5 0 0 0.0 0.2 mmcsd0s2a > 0 0 0 0 0.0 0 1 17.6 0 0 0.0 0.2 ufs/rootfs > 0 1 1 26 4.8 0 0 0.0 0 0 0.0 0.4 da0g > > It is not clear what partitions were in use for what types of > data. da0f, da0g, mmcsd0s2d, and mmcsd0s2e: are they all > swap partitions? If yes, then the the test log does not appear > to be a "2gbsd" test. > The swap partitions are identified in the swapinfo data following the gstat and date output, in this case mmcsd0s2d and -e. /var is on da0e, /tmp is on da0f and /usr is on da0g. I do apologize, that was ambiguous. It's in the readme for that revision number now. > > Ignoring such points: Are these tests using the same devices that logged > errors to the console in all that prior testing? > > If yes: Having such errors stop is potentially interesting. > Yes, this is the same pair of devices which produced the flood of USB errors when either deliberately run out of swap or used with OOMA turned off. The USB flash drive is a Sandisk SDCZ800-064G, nominally a "USB3.1" device. It's quite clear that I/O congestion badly affects performance, but I'm not convinced it's exclusively swap I/O that causes trouble. Sometimes it looks as if traffic to /usr gums up the works and takes minutes to unjam. In any case, the fact that the system rights itself and keeps working is encouraging. It's also interesting, though probably not useful, to note that 4 GB of swap seems to cause no trouble, at least in this configuration. I haven't tried 6 GB yet. Thanks for reading, bob prohaska
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