Date: Mon, 18 Jun 2018 17:55:20 -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: GPT vs MBR for swap devices Message-ID: <20180619005519.GB81275@www.zefox.net> In-Reply-To: <A8D00616-ADA7-4A33-8787-637AFEF547CF@yahoo.com> References: <7AB401DF-7AE4-409B-8263-719FD3D889E5@yahoo.com> <20180618230419.GA81275@www.zefox.net> <A8D00616-ADA7-4A33-8787-637AFEF547CF@yahoo.com>
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On Mon, Jun 18, 2018 at 04:42:21PM -0700, Mark Millard wrote: > > > On 2018-Jun-18, at 4:04 PM, bob prohaska <fbsd at www.zefox.net> wrote: > > > On Sat, Jun 16, 2018 at 04:03:06PM -0700, Mark Millard wrote: > >> > >> Since the "multiple swap partitions across multiple > >> devices" context (my description) is what has problems, > >> it would be interesting to see swapinfo information > >> from around the time frame of the failures: how much is > >> used vs. available on each swap partition? Is only one > >> being (significantly) used? The small one (1 GiByte)? > >> > > There are some preliminary observations at > > > > http://www.zefox.net/~fbsd/rpi3/swaptests/newtests/1gbusbflash_1gbsdflash_swapinfo/1gbusbflash_1gbsdflash_swapinfo.log > > > > If you search for 09:44: (the time of the OOM kills) it looks like > > both swap partitions are equally used, but only 8% full. > > > > At this point I'm wondering if the gstat interval (presently 10 seconds) > > might well be shortened and the ten second sleep eliminated. On the runs > > that succeed swap usage changes little in twenty seconds, but the failures > > seem to to culminate rather briskly. > > One thing I find interesting somewhat before the OOM activity is > the 12355 ms/w and 12318 ms/w on da0 and da0d that goes along > with having 46 or 33 L(q) and large %busy figures in the same > lines --and 0 w/s on every line: > > Mon Jun 18 09:42:05 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 3412 1045164 0% > /dev/mmcsd0s3b 1048576 3508 1045068 0% > Total 2097152 6920 2090232 0% > 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 0 0 0 0.0 0 9 10.8 0 0 0.0 0.1 mmcsd0 > 46 0 0 0 0.0 0 16 12355 0 0 0.0 85.9 da0 > 0 0 0 0 0.0 0 9 10.8 0 0 0.0 0.1 mmcsd0s3 > 0 0 0 0 0.0 0 9 10.8 0 0 0.0 0.1 mmcsd0s3a > 33 0 0 0 0.0 0 22 12318 0 0 0.0 114.1 da0d > Mon Jun 18 09:42:25 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 3412 1045164 0% > /dev/mmcsd0s3b 1048576 3508 1045068 0% > Total 2097152 6920 2090232 0% > > > The kBps figures for the writes are not very big above. > If it takes 12 seconds to write, I can understand the swapper getting impatient.... However, the delay is on /usr, not swap. In the subsequent 1 GB USB flash-alone test case at http://www.zefox.net/~fbsd/rpi3/swaptests/newtests/1gbusbflash_swapinfo/1gbusbflash_swapinfo.log the worst-case seems to be at time 13:45:00 dT: 13.298s 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 0 0 0 0.0 0 5 5.5 0 0 0.0 0.1 mmcsd0 9 84 0 0 0.0 84 1237 59.6 0 0 0.0 94.1 da0 0 0 0 0 0.0 0 5 5.5 0 0 0.0 0.1 mmcsd0s3 0 0 0 0 0.0 0 5 5.6 0 0 0.0 0.1 mmcsd0s3a 5 80 0 0 0.0 80 1235 47.2 0 0 0.0 94.1 da0b 4 0 0 0 0.0 0 1 88.1 0 0 0.0 0.7 da0d Mon Jun 18 13:45:00 PDT 2018 Device 1K-blocks Used Avail Capacity /dev/da0b 1048576 22872 1025704 2% 1.2 MB/s writing to swap seems not too shabby, hardly reason to kill a process. Thus far I'm baffled. Any suggestions? Thanks for reading! bob prohaska
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