Date: Thu, 9 Aug 2018 09:52:11 -0700 From: Mark Millard <marklmi@yahoo.com> To: bob prohaska <fbsd@www.zefox.net> Cc: Mark Millard via freebsd-arm <freebsd-arm@freebsd.org>, Mark Johnston <markj@FreeBSD.org> Subject: Re: RPI3 swap experiments ["was killed: out of swap space" with: "v_free_count: 5439, v_inactive_count: 1"] Message-ID: <EF3F6D04-DD91-485B-AF2D-5D85C361A752@yahoo.com> In-Reply-To: <F61322C1-9B93-48B8-8FAB-269C256F5244@yahoo.com> References: <20180801034511.GA96616@www.zefox.net> <201808010405.w7145RS6086730@donotpassgo.dyslexicfish.net> <6BFE7B77-A0E2-4FAF-9C68-81951D2F6627@yahoo.com> <20180802002841.GB99523@www.zefox.net> <20180802015135.GC99523@www.zefox.net> <EC74A5A6-0DF4-48EB-88DA-543FD70FEA07@yahoo.com> <20180806155837.GA6277@raichu> <20180808153800.GF26133@www.zefox.net> <20180808204841.GA19379@raichu> <20180809065648.GB30347@www.zefox.net> <20180809152152.GC68459@raichu> <F61322C1-9B93-48B8-8FAB-269C256F5244@yahoo.com>
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[I'm adding what lead up to the first waiting for async swap write notice.] On 2018-Aug-9, at 9:44 AM, Mark Millard <marklmi at yahoo.com> wrote: > On 2018-Aug-9, at 8:21 AM, Mark Johnston <markj at FreeBSD.org> wrote: >=20 >> On Wed, Aug 08, 2018 at 11:56:48PM -0700, bob prohaska wrote: >>> On Wed, Aug 08, 2018 at 04:48:41PM -0400, Mark Johnston wrote: >>>> On Wed, Aug 08, 2018 at 08:38:00AM -0700, bob prohaska wrote: >>>>> The patched kernel ran longer than default but OOMA still halted = buildworld around >>>>> 13 MB. That's considerably farther than a default build world have = run but less than >>>>> observed when setting vm.pageout_oom_seq=3D120 alone. Log files = are at >>>>> = http://www.zefox.net/~fbsd/rpi3/swaptests/r337226M/1gbsdflash_1gbusbflash/= batchqueue/ >>>>>=20 >>>>> Both changes are now in place and -j4 buildworld has been = restarted.=20 >>>>=20 >>>> Looking through the gstat output, I'm seeing some pretty abysmal = average >>>> write latencies for da0, the flash drive. I also realized that my >>>> reference to r329882 lowering the pagedaemon sleep period was wrong = - >>>> things have been this way for much longer than that. Moreover, as = you >>>> pointed out, bumping oom_seq to a much larger value wasn't quite >>>> sufficient. >>>>=20 >>>> I'm curious as to what the worst case swap I/O latencies are in = your >>>> test, since the average latencies reported in your logs are high = enough >>>> to trigger OOM kills even with the increased oom_seq value. When = the >>>> current test finishes, could you try repeating it with this patch >>>> applied on top? = https://people.freebsd.org/~markj/patches/slow_swap.diff >>>> That is, keep the non-default oom_seq setting and modification to >>>> VM_BATCHQUEUE_SIZE, and apply this patch on top. It'll cause the = kernel >>>> to print messages to the console under certain conditions, so a log = of >>>> console output will be interesting. >>>=20 >>> The run finished with a panic, I've collected the logs and terminal = output at >>> = http://www.zefox.net/~fbsd/rpi3/swaptests/r337226M/1gbsdflash_1gbusbflash/= batchqueue/pageout120/slow_swap/ >>>=20 >>> There seems to be a considerable discrepancy between the wait times = reported >>> by the patch and the wait times reported by gstat in the first = couple of=20 >>> occurrences. The fun begins at timestamp Wed Aug 8 21:26:03 PDT = 2018 in >>> swapscript.log.=20 >>=20 >> The reports of "waited for swap buffer" are especially bad: during = those >> periods, the laundry thread is blocked waiting for in-flight swap = writes >> to finish before sending any more. Because the system is generally >> quite starved for clean pages that it can reuse, it's relying on swap >> I/O to clean more. If that fails, the system eventually has no = choice >> but to start killing processes (where the time period corresponding = to >> "eventually" is determined by vm.pageout_oom_seq). >=20 > Just for reference from=20 >=20 > = http://www.zefox.net/~fbsd/rpi3/swaptests/r337226M/1gbsdflash_1gbusbflash/= batchqueue/pageout120/slow_swap/swapscript.log >=20 > is some context for two of the swap buffer messages that gives some > information on the timing of the messages and some other activity: >=20 > Wed Aug 8 22:01:14 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 23912 1024664 2% > /dev/mmcsd0s3b 1048576 23892 1024684 2% > Total 2097152 47804 2049348 2% > Aug 8 21:36:13 www syslogd: last message repeated 1 times > Aug 8 21:36:13 www kernel: waited 3s for async swap write > 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 > 2 20 1 4 25.5 19 1216 41.4 0 0 = 0.0 29.3 mmcsd0 > 3 29 1 11 10.8 28 1244 23.9 0 0 = 0.0 18.7 da0 > 0 0 0 0 0.0 0 3 42.9 0 0 = 0.0 0.4 mmcsd0s2 > 2 20 1 4 25.6 19 1213 41.5 0 0 = 0.0 29.4 mmcsd0s3 > 0 0 0 0 0.0 0 3 43.0 0 0 = 0.0 0.4 ufs/rootfs > 2 20 1 4 25.6 19 1213 41.6 0 0 = 0.0 29.4 mmcsd0s3b > 2 20 1 11 10.9 19 1238 20.6 0 0 = 0.0 18.6 da0b > Wed Aug 8 22:01:24 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 37284 1011292 4% > /dev/mmcsd0s3b 1048576 36920 1011656 4% > Total 2097152 74204 2022948 4% > Aug 8 21:36:13 www syslogd: last message repeated 1 times > Aug 8 21:36:13 www kernel: waited 3s for async swap write > dT: 10.002s 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 8 0 0 4.7 8 693 41.7 0 0 = 0.0 12.2 mmcsd0 > 13 13 0 0 0.0 13 682 132.7 0 0 = 0.0 78.3 da0 > 0 8 0 0 4.7 8 693 41.8 0 0 = 0.0 12.2 mmcsd0s3 > 0 8 0 0 4.8 8 693 41.9 0 0 = 0.0 12.3 mmcsd0s3b > 5 7 0 0 0.0 7 676 79.5 0 0 = 0.0 40.1 da0b > Wed Aug 8 22:01:34 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 44680 1003896 4% > /dev/mmcsd0s3b 1048576 44132 1004444 4% > Total 2097152 88812 2008340 4% > Aug 8 21:36:13 www kernel: waited 3s for async swap write > Aug 8 22:01:30 www syslogd: last message repeated 1 times > Aug 8 22:01:41 www kernel: waited 10s for async swap write > Aug 8 22:01:41 www kernel: waited 6s for swap buffer > Aug 8 22:01:41 www kernel: waited 13s for async swap write > Aug 8 22:01:41 www kernel: waited 3s for swap buffer > Aug 8 22:01:41 www kernel: waited 12s for async swap write > Aug 8 22:01:41 www kernel: waited 10s for async swap write > Aug 8 22:01:41 www kernel: waited 3s for async swap write > dT: 10.001s 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 2 1 26 3.4 1 17 3.8 0 0 = 0.0 0.9 mmcsd0 > 0 4 3 61 3.8 2 70 5.7 0 0 = 0.0 1.7 da0 > 0 2 1 26 3.5 1 17 3.9 0 0 = 0.0 0.9 mmcsd0s3 > 0 1 0 0 0.0 1 17 4.0 0 0 = 0.0 0.4 mmcsd0s3a > 0 1 1 26 3.5 0 0 0.0 0 0 = 0.0 0.5 mmcsd0s3b > 0 2 2 54 3.8 0 0 0.0 0 0 = 0.0 0.9 da0b > 0 2 0 7 4.3 1 70 5.8 0 0 = 0.0 0.8 da0d > Wed Aug 8 22:01:51 PDT 2018 > Device 1K-blocks Used Avail Capacity > /dev/da0b 1048576 46156 1002420 4% > /dev/mmcsd0s3b 1048576 45480 1003096 4% > Total 2097152 91636 2005516 4% > Aug 8 22:01:41 www kernel: waited 10s for async swap write > Aug 8 22:01:41 www kernel: waited 3s for async swap write > dT: 10.002s 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 8 7 251 3.4 0 8 2.6 0 0 = 0.0 2.5 mmcsd0 > 0 9 7 186 4.2 2 77 7.4 0 0 = 0.0 3.6 da0 > 0 8 7 251 3.5 0 8 2.6 0 0 = 0.0 2.6 mmcsd0s3 > 0 0 0 0 0.0 0 8 2.7 0 0 = 0.0 0.1 mmcsd0s3a > 0 7 7 251 3.5 0 0 0.0 0 0 = 0.0 2.5 mmcsd0s3b > 0 7 7 184 4.2 0 0 0.0 0 0 = 0.0 2.7 da0b > 0 2 0 2 4.6 2 76 7.5 0 0 = 0.0 0.9 da0d Here is what leads to the first waiting for async swap write notice: dT: 10.002s 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 6 6.8 0 0 = 0.0 0.1 mmcsd0 0 1 0 1 2.2 1 9 4.6 0 0 = 0.0 0.2 da0 0 0 0 0 0.0 0 6 6.9 0 0 = 0.0 0.1 mmcsd0s3 0 0 0 0 0.0 0 6 6.9 0 0 = 0.0 0.1 mmcsd0s3a 0 1 0 1 2.3 1 9 5.2 0 0 = 0.0 0.2 da0d Wed Aug 8 21:25:32 PDT 2018 Device 1K-blocks Used Avail Capacity /dev/da0b 1048576 6288 1042288 1% /dev/mmcsd0s3b 1048576 6152 1042424 1% Total 2097152 12440 2084712 1% Aug 8 17:16:04 www syslogd: last message repeated 1 times Aug 8 17:18:59 www su[724]: bob to root on /dev/pts/0 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 0 4 0 0 0.0 4 74 5.2 0 0 = 0.0 1.1 mmcsd0 0 5 1 22 4.2 5 78 6.1 0 0 = 0.0 1.6 da0 0 4 0 0 0.0 4 74 5.3 0 0 = 0.0 1.2 mmcsd0s3 0 0 0 0 0.0 0 1 4.8 0 0 = 0.0 0.1 mmcsd0s3a 0 4 0 0 0.0 4 72 5.4 0 0 = 0.0 1.1 mmcsd0s3b 0 4 0 0 0.0 4 71 6.2 0 0 = 0.0 1.2 da0b 0 1 1 22 4.3 0 6 4.9 0 0 = 0.0 0.4 da0d Wed Aug 8 21:25:42 PDT 2018 Device 1K-blocks Used Avail Capacity /dev/da0b 1048576 6996 1041580 1% /dev/mmcsd0s3b 1048576 6876 1041700 1% Total 2097152 13872 2083280 1% Aug 8 17:16:04 www syslogd: last message repeated 1 times Aug 8 17:18:59 www su[724]: bob to root on /dev/pts/0 dT: 10.011s 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 50 0 0 0.0 50 740 4.1 0 0 = 0.0 13.0 mmcsd0 0 53 0 0 0.0 53 762 7.4 0 0 = 0.0 15.1 da0 0 50 0 0 0.0 50 740 4.2 0 0 = 0.0 13.2 mmcsd0s3 0 50 0 0 0.0 50 740 4.2 0 0 = 0.0 13.3 mmcsd0s3b 0 50 0 0 0.0 50 762 7.3 0 0 = 0.0 15.1 da0b Wed Aug 8 21:25:52 PDT 2018 Device 1K-blocks Used Avail Capacity /dev/da0b 1048576 15512 1033064 1% /dev/mmcsd0s3b 1048576 14800 1033776 1% Total 2097152 30312 2066840 1% Aug 8 17:16:04 www syslogd: last message repeated 1 times Aug 8 17:18:59 www su[724]: bob to root on /dev/pts/0 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 0 35 0 0 0.0 35 1509 11.2 0 0 = 0.0 20.3 mmcsd0 0 43 0 3 44.8 43 1346 50.1 0 0 = 0.0 55.9 da0 0 35 0 0 0.0 35 1506 11.4 0 0 = 0.0 20.4 mmcsd0s3 0 35 0 0 0.0 35 1503 11.4 0 0 = 0.0 20.4 mmcsd0s3b 0 0 0 3 44.8 0 6 3.3 0 0 = 0.0 0.5 da0a 0 35 0 0 0.0 35 1336 54.3 0 0 = 0.0 56.5 da0b 0 0 0 0 0.0 0 3 1433 0 0 = 0.0 14.3 da0d Wed Aug 8 21:26:03 PDT 2018 Device 1K-blocks Used Avail Capacity /dev/da0b 1048576 29448 1019128 3% /dev/mmcsd0s3b 1048576 30540 1018036 3% Total 2097152 59988 2037164 3% Aug 8 17:18:59 www su[724]: bob to root on /dev/pts/0 Aug 8 21:25:57 www kernel: waited 3s for async swap write dT: 10.002s 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 1 0 1 3.8 1 77 17.5 0 0 = 0.0 1.1 mmcsd0 0 2 0 7 3.5 2 84 14.9 0 0 = 0.0 1.2 da0 0 0 0 1 3.9 0 3 7.4 0 0 = 0.0 0.1 mmcsd0s2 0 1 0 0 0.0 1 74 18.4 0 0 = 0.0 1.0 mmcsd0s3 0 0 0 1 4.0 0 3 7.5 0 0 = 0.0 0.1 ufs/rootfs 0 1 0 0 0.0 1 9 13.5 0 0 = 0.0 0.8 mmcsd0s3a 0 1 0 0 0.0 1 65 23.3 0 0 = 0.0 0.8 mmcsd0s3b 0 1 0 1 2.4 1 77 21.6 0 0 = 0.0 0.8 da0b 0 1 0 6 3.8 0 8 5.2 0 0 = 0.0 0.4 da0d > Based on these latencies, I think the system is behaving more or less = as > expected from the VM's perspective. I do think the default oom_seq = value > is too low and will get that addressed in 12.0. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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