GPT vs MBR for swap devices

Mark Millard marklmi at yahoo.com
Mon Jun 18 23:42:25 UTC 2018



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.

There is an earlier example of something similar, again for
da0 and da0d having the large ms/w (and ms/r here):

Mon Jun 18 09:32:00 PDT 2018
Device          1K-blocks     Used    Avail Capacity
/dev/da0b         1048576     3516  1045060     0%
/dev/mmcsd0s3b    1048576     3604  1044972     0%
Total             2097152     7120  2090032     0%
dT: 10.010s  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      0    0.0      1      8    5.4      0      0    0.0    0.2  mmcsd0
    6      1      0      1  373.9      1     18   1070      0      0    0.0   73.6  da0
    0      0      0      0    0.0      0      7    6.1      0      0    0.0    0.1  mmcsd0s2
    0      0      0      0    0.0      0      7    6.1      0      0    0.0    0.1  ufs/rootfs
    4      1      0      1  373.9      1     18   1243      0      0    0.0   73.6  da0d
Mon Jun 18 09:32:20 PDT 2018
Device          1K-blocks     Used    Avail Capacity
/dev/da0b         1048576     3516  1045060     0%
/dev/mmcsd0s3b    1048576     3604  1044972     0%
Total             2097152     7120  2090032     0%



===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)



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