RPI3 swap experiments
Mark Millard
marklmi at yahoo.com
Tue Jul 31 07:02:17 UTC 2018
On 2018-Jul-30, at 11:44 PM, Mark Millard <marklmi at yahoo.com> wrote:
> On 2018-Jul-30, at 10:47 PM, bob prohaska <fbsd at www.zefox.net> wrote:
>
>> OOMA is still killing processes in -j4 buildworld sessions for no obvious reason
>> when using mixed USB/microSD swap. The most recent experiment is with r336877
>> rebuilding itself from a clean start.
>>
>> The various log files are at
>> http://www.zefox.net/~fbsd/rpi3/swaptests/r336877/
>> The OOMA kills occur around two hours after
>> the worst read/write delays, which are in the low tens
>> of seconds. Perhaps most curiously, the long delays
>> don't appear to involve swap partitions.
>>
>> Similar problems now seem present with the RPI2 on
>> 11-stable. The first failure was with r335398 trying
>> to compile 336871. Buildworld has been backed down to
>> -j2 and restarted in the hope it'll eventually succeed.
>> In this particular case all swap is on USB, in a single
>> 2 GB partition.
>
> My records indicate (from old boot messages and reported
> in past list messages):
>
> rpi2: . . . exceeds maximum recommended amount (411488 pages).
> rpi3: . . . exceeds maximum recommended amount (925680 pages).
>
> 411488*4K Bytes = 1,685,454,848 Bytes for rpi2 (older V1.1 armv7
> variant). In other words: you have more swap than is recommended
> for such a context because of fragmentation issues and such for
> overhead information related to keeping track of swapping/paging.
>
> I suggest trying not exceeding the 1,685,454,848 figure for the
> rpi2 context, just as a cross check. May be 411000*4K Bytes,
> so 1,683,456,000 Bytes, avoiding being right at the boundary?
>
> 925680*4K Bytes = 3,791,585,280 Bytes for rpi3.
>
> Are thew drives involved different ones than used with the
> rpi3 experiments? (Just curious.)
>
>
>> It would be most interesting to see what happens if OOMA
>> could be turned off. Is that possible?
>
> If the code reaches conditions which initiate OOMA now, what
> would proposed alternate action be? As stands if OOMA itself
> fails to happen, my guess would be the kernel would panic,
> deadlock, or livelock in some way. Simply having OOMA not
> attempted would likely be the same as OOMA failing unless
> more than disabling OOMA was done.
>
> (I'm no expert at such so if someone that knows makes a claim,
> believe them instead of me.)
Looking around, there have been other rpi2 figures that I've
seen and reported on the lists, for example:
exceeds maximum recommended amount (405460 pages)
exceeds maximum recommended amount (469280 pages)
So if you do not have a specific figure from a boot message,
your might want:
400000*4K Bytes = 1,638,400,000 Bytes
or even somewhat less. If you have a specific figure from a
current boot message for the same version, I'd go somewhat
less than that figure scaled to Bytes.
===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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