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Date:      Tue, 31 Jul 2018 10:51:51 -0700
From:      Mark Millard <marklmi@yahoo.com>
To:        bob prohaska <fbsd@www.zefox.net>
Cc:        Trev <freebsd-arm@sentry.org>, freebsd-arm@freebsd.org
Subject:   Re: RPI3 swap experiments
Message-ID:  <908FB299-07CF-4E88-9C18-298CA357AD01@yahoo.com>
In-Reply-To: <20180731153531.GA94742@www.zefox.net>
References:  <bc8da02c-4465-9634-6fd0-0af4c63aa49d@sentry.org> <20180723063526.GA45726@www.zefox.net> <AB5EE2E4-B2FD-4CA9-A993-04C2A4BE10AE@yahoo.com> <20180723155311.GB45726@www.zefox.net> <4ED9B658-A5A8-4BA6-9412-EBB7150B4B66@yahoo.com> <20180723190257.GA47869@www.zefox.net> <76BCFCB9-1071-4557-9FDE-017444ADBF42@yahoo.com> <20180725232453.GA57716@www.zefox.net> <20180731054712.GA92917@www.zefox.net> <d17be735-4d7e-73b6-4af1-a64470bc9e32@sentry.org> <20180731153531.GA94742@www.zefox.net>

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On 2018-Jul-31, at 8:35 AM, bob prohaska <fbsd at www.zefox.net> wrote:

> On Tue, Jul 31, 2018 at 10:31:33PM +1000, Trev wrote:
>> bob prohaska wrote on 31/07/2018 15:47:
>>=20
>>> It would be most interesting to see what happens if OOMA
>>> could be turned off. Is that possible?
>>=20
>> Possibly, but you might find you're treating the symptom(s) rather =
than=20
>> the cause(s) ... something must be triggering the condition whether=20=

>> correctly or not.
>=20
> That's my point. To determine if OOMA is triggered correctly or not. =
I'm starting
> to think not.
>=20
> The reason is the dependency on swap layout (mixed USB/microSD vs all =
one or the
> other) and the fact that OOMA kills don't seem to coincide with =
periods of=20
> maximum storage read/write delay, which is the conventional =
explanation for
> why OOMA kills happen in the first place. If turning off OOMA allows =
buildworld
> to complete successfully it suggests OOMA isn't correctly implemented.=20=


Your rpi2 report said:

> In this particular case all swap is on USB, in a single
> 2 GB partition.

which for that example indicates that swap layout being split
was not involved. (But there is the potential too-large issue.)

Have you had other examples of non-split swap layout getting
OOMA kills? If yes, what types of contexts? [Especially any that
do not have observed huge latencies or to evidence of device
failures (retries required).] Any on rpi3? Any others on rpi2?

As for swap use, do you have any tmpfs or other files systems
that are memory based that also use swap if they grow too
big (and are configured to allow such growth)?


=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)




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