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Date:      Wed, 27 Jun 2018 18:12:53 -0700
From:      Mark Millard <marklmi@yahoo.com>
To:        bob prohaska <fbsd@www.zefox.net>
Cc:        freebsd-arm@freebsd.org
Subject:   Re: RPI3 swap experiments
Message-ID:  <C6303FC5-B412-472C-98E4-9A1E45C38535@yahoo.com>
In-Reply-To: <20180627194217.GA27793@www.zefox.net>
References:  <20180626052451.GA17293@www.zefox.net> <CANCZdfpXyzxzOZ8pqcRtuFsxYx5Jjs9oSL1ok2sGVPHdiB0qVQ@mail.gmail.com> <201806261040.w5QAeBKq035183@donotpassgo.dyslexicfish.net> <A6986B21-FF6E-48F5-9F3A-06B3D2A92C55@yahoo.com> <20180626151843.GD17293@www.zefox.net> <3525D7C7-F848-45A1-BD85-2DAC895DF48C@yahoo.com> <20180626222834.GA20270@www.zefox.net> <28012DFB-37A0-461A-BB62-CD3EE61E82F0@yahoo.com> <20180627054027.GA22144@www.zefox.net> <CC72E766-03CB-476C-8F2B-DAAC266CE63D@yahoo.com> <20180627194217.GA27793@www.zefox.net>

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On 2018-Jun-27, at 12:42 PM, bob prohaska <fbsd at www.zefox.net> wrote:

> On Tue, Jun 26, 2018 at 11:30:52PM -0700, Mark Millard wrote:
>> On 2018-Jun-26, at 10:40 PM, bob prohaska <fbsd at www.zefox.net> =
wrote:
>>=20
>> . . .
>> For (A), have you tried any examples of:
>>=20
>> sufficient swap on mmcsd0 (or other such) with no swap
>> on da0 (but /usr and /var on /dev/da0)?
> Yes, that is the configuration which completes successfully.
>>=20
>> If yes, did you check on if there were /dev/da0 errors
>> logged? What, if any, /dev/da0 errors where logged?
>> None?
> Correct, no errors on da0 when -j4 buildworld is successful.

Good to know. Thanks.

>> For (B), have you tried any examples of:
>>=20
>> insufficient swap on (say) mmcsd0 and no use of the
>> /dev/da0 drive that has reported errors at all,
>> /usr/ and /var not on mmcsd0 (or whatever was used
>> for swap) either? Did some drive end up reporting
>> errors? Which? Did the system still crash as well?
>>=20
> I think this is the standard test case:
> /usr and /var on /dev/da0
> /tmp on /dev/mmcsd0s3a
> swap on /dev/mmcsd0s3b
>=20
> This configuration has crashed reliably with errors on /dev/da0 but no =
other "disk" errors.
> Did I understand the question correctly?

I intended for "no use of /dev/da0" to indicate
that not even /usr or /var were from the device
that has been logging the errors. For example:
having /usr or /var on the mechanical disk and
the known-problem disk not connected at all.

This would get either no-errors or some other
device would get errors, possibly the mechanical
disk (if that was the type used for a test).

>>=20
>>=20
>> Have such test-context combinations been tried?
>>=20
>> Without any logs to look at for such alternatives, I
>> can not try to compare/contrast such to the others
>> examples.
>>=20
>=20
> Understood. The matrix of test conditions is not completely filled,
> and the test of different media for /dev/da0 has not yet been made.
> I'd like to play with stress2 and ports/sysutils/stress before doing
> that.

It would be handy for something simpler than buildworld to be
able to induce some of the types of problems, for sure.

> There is a new, successful -j4 buildworld swapuse.log for the case
> of 3 GB of USB flash swap at
>=20
> http://www.zefox.net/~fbsd/rpi3/swaptests/r335576/3gbusbflash/
>=20

I do not see a console.log or notes about the console messages
(or lack of such). Where there any messages there of note? No
device errors? Was such checked for?

> The system is now up to r335655 and I'm trying to replicate=20
> earlier crash behavior before proceeding further.=20
>=20

Sounds good.

I will note that the following might help memory handling
for your context (small memory context):

Author: alc
Date: Tue Jun 26 18:29:56 2018
New Revision: 335674
URL: https://svnweb.freebsd.org/changeset/base/335674

Log:
  Update the physical page selection strategy used by vm_page_import() =
so
  that it does not cause rapid fragmentation of the free physical =
memory.
 =20
  Reviewed by:	jeff, markj (an earlier version)
  Differential Revision:	https://reviews.freebsd.org/D15976


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




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