Date: Wed, 18 Jul 2018 12:09:51 -0700 From: bob prohaska <fbsd@www.zefox.net> To: Mark Millard <marklmi@yahoo.com> Cc: freebsd-arm@freebsd.org Subject: Re: RPI3 swap experiments Message-ID: <20180718190951.GB27481@www.zefox.net> In-Reply-To: <F31DD1B5-42A8-4A48-A771-D38479604FD5@yahoo.com> References: <20180629233937.GC35717@www.zefox.net> <0f137e06-214a-3e8c-a216-f061ec04ac2c@sentry.org> <20180630005145.GA43801@www.zefox.net> <6f3406e2-71f3-d0c2-2b65-703e1a1d3c25@sentry.org> <8e92b2b7-da61-3efb-7231-9fac76b2c1d4@sentry.org> <ba33d8a7-a849-3893-8016-0765ebe1c51f@sentry.org> <2deaaec3-f78f-0b09-5ca7-27e14c6979f9@sentry.org> <20180704004554.GA61273@www.zefox.net> <20180718060650.GA24566@www.zefox.net> <F31DD1B5-42A8-4A48-A771-D38479604FD5@yahoo.com>
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On Wed, Jul 18, 2018 at 07:42:13AM -0700, Mark Millard wrote: > > > On 2018-Jul-17, at 11:06 PM, bob prohaska <fbsd at www.zefox.net> wrote: > > > It appears that some progress has been made in getting swap working reasonably > > on the RPI3. A -j4 buildworld attempt running r336356 to compile 336431 failed > > with "out of swap" but the worst read and write delays were less than 5 seconds, > > a marked improvement over previous examples. > > Attributing the time variations that have been observed mostly to FreeBSD and not > mostly to the device at issue seems to have little or no evidence to support it. > Possibly a fair objection. This test is with a USB3.0 flash drive. I'll repeat soon as possible with a USB3.1 device, which in the past reported much greater (15 second) delays. > > In this case swap was split, 2 each 1GB partitions on USB flash plus 1 GB on the > > microSD card. Previous attempts using 3 each 1 GB partitions on USB flash have been > > repeatedly successful, while a single attempt using 3 each 1GB partitions on microSD > > failed. > > The more swap partitions (or space?) not on a /dev/mmcsd0s* the less of the > activity that /dev/mmcsd0 handles and likely the more time it tends to have > between explicit operations to do internal housekeeping before the next > explicit operation. > > So the better approximation to not using /dev/mmcsd0 at all might not be > all that much of a surprise at having less of a problem on the device > (or a problem less often). > In earlier tests (same card type) putting _all_ swap on microSD (along with /tmp) avoided OOMA kills. Dependable mischief seems to come when swap is on both microSD and USB. It's understood that USB and Ethernet share I/O hardware, but I thought microSD was at least somewhat independent. Is this wrong? Thanks for reading, bob prohaska
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