Date: Mon, 13 Feb 2017 19:34:53 -0800 From: Mark Millard <markmi@dsl-only.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: wynkoop@wynn.com, freebsd-arm@freebsd.org Subject: Re: Out of swap - NOT Message-ID: <75FA953B-4F23-4FF9-92D9-B78BA890EEA6@dsl-only.net> In-Reply-To: <20170214032036.GR2092@kib.kiev.ua> References: <20170211022800.14138f68@pearl> <CA%2BWntOtWk8ALoVfSUJjB-7iE5iW2sOYQXKcMqDo35T92RuzvYA@mail.gmail.com> <assp.0217334a41.20170213164604.0110b21b@pearl> <20170214032036.GR2092@kib.kiev.ua>
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On 2017-Feb-13, at 7:20 PM, Konstantin Belousov <kostikbel at gmail.com> = wrote: > On Mon, Feb 13, 2017 at 04:46:04PM -0500, Brett Wynkoop wrote: >> On Mon, 13 Feb 2017 15:55:11 -0500 >> Joe Nosay <superbisquit at gmail.com> wrote: >>=20 >>> Is it possible to place the swap on a separate disk such as a usb? >>=20 >> Yes, but I am not sure what difference that will make. I would think = a >> swapfile is a swapfile. Yes I am swapping on a file because the = image >> autogrew the filesystem on first boot, so no chance to set up a >> partition. > swapfile write requires the write request to come through the = filesystem > write path, which might require the filesystem to allocate more memory > and read some data. E.g. it is known that any ZFS write request > allocates memory, and that write request on large UFS file might = require > allocating and reading an indirect block buffer to find the block = number > of the written block, if the indirect block was not yet read. >=20 > As result, swapfile swapping is more prone to the trivial and = unavoidable > deadlocks where the pagedaemon thread, which produces free memory, = needs > more free memory to make a progress. Swap write on the raw partition = over > simple partitioning scheme directly over HBA are usually safe, while = e.g. > zfs over geli over umass is the worst construction. Thanks for the explanation of bugzilla 206038: 11.0-CURRENT -r293227 (and others) arm (rpi2/BeagleBone Black) amd64 etc: swapfile usage hangs; swap partition works I'll copy your text into the comments for that submittal. =3D=3D=3D Mark Millard markmi at dsl-only.net
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