Date: Sat, 13 Oct 2018 15:19:23 +0100 From: Steve O'Hara-Smith <steve@sohara.org> To: freebsd-questions@freebsd.org Cc: RW <rwmaillists@googlemail.com> Subject: Re: swap to a sparse file Message-ID: <20181013151923.edca08f54b508dc98b91cb37@sohara.org> In-Reply-To: <20181013145247.0a4b7f05@gumby.homeunix.com> References: <20181011014705.GA17798@admin.sibptus.ru> <20181011085114.bfcdb701b3644728a71eaa38@sohara.org> <20181012193633.7dc32f86@gumby.homeunix.com> <20181013081118.9e8632405e555c3bf2f9a722@sohara.org> <20181013145247.0a4b7f05@gumby.homeunix.com>
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On Sat, 13 Oct 2018 14:52:47 +0100 RW via freebsd-questions <freebsd-questions@freebsd.org> wrote: > On Sat, 13 Oct 2018 08:11:18 +0100 > Steve O'Hara-Smith wrote: > > > On Fri, 12 Oct 2018 19:36:33 +0100 > > RW via freebsd-questions <freebsd-questions@freebsd.org> wrote: > > > > > On Thu, 11 Oct 2018 08:51:14 +0100 > > > Steve O'Hara-Smith wrote: > > > > > > > On Thu, 11 Oct 2018 08:47:05 +0700 > > > > Victor Sudakov <vas@mpeks.tomsk.su> wrote: > > > > > > > > > Is there any good reason I can't just "truncate -s2G /swap0" and > > > > > make the swap a sparse file? > > > > > > > > Just one - if the space isn't there when the system needs > > > > it there will be a panic. > > > > > > Is that really the only reason? I've not paid much attention, but > > > the warnings I've heard about this have made it sound a lot worse. > > > > There's not much worse the system can do than panic, other > > than deadlock which might happen if memory needs to be allocated in > > order to add blocks to the file. IIRC swap on a zvol can deadlock > > that way. > > > Yes, but filling up a drive is relatively avoidable - particularly if > there's space reserved for root. True enough, although if you are counting on having the space available then pre-allocating it is a strong guarantee and prevents the performance penalty of adding a block to a file as an overhead of swapping. -- Steve O'Hara-Smith <steve@sohara.org>
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