Date: Wed, 23 Jul 2014 03:20:02 +0200 From: Polytropon <freebsd@edvax.de> To: Warren Block <wblock@wonkity.com> Cc: FreeBSD-Questions <freebsd-questions@freebsd.org> Subject: Re: How much swap space for a 32 GB RAM system? Message-ID: <20140723032002.2a34a6b1.freebsd@edvax.de> In-Reply-To: <alpine.BSF.2.11.1407221119110.80885@wonkity.com> References: <53CE8BB8.7030303@qeng-ho.org> <20140722191548.e3945a1e.freebsd@edvax.de> <alpine.BSF.2.11.1407221119110.80885@wonkity.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, 22 Jul 2014 11:22:07 -0600 (MDT), Warren Block wrote: > On Tue, 22 Jul 2014, Polytropon wrote: > > > On Tue, 22 Jul 2014 17:05:12 +0100, Arthur Chance wrote: > >> I'm getting a new machine with 32 GB of memory. The old "twice physical > >> memory" sizing seems ridiculous, so how big should I make swap? Do I > >> even need swap with this much memory? > > > > Need? Probably not, but you _never_ know... So preparing > > a file-backed swap could be a nice solution: you do not > > have to dedicate a fixed size partition for swap, and > > depending on your disk setup (maybe SSD?) the speed (_if_ > > it gets in use) will be good enough. In order to do this, > > you use dd to create a sparse file, > > File yes, sparse file no. Bad Things(TM) may happen with a sparse file. Okay, probably wrong terminology here. :-) This is how I did it: In order to keep things simple, I added the following to /etc/rc.local: SWAP="/swapfile.tmp" /bin/rm -f $SWAP /bin/dd if=/dev/zero of=$SWAP bs=16m seek=1k count=0 /sbin/mdconfig -a -t vnode -u 0 -f $SWAP || /bin/sh /bin/chflags nodump $SWAP /sbin/swapctl -a $SWAP And /etc/rc.shutdown.local cleans it up: /sbin/swapctl -d /dev/md0 /sbin/mdconfig -d -u 0 Suggestions for improvement? > > configure it as a > > memory disk, and enable it with swapctl. > > In 10.x, this can be done in /etc/fstab. This is on (or for) 10.0, how exactly does it work, which options are involved? Note that the above method has been "invented" for the use with SSDs in FreeBSD 8 and 9, so possibly it's easier to do something similar in FreeBSD 10... -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20140723032002.2a34a6b1.freebsd>