Date: Mon, 11 Dec 2017 18:27:35 -0700 From: Gary Aitken <freebsd@dreamchaser.org> To: Matthew Seaman <matthew@FreeBSD.org>, freebsd-questions@freebsd.org Subject: Re: Subject: Thunderbird causing system crash, need guidance Message-ID: <2ae72a98-9584-aee2-bb41-31dbc31250f8@dreamchaser.org> In-Reply-To: <460ae512-89b6-d09f-b567-fefff373b087@FreeBSD.org> References: <201712110045.vBB0jCTQ078476@nightmare.dreamchaser.org> <CA%2BtpaK0sG31TckxL8orNmAD0ZXSz7rJzEotjsCEtASw9u2COZg@mail.gmail.com> <38e2ef70-fa1b-25bf-4447-752006418d0a@dreamchaser.org> <460ae512-89b6-d09f-b567-fefff373b087@FreeBSD.org>
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On 12/11/17 00:56, Matthew Seaman wrote: > On 11/12/2017 04:56, Gary Aitken wrote: > >>>> md99 none swap sw,file=/usr/swap/swap,late > 0 0 > >>> Your swap configuration is also mostly likely silly. If you need >>> more performance, that's not the way to do it. > >> Can you explain or point me to an explanation for this comment? It >> looks to me like what's shown in the EXAMPLES section of "man fstab". > > You're swapping to a file-backed memory device, which is not the best > choice for performance. The best choice is to swap to raw partitions on > your hard drives. Having several disks with a swap partition on each > can help, as it allows you to spread the IO load over several devices, > but that's a marginal gain and not necessary in general. > > The reasoning being that you're involving all of the kernel machinery to > support filesystem IO for what is meant to be the very low-level and > simplified operation of paging memory in and out of swap. > > Yes, you can create a file-backed swap area, but just because you can > doesn't mean you should. Creating a file-backed swap is useful in > special cases, like you're working on that part of the kernel and need > to test adding or removing swap devices, or you're trying to cope with > some exceptional process that is really far too large for your system to > handle. > > Ideally nowadays you should have enough RAM to contain all of your > active processes without needing to swap, so the whole point should > really be moot. Many thanks for the clarification. Gary
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