Date: Mon, 27 Dec 1999 16:26:59 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Proposed patch to fix VN device (again) Message-ID: <199912280026.QAA34572@apollo.backplane.com> References: <7427.946340596@critter.freebsd.dk>
next in thread | previous in thread | raw e-mail | index | archive | help
:
:In message <199912280012.QAA34430@apollo.backplane.com>, Matthew Dillon writes:
:
:> Sigh. Ok, I've fixed the VN device. Again. It looks like the removal of
:> /dev/drum removed a little too much. We need the device infrastructure
:> to support the VN device's use of swap backing store.
:>
:> This patch below is a commit candidate. It could use a review, then I'll
:> commit it.
:
:Could you please explain why you need this ?
:
:--
:Poul-Henning Kamp FreeBSD coreteam member
:phk@FreeBSD.ORG "Real hackers run -current on their laptop."
:FreeBSD -- It will take a long time before progress goes too far!
VN calls vm_pager_strategy() which collects I/O in filesystem buffers
(bp)'s in order to cluster the I/O, and you cannot initiate I/O on
filesystem buffers without a valid b_dev.
So, the jist of the problem is that in order to get reasonable performance
out of the thing (i.e. not issue 4K I/O's to the disk), we have to use
filesystem buffers which means the bp must be properly initialized.
-Matt
Matthew Dillon
<dillon@backplane.com>
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199912280026.QAA34572>