Date: Fri, 22 Sep 2000 08:32:02 +0000 (GMT)
From: Terry Lambert <tlambert@primenet.com>
To: peter@netplex.com.au (Peter Wemm)
Cc: sos@freebsd.dk (Soren Schmidt), Stephen.Byan@quantum.com (Stephen Byan), mbendiks@eunet.no ('Marius Bendiksen'), fs@FreeBSD.ORG, sos@FreeBSD.ORG, freeBSD-scsi@FreeBSD.ORG
Subject: Re: disable write caching with softupdates?
Message-ID: <200009220832.BAA09658@usr05.primenet.com>
In-Reply-To: <200009220757.e8M7vtG46023@netplex.com.au> from "Peter Wemm" at Sep 22, 2000 12:57:55 AM
next in thread | previous in thread | raw e-mail | index | archive | help
> > So, having the write cache there definitly is a win. > > It is a win only if you do not value your data. I would gladly turn it off. > How do we do this right now? (ie: completely off) > > > I'll try this on TWO IBM DTLA drives with tags enabled and see what gives.. > > I'm curious to know if tagged queueing compensates for the loss incurred by > disabling write caching. For a multiple application system, the anser is "yes", so long as there are enough applications that the average stall time for a context switch equals or exceeds the latency induced by waiting for the write to complete (standard queueing theory 8-)). For a single user workstation, where there is generall only one or two applications running, the answer would be "no". For you to be able to see this, the appropriate test is probably a "make world" (or a similar large multielement compile) with an argument between "-j 8" and -j 12". Note that you should probably _not_ use a memfs /tmp for this, at the same time, since what you want to stress is the impact on concurrency under a multiprogram load. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200009220832.BAA09658>