From owner-freebsd-current  Mon Jan 25 17:00:03 1999
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Date: Mon, 25 Jan 1999 16:59:40 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <199901260059.QAA08899@apollo.backplane.com>
To: Sheldon Hearn <axl@iafrica.com>
Cc: Brian Feldman <green@unixhelp.org>,
        Lee Cremeans <lee@st-lcremean.tidalwave.net>, current@FreeBSD.ORG
Subject: Re: IDE DMA works, I'll be a... 
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:On Mon, 25 Jan 1999 19:40:38 EST, Brian Feldman wrote:
:
:> I say this because I am down to ~2.5MB/s on each hard drive, a MB or
:> so decrease; I also seem to be reading (bs=512k) from the CD uncooked
:...
:
:Since I rebuilt world shortly after Matt's VM surgery started, I've also
:noticed this -- lower apparent transfer rates from /dev/zero to disk,
:higher CPU usage during such transfers.
:
:I'm _not_ saying it's Matt's stuff that's done this, it's just that that
:was the stuff I _noticed_ happening in commit mail. I think I saw
:something happening to wd.c recently as well, so I _definitely_ am not
:going on record as laying blame.
:
:Just some confirmation. :-)
:
:Ciao,
:Sheldon.

    Hmm, interesting.  A dd copy doesn't touch on the main of what I did,
    but I do have a (bad) hack in there to handle a case that John brought
    up in regards to the inactive page queue getting overloaded with
    clean meta-data.  It might be interesting to turn that off and see if
    your transfer rates improve.

    You can turn off the hack by commenting out the case that activates
    it:  Add the #if/#endif and split the open brace out from the else, 
    as shown.

    I would like to know if your transfer rate improves or not, and by
    how much.


        /*
         * Figure out what to do with dirty pages when they are encountered.
         * Assume that 1/3 of the pages on the inactive list are clean.  If
         * we think we can reach our target, disable laundering (do not
         * clean any dirty pages).  If we miss the target we will loop back
         * up and do a laundering run.
         */     
        
#if 0
        if (cnt.v_inactive_count / 3 > page_shortage) {
                maxlaunder = 0;
                launder_loop = 0;
        } else 
#endif
	{
                maxlaunder =
                    (cnt.v_inactive_target > max_page_launder) ?
                    max_page_launder : cnt.v_inactive_target;
                launder_loop = 1;
        }


					-Matt
					Matthew Dillon 
					<dillon@backplane.com>


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