Date: Fri, 4 Dec 1998 10:39:18 -0600 (CST) From: Kevin Day <toasty@home.dragondata.com> To: luigi@labinfo.iet.unipi.it (Luigi Rizzo) Cc: hackers@FreeBSD.ORG Subject: Re: Nonblocking page fetching Message-ID: <199812041639.KAA28408@home.dragondata.com> In-Reply-To: <199812041308.OAA08387@labinfo.iet.unipi.it> from Luigi Rizzo at "Dec 4, 1998 2: 8:30 pm"
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> > > > This has some obvious disadvantages, but it stopped my movie player from > > > > sitting in vmwait when it could be doing other things. > > > > > > is it so bad ? The forked process should consume very little memory > ... > > Well, I may be wrong, but I assumed that the CPU involved in just having a > > kernel bring pages in on it's own would be less. Is there anything that > > could be saved by putting this in the kernel? > > let's see... you fork a process once so that does not count. Every > bunch of prefetch requires an IPC, and every page causes a context > switch (or two ?) following the page fault. This is what you can save. > I cannot quantify times for all the above activities, maybe someone > else has some numbers. Ok, maybe I'm making a bigger deal of it than it is. > > >>> One final note... Does anyone know what effect turning off the bzero on new > >>> pages would be? Security is not an issue in this system, as it's not > > i think a lot of software will break. Doesn't that break the golden rule of never assuming the contents of new memory? > > >> again how bad is it ? bzero is generally done in the idle loop if i am > ... > > We are at 100% cpu constantly. When I'm not drawing, i'm prerendering frames > > ok, so think this differently: bzero'ing occurs at memory speed which > could be around 200-400MB/s in your case, or 10-20us/page. > Without giving away too much information, we're using a unified memory system, bandwidth usage is of extreme importance. Kevin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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