Date: Mon, 21 Jan 2002 02:02:17 -0800 (PST) From: Raman Ng <ramanng@yahoo.com> To: Terry Lambert <tlambert2@mindspring.com>, raman@hello.to Cc: stable@freebsd.org, current@freebsd.org Subject: Re: Extended paging bug in Athlon affect FreeBSD? Message-ID: <20020121100217.81572.qmail@web14002.mail.yahoo.com> In-Reply-To: <3C4BCB4F.60F1D4FC@mindspring.com>
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> I am well aware of this bug. > > It does not affect FreeBSD, which only uses 4M pages > for > the first 4M of the kernel itself. > > I've worked on code that enables 4M pages on other > memory > used in FreeBSD, that had this problem, but only if > you > were really stupid in your allocation mechanism. > > There's a workaround for this problem which is > fairly > trivial to implement in software, and should > probably be > done when 4M pages are enabled, if you are using an > Athlon, > and are adding 4M pages. The problem didn't bite my > own > application, since I knew about it and used the TLBs > in a > very specific way to get around the problem, but I'm > told > that after I left the company, someone went in and > used > them a different way, not knowing about the problem > or the > workaround, and broke things. This resulted in > about a > 14% performance loss. > > If you are doing heavy networking on a machine with > a lot > of memory, it's reasonable to move your mbufs into > 4M pages, > which nets you a 4-14% improvement (depending on > whether or > not you also change your allocator: 14% if you do). > If you > do that, knowing how to work around the problem nets > you a > pretty big win in overall performance, for about > 6-10 more > machine instructions at startup time. 8-). > > In any case, this will not be a problem for FreeBSD, > and is > only a problem for Linux because of the strange way > they > initialize things. > > -- Terry Glad to know FreeBSD is not affected. Thanks a lot. Cheers, Raman __________________________________________________ Do You Yahoo!? Send FREE video emails in Yahoo! Mail! http://promo.yahoo.com/videomail/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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