Date: Wed, 23 Mar 2011 07:51:56 -0400 From: John Baldwin <jhb@freebsd.org> To: Ed Maste <emaste@freebsd.org> Cc: "Bjoern A. Zeeb" <bz@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: kernel memory checks on boot vs. boot time Message-ID: <201103230751.56647.jhb@freebsd.org> In-Reply-To: <20110322224554.GA67925@sandvine.com> References: <alpine.BSF.2.00.1103221634241.6104@ai.fobar.qr> <201103221551.14289.jhb@freebsd.org> <20110322224554.GA67925@sandvine.com>
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On Tuesday, March 22, 2011 6:45:54 pm Ed Maste wrote: > On Tue, Mar 22, 2011 at 03:51:13PM -0400, John Baldwin wrote: > > > Do other platforms bother with these sorts of memory tests? If not I'd vote > > to just drop it. I think this mattered more when you didn't have things like > > SMAP (so you had to guess at where memory ended sometimes). Also, modern > > server class x86 machines generally support ECC RAM which will trigger a > > machine check if there is a problem. I doubt that the early checks are > > catching anything even for the non-ECC case. > > In the common case at work we want this off to reduce boot time. The > desire for a tunable though that can add extended memory tests is to be > able to use the FreeBSD startup code as a replacement for memtest86+, > for a couple of reasons: > > - FreeBSD's serial console output is more easily parsed by automated > tools > - Memtest86+ appears to be limited to 64GB of RAM at the moment > - Memtest86+ lacks support for the Tylersburg architecture last I looked The existing memory check is nowhere near the level of what memtest86+ does and relying on that to give you the same testing strength as memtest86+ seems very dubious to me. If you want a real memory tester, I'd be tempted to just write a custom kernel for that, probably still using BIOS routines for I/O similar to the boot loader, etc. You'd also want to install a MC handler before kicking off the test, but you would want to minimize the amount of RAM you used so you could test as much of the RAM as possible. -- John Baldwin
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