Re: Optimum page file size for 1 GB?

Previously Alexander Grigoriev <alegr@xxxxxxxxxxxxx> wrote:

"Arno Wagner" <me@xxxxxxxxxxx> wrote in message
news:56ga6eF289fdtU2@xxxxxxxxxxxxxxxxxxxxx
Previously Alexander Grigoriev <alegr@xxxxxxxxxxxxx> wrote:
When kernel bugcheck occurs, it's not a good idea to go to filesystem and
create a file. After all, your filesystem driver may be screwed all over
by
a faulty driver that caused the crash. If you call it, it might as well
say
goodbye to the whole partition.

Ah, you are talking about kernel crashes!

You said 'Under UNIX the kernel dumps to file". This usually happens during
kernel panic (AKA kernel crash).

Not at all. Under UNIX the kernel dumps the memory of a crashed
application to file. Dumping the kernel memory is such a bad
idea that I did not even consider you were talking about that.

If an application blows chunks, it's usually called coredump.

And it is performed by the kernel...

By the way, in Windows you can do a similar thing
and save an application dump for postmortem debugging. This is used by ISV
to analyse customer site crashes.


In Windows, crash dump is written by a special part of the disk driver,
which is normally not even mapped to kernel space, to avoid its
corruption.

This sounds very much like wishful thinking to me. Could explain some
of the disk corruption people have experienced after windows crashes.
The right way to do this is to not touch the disk at all after akernel
problem.

Especially creating a file for kernel dump, like you say UNIX does.

Let me repeat: There are no kernel dumps under UNIX. The only thing
I know of is the Linux kernel debugger were you can dump to serial
line, i.e. a different system. Accessing the disk after a kernel problem
is not a sane thing to do.

I've seen my share windows crashes. Some happened when I was
debugging my own driver. Lost some files on a FAT32 partition
because of that. Other happened because of a faulty video
driver. Other happened because RAM sticks went sour (Crucial, if
you're curious). Other happened because MB went south (a particular
bit on memory bus was unstable _only_ when disk I/O was
active). Never had NTFS corruption because of that, which is
amazing. On the other hand, I've never run any Norton/Symantec
crapware. That might explain.

You can allow remote debugging over a serial line, e.g..

If Windows is run with /crashdebug boot option, it will try to
connect to a remote debugger (which can be serial, Firewire, or, in
Vista, over Ethernet) in case of bugcheck. If /debug option is used,
the debugger will be always active, it will do that even in case of
application crash, and DivX will go on a breakpoint, too. This
allows debugging applications in headless configuration, and
debugging system services.

Ans that is how it should be done.


Position to where to write the dump is known beforehand, during pagefile
initialization. When crash dump starts, bugcheck handler maps the dump
writer which then does the job.

And why in this universe would anybody want a windows system crash-dump
on their disk? Is there anything at all you can do with it?


Postmortem crash analysis and reporting implemented in XP allowed MS to
identify many problematic in-house and 3rd party drivers. 3rd party driver
crashes are reported to the vendors. This is better than users suffering in
silence, pulling hair from all places.

Well, this has some uses for developers, but for ordinary users it
sounds a) mostly useless b) dangerous because there are disk accesses
after the kernel (and hence possibly the disk and controller) is in
an undefined state. This shoul be turned off as default.

Arno



.

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