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E10K: Debugging Drain Failures
=======================================================
:Title:        E10K: Debugging Drain Failures
:Author:       Douglas O'Leary <dkoleary@olearycomputers.com>
:Description:  E10K: Debugging Drain Failures
:Date created: 08/1999
:Date updated: 09/1999
:Disclaimer:   Standard: Use the information that follows at your own risk.  If you screw up a system, don't blame it on me...

1.  Enable the kernel variable dr_mem_debug by setting its value to -1 using 
    either adb or setting the value in /etc/system and reboot::

        # adb -kw 
        physmem 13af5d 
        dr_mem_debug/W0x1 
        dr_mem_debug: 0x0 = 0x1 
        $q

2.  Capture the console output from a failed DR drain session. The failed 
    address will be readily apparent, the message will be something to the 
    effect:

        hold_pfns: page not held: <some address>

3.  In an adb session, enter the following command::

        <page address from step 2>$<page

4.  Look for the field p_selock. If the value in this field is 1, the 
    problem is possibly related to swap.
5.  If there is a value in the p_vnode field, then enter the following::

        <vnode address>$<vnode

    Look for the vop field, this tells us which virtual operation is in 
    progress.

6.  If the value in p_selock is an address, then we need to adjust the value 
    of  this address by subtracting 8 from the high order bit. For example, 
    if the p_selock field = c0000000, then the value we need for the next 
    step is 40000000. This is a thread address. To check this, enter the 
    following command::

        <thread address>$<thread

7.  Look for the field called procp and get that address. Enter the 
    following::

        <proc address>$<proc2u

8.  Search through the screen output for the psargs field. This will 
    indicate the process that is holding the lock.

If this is a 3rd party vendor, we need to know who. In any case, mail the 
screen output to us and we will look further at it.

Notes on adb: Be careful of the columns. Things don't always align