On Wed, Feb 24, 2021 at 01:18:10PM -0800, Darrick J. Wong wrote:

On Tue, Feb 23, 2021 at 02:34:42PM +1100, Dave Chinner wrote:

quoted

From: Dave Chinner <redacted>

A hang with tasks stuck on the CIL hard throttle was reported and
largely diagnosed by Donald Buczek, who discovered that it was a
result of the CIL context space usage decrementing in committed
transactions once the hard throttle limit had been hit and processes
were already blocked.  This resulted in the CIL push not waking up
those waiters because the CIL context was no longer over the hard
throttle limit.

The surprising aspect of this was the CIL space usage going
backwards regularly enough to trigger this situation. Assumptions
had been made in design that the relogging process would only
increase the size of the objects in the CIL, and so that space would
only increase.

This change and commit message fixes the issue and documents the
result of an audit of the triggers that can cause the CIL space to
go backwards, how large the backwards steps tend to be, the
frequency in which they occur, and what the impact on the CIL
accounting code is.

....

Does this whole series fix the Donald's problem?

No, just this patch is needed to fix that problem.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com