[PATCH] mieq: Provide better adaptability and diagnostics during mieq overflow

[Jeremy Huddleston]

On Oct 16, 2011, at 8:44 AM, Keith Packard wrote:

> On Sat, 15 Oct 2011 23:31:35 -0700, Jeremy Huddleston <jeremyhu at apple.com> wrote:
> 
>> Yes.  This patch was motivated by some server bugs I read through in
>> bugzilla today.  Apparently some DRI drivers can hog the CPU for a
>> while, delaying processing.  In one of the reports, a user reported
>> that setting the queue size to 4096 actually solved the issue for
>> them.
> 
> One might suggest a better plan would be to fix the obvious problem :-)

I agree.  The problem is that the (sometimes) singular backtrace doesn't always point to the problem, and the current log message makes people blame mieq.  I don't think my patch addresses the second point, but it should help the first.

> How much memory does a queue of length 4096 take these days?

Well in the normal case, this will actually *reduce* memory usage since the default size is 128 rather than 512.  Only systems with problems will grow to 4096, and it was reported that the increased queue actually helps (although honestly I don't see why that would be the case).