On 07/29/2016 06:00 AM, Mel Gorman wrote:

On Fri, Jul 29, 2016 at 10:13:40AM +1000, Dave Chinner wrote:

quoted

On Thu, Jul 28, 2016 at 11:25:13AM +0100, Mel Gorman wrote:

quoted

On Thu, Jul 28, 2016 at 03:49:47PM +1000, Dave Chinner wrote:

quoted

Seems you're all missing the obvious.

Add a tracepoint for a shrinker callback that includes a "name"
field, have the shrinker callback fill it out appropriately. e.g
in the superblock shrinker:

	trace_shrinker_callback(shrinker, shrink_control, sb->s_type->name);

That misses capturing the latency of the call unless there is a begin/end
tracepoint.

Sure, but I didn't see that in the email talking about how to add a
name. Even if it is a requirement, it's not necessary as we've
already got shrinker runtime measurements from the
trace_mm_shrink_slab_start and trace_mm_shrink_slab_end trace
points. With the above callback event, shrinker call runtime is
simply the time between the calls to the same shrinker within
mm_shrink_slab start/end trace points.

Fair point. It's not that hard to correlate them.

True but the scan_objects callback is only called if we have >batch_size objects.

It's possible to accumulate quite some time without calling the callback and being able to obtain 
the s_type->name.   So this time all gets associated with just super_cache_scan.

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