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Re: Coalesced Updates & QuartzDebug

Looks like Eric pointed you to it already. We're hoping to document the feature in an upcoming Technical Q&A, but I'd though I'd add some information that may be useful:

The three options are :
1) Disable Beam Synchronization
This disables all beam syncing in the system, including the Coalesced Update feature. So you will see visual tearing, but increased performance because your drawing calls will no longer block waiting for the previous flush to complete. Use this mode for benchmark testing to see what the total throughput of your code is (disregarding the the display flushing). There is currently no way to disable just the Coalesced Update feature only.

2) Automatic Beam Synchronization
This is the default for Tiger. In this mode, beam syncing is enabled for window geometry changes (also true in Panther) and the Coalesced Update feature is also enabled. The latter is new to Tiger and will result in the window server coalescing display updates across applications into a single update to the display waiting for a vertical blank of the display. This is tied to the display refresh rate and is also applicable to LCD monitors (which really update at 60Hz). This results in better system performance, but can have side- effects to applications that attempt to flush faster than the refresh of the display. Note that only mach-o applications linked on Tiger will initiate coalesced updates. CFM and apps built pre-Tiger will not initiate a coalesced update, but if another application has initiated a coalesced update for a vbl, then the original app's update will also be coalesced.

3) Force Beam Synchronization
This will force coalescing of updates across all applications. Developers can use this to check the performance impact of the feature without waiting to link their application on Tiger. Right now, the first time the app tries to flush faster than the display refresh rate or ends up spending more that 50% of it's time waiting for the vbl will have a message logged to /var/log/windowserver.log. The message is of the format : "Application "SuchAndSuch" is being throttled by update coalescing." This message will only be output once per application. Developers should monitor this log to check to see if their application is being impacted by coalesced updates or not.

haroon

On May 19, 2005, at 12:22 PM, Nicholas Jackiw wrote:

Loosely related to the ongoing discussions about Tiger buffer flushing, in the various Tiger seed release notes and now in the 10.4 Developer Release Notes, the discussion about the perils of coalesced update includes the note:

"The QuartzDebug utility in /Developer/Applications/Performance Tools has new options in Mac OS X 10.4 that allow you to force coalesced updates on for all applications. You will find this to be useful when determining whether your existing application might have performance problems when it is relinked on 10.4 or later."

Does this actually exist, and if so, where in QuartzDebug do I find it? The version that appears to have been installed with my Tiger developer tools--QuartzDebug 2.1.2--doesn't seem to contain any explicit mention of "coalesced updates."

Thanks,
Nick

On May 17, 2005, at 1:06 PM, Eric Schlegel wrote:

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