Bug 10167

Summary: Code generator should not generate 0-length padding
Product: XCB Reporter: Ian Osgood <iano>
Component: LibraryAssignee: Jamey Sharp <jamey>
Status: RESOLVED WONTFIX QA Contact:
Severity: enhancement    
Priority: medium CC: jamey, josh
Version: 1.0   
Hardware: All   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Ian Osgood 2007-03-02 22:23:58 UTC 
One of XCB's performance bottlenecks is the memcpy inside of write_block.  The code generator often will include zero-length padding in the case where no padding is required, due to not knowing the pre-aligned sizes of the relevant types.  We should make the generator smart about this. Jamey did some preliminary measurements; it would be a measurable performance gain.  (cf. mailing list)
Comment 1 Jamey Sharp 2007-03-03 14:30:36 UTC 
I provided measurements of the effect of fixing both this bug and #6686 in the message "best-case X no-op performance measurement":
http://lists.freedesktop.org/archives/xcb/2006-June/001697.html
Comment 2 Daniel Stone 2019-02-16 13:04:05 UTC 
If this is only for micro-optimisation of request-heavy workloads, there's no great need to do that. But if anyone's really motivated, hey, this can remain for historical interest.

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