[Webkit-unassigned] [Bug 240006] New: [GTK][WPE] Expensive atomic operations, overabundant semaphore signaling in GPUProcess streaming IPC

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=240006

            Bug ID: 240006
           Summary: [GTK][WPE] Expensive atomic operations, overabundant
                    semaphore signaling in GPUProcess streaming IPC
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: New Bugs
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: zan at falconsigh.net
                CC: kkinnunen at apple.com
            Blocks: 238593

As messages traveling on the streaming IPC channel between WebProcess and GPUProcess increase in count (e.g. due to the complexity of the scene), atomic operations handling loading and exchanging client and server offset values start taking considerable chunk of CPU time. Additionally, there's aggressive semaphore signalling done from the WebProcess when all the data is flushed for the GPUProcess to pick up and process, to the point where the write syscall becomes visible on the profiling output.

This has only been observed on Linux. Atomic ops might affect Cocoa ports as well, but signalling of the eventfd-based semaphore is specific to Linux, at least in how it evolves into a time waste.

For now this will just try and log the problem, no solution has been devised yet.


Referenced Bugs:

https://bugs.webkit.org/show_bug.cgi?id=238593
[Bug 238593] [GTK][WPE] GPUProcess support
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