[Kde-hardware-devel] Hotplug dataengine performance

[Jacopo De Simoi]

Ping
 Any comments on this? is it good to commit?

On Friday 18 December 2009 12:04:57 Jacopo De Simoi wrote:
> Dear Hardware-devels, 
>   even after the caching work by ervin & aseigo I was experiencing serious performance issues with the hotplug dataengine;
> and serious meant that each device takes ~500ms to show up 
> 
> I finally tracked it down: it turned out it was spending ~50ms on each check for the "ignored" property; 
> the problem is the implementation of HalVolume::isIgnored(); the first two lines read as follows:
> 
> HalDevice lock("/org/freedesktop/Hal/devices/computer");
> bool isLocked = lock.property("info.named_locks.Global.org.freedesktop.Hal.Device.Storage.locked").toBool();
> 
> hence for each check of "ignored" we /create/ a new device for computer (~25ms)
> and then we check the property (~25ms), obviously hitting a cache miss since the device has just been created :-/
> 
> Since pretty much every predicate checks for ignore and you easily get to the ~500ms per device that I was experiencing.
> HalVolume doesn't have a d-ptr, so I could only come out with the following patch, which is ugly, but does the job pretty well
> 
> -    HalDevice lock("/org/freedesktop/Hal/devices/computer");
> +    static HalDevice lock("/org/freedesktop/Hal/devices/computer");
> 
> now I'm down to ~50ms per device \o/
> Please let me know if there's a better way to implement the patch.
> Regards
> 
>    --J
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