On Fri, Sep 30, 2016 at 2:35 PM, Sebastian Kügler <se...@kde.org> wrote: > Hi, > > On Tuesday, September 27, 2016 4:52:22 PM UTC Marco Martin wrote: >> as there is being some work in plugin caching right now, to see if /what we >> can save at startup time would be nice if different people on different >> systems do some tests. >> on his system, by indexing plugins Sebas saves about 2-300 milliseconds. How >> did you test that, so that we see wether we can reproduce it on different >> systems, (may well be that on some kinds of hardware it's worth it, not on >> some other) > > My measuring was done as follows: > - I instrumented Plasma::PluginLoader and recorded all calls to > KPluginLoader::findPackage(...) > - I put these queries into an autotest, and instrumented that with timers that > measure the time spent in KPluginLoader::findPlugins(...), with and without > cache. > > So my tests are a little more synthetic. My code is in kcoreaddons[sebas/ > pluginindexer2], the index is generated with > > $ kpluginindexer -u > > Results on my fast system (core i7 + ssd) is that for Plasma startup, the > indexed code runs about 200ms faster (out of a total ~700). That's not a lot > of gain, IMO, and I'm unsure if it justifies the complexity added by > maintaining an index. > > I haven't done any measurements on cold caches. > >> I did a similar test on kpackage plugin indexes, that's how all plasmoids >> get loaded, so it's quite a lot of them. > > Nice, I suppose KPackages are a little different to plugins, since there's > more overhead reading, the package metadata is stored as .desktop file, which > means more conversion costs compared to the binary json that's in the plugin > binaries. Aleix has recently been looking into converting it to json, but that > would only save the .desktop to json part, binary json is still much quicker > to read (the format is pretty close to Qt's internal representation in memory, > deserialization is almost entirely I/O-bound.
It's not only about loading from json. Keep in mind that even adding a cache we'll be loading each metadata.desktop a number of times either way (both using KConfig parsing and KCoreAddons' DesktopFileParser). My suggestion is to first get the type system right in plasma-framework then we look into enforcing caches. I'm especially afraid of this one as it will require quite a lot of work from the packagers. Furthermore, it would also be really interesting to look into reducing plugin look-ups altogether, I'm almost sure that plugins are listed several times on every boot. Aleix
