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| =System Caches=
| | {{Moved To Userbase}} |
| There are several caches for KDE data that are created when they are
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| first needed. Especially in setups where there is no persistent
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| HOME directory available or where NFS is used, the creation of the
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| caches can considerably increase the time it takes after login
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| until the Desktop session becomes usable.
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| This page is intended to give an overview of the existing caches and
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| provide tips on how to improve the caching behavior in your setup.
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| == General ==
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| Caches are placed by default into /var/tmp/kdecache-<username> and
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| a symlink pointing to that cache is placed in the KDEHOME directory
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| under cache-<hostname>. You can move that loctation by modifing the
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| [http://techbase.kde.org/KDE_System_Administration/Environment_Variables#KDEVARTMP KDEVARTMP]
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| environment variable.
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| All caches are memory mapped at startup to improve perfomance when
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| their contents are accessed. Each user needs is own cache with write
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| access to it.
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| === KSycoca ===
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| KSycoca is the "KDE SYstem COnfiguration CAche". It contains a binary
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| representation of the various .desktop files that provide information
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| about installed software and services and which default applications
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| should be used. (See [http://techbase.kde.org/KDE_System_Administration/XDG_Filesystem_Hierarchy
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| XDG_Filesystem_Hierarchy] for more information about desktop files.
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| Due to the potential number of desktop files and locations where
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| the desktop files can be stored rebuilding the KSycoca cache can take
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| a while, especially if your /usr directory is mounted on a Network
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| File System.
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| To check how long this takes on your system you can trigger a full rebuild
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| of the KSycoca database by executing:
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| kbuildsycoca4 --noincremental
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| === Icon Cache ===
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| The icon cache is used to store the decompressed pixmaps of used icons so
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| that they can be shared in multiple applications.
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| Although the icon cache does not considerably affect the time it takes
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| for the KDE Desktop to become available after login, it can create
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| a bad user experience when after a long login the users finally
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| opens an icon intensive application like the Start Menu as this
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| will again result in a large number of system calls to find the
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| best size of an icon in various locations.
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| === Plasma Cache ===
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| The plasma cache is the largest of the caches when you use Plasma
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| Desktop. But again this contains mostly decompressed Pixmaps of images
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| (like your wallpaper). As those pixmaps are transferred while they
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| are still compressed, persisting this cache on an NFS might even negatively
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| affect your performance.
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| === Other Caches ===
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| There are some other caches used by various applications but those are
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| mostly small and do not considerably affect the performance of the
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| Desktop session as a whole.
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| == Using prepared caches to increase performance ==
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| To avoid rebuilding the KSycoca and the Icon cache for each new user
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| you can create an up to date cache for your system and copy it on
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| startup into the users cache directory. This will significantly reduce
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| the number of "open" system calls excuted when starting a KDE
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| Desktop session.
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| In a deployment where the start of a desktop session took ~80 seconds
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| the startup time could be reduced by this measure to ~50 seconds.
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| The downside is that you have to manually update this cache after installing
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| or updating new software.
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| To create your caches:
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| * Log in with a fresh user. Open the start menu, maybe start an often used application like dolphin.
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| * Copy the files: icon-cache.kcache kdesycoca4 and kdesycoca4stamp from the users cache directory to a globally readable folder e.g.: /var/cache/kde
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| * Set an environment variable pointing to the cache. You can do this with:
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| echo "export KDE_PREP_CACHE=/var/cache/kde" > /usr/share/env/global-cache.sh
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| (This will be sourced by the startkde script)
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| Then apply the following patch to your startkde script (or do something similar in there):
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| --- startkde.orig 2012-11-28 10:38:50.000000000 +0000
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| +++ startkde 2012-11-29 10:50:05.000000000 +0000
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| @@ -255,6 +255,28 @@
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| fi
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| done
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|
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| +# Check if there are prepared caches and copy them to the
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| +# users location if he does not have any caches.
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| +# You can use this to speed up initial KDE startup times.
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| +if test -n "$KDE_PREP_CACHE"; then
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| + cache_config_path=$(kde4-config --path cache)
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| + if test -f "${KDE_PREP_CACHE}/icon-cache.kcache"; then
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| + cp -u --preserve=timestamps "${KDE_PREP_CACHE}/icon-cache.kcache" "${cache_config_path}/icon-cache.kcache"
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| + touch ${cache_config_path}/global_icon_cache_used
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| + fi
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| + if test -f "${KDE_PREP_CACHE}/ksycoca4" -a "${KDE_PREP_CACHE}/ksycoca4stamp"; then
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| + if test -n "${KDESYCOCA}"; then
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| + cp -u --preserve=timestamps "${KDE_PREP_CACHE}/ksycoca4" "${KDESYCOCA}"
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| + cp -u --preserve=timestamps "${KDE_PREP_CACHE}/ksycoca4stamp" "${KDESYCOCA}stamp"
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| + touch ${cache_config_path}/global_sycoca_used
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| + else
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| + cp -u --preserve=timestamps "${KDE_PREP_CACHE}/ksycoca4" "${cache_config_path}"
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| + cp -u --preserve=timestamps "${KDE_PREP_CACHE}/ksycoca4stamp" "${cache_config_path}"
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| + touch ${cache_config_path}/global_sycoca_used
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| + fi
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| + fi
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| +fi
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| +
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| # In case of dcop sockets left by a previous session, cleanup
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| #dcopserver_shutdown
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