[Kde-pim] "Detected inconsistency in local cache"

[Aaron J. Seigo]

On Thursday, September 3, 2015 16.00:20 David Faure wrote:
> This leads to a lot of akonadi activity and notifications, which leads to
> plasma-destop being busy (100% CPU) in the calendar applet, making plasma
> unusable for entire blocks of 10s, making my wife yell at me :-)

... this is why people should be cracking on with Akonadi Next full steam.

Plasma would not be blocked by such an update storm (queries happen in a 
separate thread) and the processing should occur much faster with no resource 
contention[1] since reads do not interact with each other (until whatever 
shared physical media is involved).

... but there are also opportunities here with Akonadi Next's design to 
mitigate this even further. It would be possible to add information to update 
notifications giving some hint as to what changed, so that if the changes are 
not of interest (in the case of Plasma's calendar: because the changes are not 
in the current date range being shown, or don't include data relevant to the 
calendar, ... ) the client would just completely ignore those. Since these 
notifications take ~0.0012ms[2], it's pretty easy to deal with large volumes 
of them, so if the client is dropping them it really doesn't show up in terms 
of overall performance

[1] which is something which I suspect harms performance to some degree in 
current Akonadi as there are a number of single process bottlenecks that must 
be traversed by each client; when multiple clients start trying to respond to 
updates, I would expect that they end up creating latency in the Akonadi 
system for each other as their "simultaneous" requests end up e.g. in command 
queues on the wire.

[2] not a typo; last I benchmarked this part of the system, my laptop was 
pushing and processing somewhere around 800,000 update notifications per 
second between processes. They are essentially "free".

-- 
Aaron Seigo
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