Re: [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick
From: Anna-Maria Gleixner
Date: Fri Jul 13 2018 - 08:01:56 EST
Hi Haris,
On Thu, 28 Jun 2018, Haris Okanovic wrote:
> Collect expired timers in interrupt context to avoid overhead of waking
> ktimersoftd on every scheduler tick.
>
> This is implemented by storing lists of expired timers in the timer_base
> struct, which is updated by the interrupt routing on each tick in
> run_local_timers(). TIMER softirq (ktimersoftd) is then raised only when
> one or more expired timers are collected.
>
> Performance impact on a 2core Intel Atom E3825 system:
> * reduction in small latency spikes measured by cyclictest
> * ~30% fewer context-switches measured by perf
> * run_local_timers() execution time increases by 0.2 measured by TSC
>
I'm also working on timer improvements at the moment. When I fixed all
my bugs in my implementation (there is a last horrible one), I'm very
interested in integrating your patches into my testing to be able to
give you a tested-by.
Thanks,
Anna-Maria