While modern workloads are increasingly interactive and resource-intensive (e.g., graphical user interfaces, browsers, and multimedia players), current operating systems have not kept up. These operating systems, which evolved from core designs that date to the 1970s and 1980s, provide good support for batch and command-line applications, but their ad hoc attempts to handle interactive workloads are poor. Their best-effort, priority-based schedulers provide no bounds on delays, and their resource managers (e.g., memory managers and disk I/O schedulers) are mostly oblivious to response time requirements. Pressure on any one of these resources can significantly degrade application responsiveness.
We present Redline, a system that brings first-class support for interactive applications to commodity operating systems. Redline works with unaltered applications and standard APIs. It uses lightweight specifications to orchestrate memory and disk I/O management so that they serve the needs of interactive applications. Unlike realtime systems that treat specifications as strict requirements and thus pessimistically limit system utilization, Redline dynamically adapts to recent load, maximizing responsiveness and system utilization. We show that Redline delivers responsiveness to interactive applications even in the face of extreme workloads including fork bombs, memory bombs and bursty, large disk I/O requests, reducing application pauses by up to two orders of magnitude.
> On 12. Aug 2019, at 18:16, Lennart Poettering <mzerqung@0pointer.de> wrote:
>
> On Mo, 12.08.19 09:40, Chris Murphy (lists@colorremedies.com) wrote:
>
>> How to do this automatically? Could there be a mechanism for the
>> system and the requesting application to negotiate resources?
>
> Ideally, GNOME would run all its apps as systemd --user services. We
> could then set DefaultMemoryHigh= globally for the systemd --user
> instance to some percentage value (which is taken relative to the
> physical RAM size). This would then mean every user app individually
> could use — let's say — 75% of the physical RAM size and when it wants
> more it would be penalized during reclaim compared to apps using less.
>
> If GNOME would run all apps as user services we could do various other
> nice things too. For example, it could dynamically assign the fg app
> more CPU/IO weight than the bg apps, if the system is starved of
> both.
I really like the ideas. Why isn’t this done this way anyway?
I don’t have a GNOME desktop at hand right now to investigate how GNOME starts applications and so on but aren’t new processes started by the user — GNOME or not — always children of the user.slice? Is there a difference if I start a GNOME application or a normal process from my shell?
And for the beginning, wouldn’t it be enough to differentiate between user slices and system slice and set DefaultMemoryHigh= in a way to make sure there is always some headroom left for the system?
BK
(… I definitely need to play around with Silverblue to learn what they are doing.)
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