* Andrew Morton <akpm@linux-foundation.org> wrote:
Claiming all user-available CPU time from user-space is already
possible: use SCHED_FIFO - the only question are remaining latencies
in the final 0.01% of CPU time you cannot claim via SCHED_FIFO.
( Btw., this scheduling feature was implemented in Linux well before
raw IO block devices were implemented, so i'm not sure what you
mean by 'freaking out'. )
What we are objecting to are these easy isolation side-hacks for the
remaining 0.01% that fail to address the real problem: the
latencies. Those latencies can hurt not just isolated apps but _non
isolated_ (and latency critical) apps too, and what we insist on is
getting the proper fixes, not just ugly workarounds that side-step
the problem.
( a secondary objection is the extension and extra layering
of something that could be done within existing APIs/ABIs too. We
want to minimize the configuration space. )
Precisely. This feature as proposed here hinders the correct
solution being implemented - and hence hurts long term
maintainability and hence is a no-merge right now. [It also weakens
the pressure to fix latencies for a much wider set of applications,
hence hurts the quality of Linux in the long run. (i.e. is a net
step backwards)]
Ingo
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