Messages in this thread | | | Date | Wed, 04 Jun 2008 05:58:29 -0400 | From | Mark Hounschell <> | Subject | Re: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses) |
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Nick Piggin wrote: > On Tuesday 03 June 2008 08:45, Peter Zijlstra wrote: >> On Tue, 2008-06-03 at 00:35 +0200, Ingo Oeser wrote: >>> Hi Paul, >>> >>> in short: NAK! >>> >>> On Monday 02 June 2008, Paul Jackson wrote: >>>> (Aside to the RealTime folks -- is there a 'realtime' >>>> email list which I should include in this discussion?) >>>> >>>> The kernel has a "isolcpus=" kernel boot time parameter. This >>>> parameter isolates CPUs from scheduler load balancing, minimizing the >>>> impact of scheduler latencies on realtime tasks running on those CPUs. >>> I used it to mask out a defect CPU on a 8-CPU node of a >>> HPC-cluster at a customer site, until the $BIG_VENDOR >>> sent a replacement. And to prove $BIG_VENDOR, that we actually >>> have a problem on THAT CPU. >>> >>> So I would really like to keep this fault isolation capability. >>> I made my customer happy with that. >>> >>> I wish Linux had more such "mask out bad hardware" features >>> to faciliate fault isolation and boot and runtime. >> Yeah - except that its not meant to be used as such - it will still >> brings the cpu up, and it is still usable for the OS. >> >> So sorry, your abuse doesn't make for a case to keep this abomination. > > How come it is an abonination? It is an easy way to do what it does, > and it's actually not a bad thing for some uses not to have to use > cpusets. > > Given that it's all __init code anyway, is there a real reason _to_ > remove it?
IMHO,
What is an abonination, is that cpusets are equired for this type of isolation to begin with, even on a 2 processor machine.
I would like the option to stay and be extended like Max originally proposed. If cpusets/hotplug are configured isolation would be obtained using them. If not then isolcpus could be used to get the same isolation.
From a user land point of view, I just want an easy way to fully isolate a particular cpu. Even a new syscall or extension to sched_setaffinity would make me happy. Cpusets and hotplug don't.
Again this is just MHO.
Regards Mark
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