Messages in this thread | | | Date | Thu, 11 May 2006 12:19:20 -0500 | From | Nathan Lynch <> | Subject | Re: [PATCH 0/10] bulk cpu removal support |
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Ashok Raj wrote: > On Wed, May 10, 2006 at 11:06:06PM -0700, Andrew Morton wrote: > Hi Andrew, > > > Shaohua Li <shaohua.li@intel.com> wrote: > > > > > > CPU hotremove will migrate tasks and redirect interrupts off dead cpu. > > > > This seems an awful lot of code for something which happens so infrequently. > > > > How big is the problem you're fixing here, and what are the > > user-observeable effects of these changes? > > This is useful when say a NUMA node is being removed. With new multi-core > CPUs comming up, considering a 2 core with HT, we could have up to 4 logical > per socket. On NUMA node with 4 sockets, a node removal will mean we > do 16 single cpu offlines. Each time the process and interrupts could > end up on a CPU that might be removed just immediatly.
But offlining all the cpus in a node is already something that just works. If the user is all that concerned about not thrashing the tasks running on that node, they would have a workload manager that migrates the tasks off the node before shooting down cpus. Similar argument applies to interrupt affinity.
I really haven't seen a compelling argument for why this is needed, just a bunch of handwaving so far, sorry.
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