[Bug]KNL:Spread MWAIT cache lines over all nodes
Bug #1585850 reported by
XiongZhang
This bug affects 1 person
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
intel |
Fix Released
|
Undecided
|
Unassigned | ||
linux (Ubuntu) |
Fix Released
|
Undecided
|
Tim Gardner | ||
Xenial |
Fix Released
|
Undecided
|
Tim Gardner | ||
Yakkety |
Fix Released
|
Undecided
|
Tim Gardner |
Bug Description
KNL sees severely degraded memory bandwidth on MCDRAM with C-states deeper than C1 and with sub numa clustering enabled. This has been root caused to all idle task's MWAIT cache line placed in node 0. Node 0's CHA goes into degraded mode because the many MWAIT lines overflow an internal hash table.
Fix is to allocate the idle task's task structs on their respective nodes.
The fix patch is merged into linux-next and will be part of v4.7, please back port into 16.04 kernel:
725fc62 kernek/fork.c: allocate idle task for a CPU always on its local node
Changed in linux (Ubuntu Xenial): | |
status: | In Progress → Fix Committed |
Changed in intel: | |
status: | New → Fix Released |
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This change has been made by an automated script, maintained by the Ubuntu Kernel Team.