Messages in this thread | | | Date | Mon, 23 Sep 2013 16:24:59 -0500 | From | Mike Travis <> | Subject | [PATCH 0/7] x86/UV/KDB/NMI: Updates for NMI/KDB handler for SGI UV |
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V3: Reduce number of changes to KGDB/KDB code to simplify special handling of SYSTEM NMI. Remove disable UV NMI function.
V2: Split KDB updates from NMI updates. Broke up the big patch to uv_nmi.c into smaller patches. Updated to the latest linux kernel version.
The current UV NMI handler has not been updated for the changes in the system NMI handler and the perf operations. The UV NMI handler reads an MMR in the UV Hub to check to see if the NMI event was caused by the external 'system NMI' that the operator can initiate on the System Mgmt Controller.
The problem arises when the perf tools are running, causing millions of perf events per second on very large CPU count systems. Previously this was okay because the perf NMI handler ran at a higher priority on the NMI call chain and if the NMI was a perf event, it would stop calling other NMI handlers remaining on the NMI call chain.
Now the system NMI handler calls all the handlers on the NMI call chain including the UV NMI handler. This causes the UV NMI handler to read the MMRs at the same millions per second rate. This can lead to significant performance loss and possible system failures. It also can cause thousands of 'Dazed and Confused' messages being sent to the system console. This effectively makes perf tools unusable on UV systems.
This patch set addresses this problem and allows the perf tools to run on UV without impacting performance and causing system failures.
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