HotSpots
(Created page with "= Kernel Hotspots and Problems = Much of this dicussion came about during OLS 2005 and the PARISC Mini-bof we held on Thursday July 21st, 2005. == Problem the first - More C...") |
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Possible solutions include: | Possible solutions include: | ||
| − | + | * Linux kernel crash dump (Dump crash data to the network). | |
| − | + | * Kexec (Launch second kernel to debug incore data). | |
| − | + | * Netdump? | |
== Problem the second - Floating Point Registers - == | == Problem the second - Floating Point Registers - == | ||
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to limit the use of floating point registers. | to limit the use of floating point registers. | ||
| − | + | Update: With the 3.x kernels we switched to gcc-4.x and instruct it to not use floating point registers any longer. Problem doesn't exist any longer. | |
| − | registers. | + | |
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Latest revision as of 17:41, 5 February 2014
[edit] Kernel Hotspots and Problems
Much of this dicussion came about during OLS 2005 and the PARISC Mini-bof we held on Thursday July 21st, 2005.
[edit] Problem the first - More Crash Info -
When the kernel fails we need more information to debug the problem. Possible solutions include:
- Linux kernel crash dump (Dump crash data to the network).
- Kexec (Launch second kernel to debug incore data).
- Netdump?
[edit] Problem the second - Floating Point Registers -
We have re-enabled floating pointer registers around the 2.6.9 era, and this introduced a bug in our code. The bug was rather subtle and fixed by James Bottomley. The issue was that our _switch_to and _switch_to_ret was not saving the callee saves floating point registers. The situation arose that one of the floating point registers was getting trashed in the pa_memcpy code which usually meant something died with an invalid copy.
There are still some stability issues and crashes in pa_memcpy. It seems the Joel Soete has had some limited success using GCC 4.0 to limit the use of floating point registers.
Update: With the 3.x kernels we switched to gcc-4.x and instruct it to not use floating point registers any longer. Problem doesn't exist any longer.
