Per process DSCR + somefixes
aik at au1.ibm.com
Wed Feb 2 17:22:59 EST 2011
This is reworked http://patchwork.ozlabs.org/patch/71489/
Originally there were 4 questions left:
It is left as is.
2. Out of band method of changing the DSCR:
Introduced new /sys/devices/system/cpu/dscr_default and "dscr_inherit"
flag for a thread's DSCR which is used in copy_thread to decide whether
to inherit a DSCR value or not.
The "inherit" flag is set when:
- DSCR has been explicitly changed by writing DSCR;
- a parent process has this flag set;
- dscr_default is not 0 at the moment of fork().
In all other cases DSCR remains zero.
3. improve context switch speed.
4. About disabling the feature when there is "no stinking DSCR".
The calls likes:
ensure that DSCR is not accessed on systems which do not support it.
Tested on power5, power6, power7.
IBM OzLabs, LTC Team
e-mail/sametime: aik at au1.ibm.com
notes: Alexey Kardashevskiy/Australia/IBM
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