Hello, As part of my ongoing work to get perfmon2 (v2.2) merged into the mainline, I recently submitted patches to prepare the i386 and x86_64 kernel infrastructures.
As suggested by Andi Kleen, I have modified the __switch_to() routines for both architectures so that adding perfmon2 PMU switch code will have no impact for tasks that do not use it. This patch modifies the routine to use the TIF flags to check for optional state to save/restore on conetxt switch. As part of the modification both the debug registers and I/O bitmap checks have been replaced by TIF flags (TIF_DEBUG and TIF_IO_BITMAP). With these new flags, only one cacheline per task is touched to check for optional work (instead of one per thing to check). Once we add perfmon (TIF_PERFMON) there will not be any new cacheline touched on the critical path. The patch was submitted to lkml several weeks ago and I can confirm that it is now integrated into mainline kernel as of 2.6.17.7. At least some progress... -- -Stephane _______________________________________________ perfmon mailing list [email protected] http://www.hpl.hp.com/hosted/linux/mail-archives/perfmon/
