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This uses msgsnd where possible for signalling other threads within the same core on POWER8 systems, rather than IPIs through the XICS interrupt controller. This includes waking secondary threads to run the guest, the interrupts generated by the virtual XICS, and the interrupts to bring the other threads out of the guest when exiting. Aggregated statistics from debugfs across vcpus for a guest with 32 vcpus, 8 threads/vcore, running on a POWER8, show this before the change: rm_entry: 3387.6ns (228 - 86600, 1008969 samples) rm_exit: 4561.5ns (12 - 3477452, 1009402 samples) rm_intr: 1660.0ns (12 - 553050, 3600051 samples) and this after the change: rm_entry: 3060.1ns (212 - 65138, 953873 samples) rm_exit: 4244.1ns (12 - 9693408, 954331 samples) rm_intr: 1342.3ns (12 - 1104718, 3405326 samples) for a test of booting Fedora 20 big-endian to the login prompt. The time taken for a H_PROD hcall (which is handled in the host kernel) went down from about 35 microseconds to about 16 microseconds with this change. The noinline added to kvmppc_run_core turned out to be necessary for good performance, at least with gcc 4.9.2 as packaged with Fedora 21 and a little-endian POWER8 host. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de> |
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| .. | ||
| boot | ||
| configs | ||
| crypto | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| math-emu | ||
| mm | ||
| net | ||
| oprofile | ||
| perf | ||
| platforms | ||
| sysdev | ||
| xmon | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| relocs_check.pl | ||