mirror of https://github.com/torvalds/linux.git
4708fba19a
The pseries Shared Processor Logical Partition(SPLPAR) machines can retrieve a log of dispatch and preempt events from the hypervisor using data from Disptach Trace Log(DTL) buffer. With this information, user can retrieve when and why each dispatch & preempt has occurred. Added an interface to expose the Virtual Processor Area(VPA) DTL counters via perf. The following events are available and exposed in sysfs: vpa_dtl/dtl_cede/ - Trace voluntary (OS initiated) virtual processor waits vpa_dtl/dtl_preempt/ - Trace time slice preempts vpa_dtl/dtl_fault/ - Trace virtual partition memory page faults. vpa_dtl/dtl_all/ - Trace all (dtl_cede/dtl_preempt/dtl_fault) Added interface defines supported event list, config fields for the event attributes and their corresponding bit values which are exported via sysfs. User could use the standard perf tool to access perf events exposed via vpa-dtl pmu. The VPA DTL PMU counters do not interrupt on overflow or generate any PMI interrupts. Therefore, the kernel needs to poll the counters, added hrtimer code to do that. The timer interval can be provided by user via sample_period field in nano seconds. There is one hrtimer added per vpa-dtl pmu thread. To ensure there are no other conflicting dtl users (example: debugfs dtl or /proc/powerpc/vcpudispatch_stats), interface added code to use "down_write_trylock" call to take the dtl_access_lock. The dtl_access_lock is defined in dtl.h file. Also added global reference count variable called "dtl_global_refc", to ensure dtl data can be captured per-cpu. Code also added global lock called "dtl_global_lock" to avoid race condition. Signed-off-by: Kajol Jain <kjain@linux.ibm.com> Tested-by: Tejas Manhas <tejas05@linux.ibm.com> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com> Link: https://patch.msgid.link/20250915102947.26681-3-atrajeev@linux.ibm.com |
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