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Athira Rajeev a1ca0cbbf7 powerpc/perf: Fix power9 event alternatives [ Upstream commit `0dcad700bb` ] When scheduling a group of events, there are constraint checks done to make sure all events can go in a group. Example, one of the criteria is that events in a group cannot use the same PMC. But platform specific PMU supports alternative event for some of the event codes. During perf_event_open(), if any event group doesn't match constraint check criteria, further lookup is done to find alternative event. By current design, the array of alternatives events in PMU code is expected to be sorted by column 0. This is because in find_alternative() the return criteria is based on event code comparison. ie. "event < ev_alt[i][0])". This optimisation is there since find_alternative() can be called multiple times. In power9 PMU code, the alternative event array is not sorted properly and hence there is breakage in finding alternative events. To work with existing logic, fix the alternative event array to be sorted by column 0 for power9-pmu.c Results: With alternative events, multiplexing can be avoided. That is, for example, in power9 PM_LD_MISS_L1 (0x3e054) has alternative event, PM_LD_MISS_L1_ALT (0x400f0). This is an identical event which can be programmed in a different PMC. Before: # perf stat -e r3e054,r300fc Performance counter stats for 'system wide': 1057860 r3e054 (50.21%) 379 r300fc (49.79%) 0.944329741 seconds time elapsed Since both the events are using PMC3 in this case, they are multiplexed here. After: # perf stat -e r3e054,r300fc Performance counter stats for 'system wide': 1006948 r3e054 182 r300fc Fixes: `91e0bd1e62` ("powerpc/perf: Add PM_LD_MISS_L1 and PM_BR_2PATH to power9 event list") Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com> Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220419114828.89843-1-atrajeev@linux.vnet.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-04-27 14:41:13 +02:00
arch	powerpc/perf: Fix power9 event alternatives	2022-04-27 14:41:13 +02:00
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drivers	drm/vc4: Use pm_runtime_resume_and_get to fix pm_runtime_get_sync() usage	2022-04-27 14:41:13 +02:00
fs	io_uring: free iovec if file assignment fails	2022-04-27 14:41:12 +02:00
include	oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup	2022-04-27 14:41:11 +02:00
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kernel	perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled	2022-04-27 14:41:12 +02:00
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mm	mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()	2022-04-27 14:41:11 +02:00
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README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.