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Commit2f217d58a8("perf/x86/amd/uncore: Set the thread mask for F17h L3 PMCs") inadvertently changed the uncore driver's behaviour wrt perf tool invocations with or without a CPU list, specified with -C / --cpu=. Change the behaviour of the driver to assume the former all-cpu (-a) case, which is the more commonly desired default. This fixes '-a -A' invocations without explicit cpu lists (-C) to not count L3 events only on behalf of the first thread of the first core in the L3 domain. BEFORE: Activity performed by the first thread of the last core (CPU#43) in CPU#40's L3 domain is not reported by CPU#40: sudo perf stat -a -A -e l3_request_g1.caching_l3_cache_accesses taskset -c 43 perf bench mem memcpy -s 32mb -l 100 -f default ... CPU36 21,835 l3_request_g1.caching_l3_cache_accesses CPU40 87,066 l3_request_g1.caching_l3_cache_accesses CPU44 17,360 l3_request_g1.caching_l3_cache_accesses ... AFTER: The L3 domain activity is now reported by CPU#40: sudo perf stat -a -A -e l3_request_g1.caching_l3_cache_accesses taskset -c 43 perf bench mem memcpy -s 32mb -l 100 -f default ... CPU36 354,891 l3_request_g1.caching_l3_cache_accesses CPU40 1,780,870 l3_request_g1.caching_l3_cache_accesses CPU44 315,062 l3_request_g1.caching_l3_cache_accesses ... Fixes:2f217d58a8("perf/x86/amd/uncore: Set the thread mask for F17h L3 PMCs") Signed-off-by: Kim Phillips <kim.phillips@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200908214740.18097-2-kim.phillips@amd.com
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.