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authorGautham R. Shenoy <ego@linux.vnet.ibm.com>2020-12-10 11:38:58 +0100
committerMichael Ellerman <mpe@ellerman.id.au>2020-12-10 14:10:25 +0100
commit9538abee18cca70ffd03cef56027388b0c5084cc (patch)
tree03c06dbb74aa7665945716bd37e0be69fa006031 /arch/powerpc/kernel/cacheinfo.c
parentpowerpc/smp: Rename init_thread_group_l1_cache_map() to make it generic (diff)
downloadlinux-9538abee18cca70ffd03cef56027388b0c5084cc.tar.xz
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powerpc/smp: Add support detecting thread-groups sharing L2 cache
On POWER systems, groups of threads within a core sharing the L2-cache can be indicated by the "ibm,thread-groups" property array with the identifier "2". This patch adds support for detecting this, and when present, populate the populating the cpu_l2_cache_mask of every CPU to the core-siblings which share L2 with the CPU as specified in the by the "ibm,thread-groups" property array. On a platform with the following "ibm,thread-group" configuration 00000001 00000002 00000004 00000000 00000002 00000004 00000006 00000001 00000003 00000005 00000007 00000002 00000002 00000004 00000000 00000002 00000004 00000006 00000001 00000003 00000005 00000007 Without this patch, the sched-domain hierarchy for CPUs 0,1 would be CPU0 attaching sched-domain(s): domain-0: span=0,2,4,6 level=SMT domain-1: span=0-7 level=CACHE domain-2: span=0-15,24-39,48-55 level=MC domain-3: span=0-55 level=DIE CPU1 attaching sched-domain(s): domain-0: span=1,3,5,7 level=SMT domain-1: span=0-7 level=CACHE domain-2: span=0-15,24-39,48-55 level=MC domain-3: span=0-55 level=DIE The CACHE domain at 0-7 is incorrect since the ibm,thread-groups sub-array [00000002 00000002 00000004 00000000 00000002 00000004 00000006 00000001 00000003 00000005 00000007] indicates that L2 (Property "2") is shared only between the threads of a single group. There are "2" groups of threads where each group contains "4" threads each. The groups being {0,2,4,6} and {1,3,5,7}. With this patch, the sched-domain hierarchy for CPUs 0,1 would be CPU0 attaching sched-domain(s): domain-0: span=0,2,4,6 level=SMT domain-1: span=0-15,24-39,48-55 level=MC domain-2: span=0-55 level=DIE CPU1 attaching sched-domain(s): domain-0: span=1,3,5,7 level=SMT domain-1: span=0-15,24-39,48-55 level=MC domain-2: span=0-55 level=DIE The CACHE domain with span=0,2,4,6 for CPU 0 (span=1,3,5,7 for CPU 1 resp.) gets degenerated into the SMT domain. Furthermore, the last-level-cache domain gets correctly set to the SMT sched-domain. Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1607596739-32439-5-git-send-email-ego@linux.vnet.ibm.com
Diffstat (limited to 'arch/powerpc/kernel/cacheinfo.c')
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