The patch titled Subject: bounds: support non-power-of-two CONFIG_NR_CPUS has been added to the -mm mm-nonmm-unstable branch. Its filename is bounds-support-non-power-of-two-config_nr_cpus.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: "Matthew Wilcox (Oracle)" willy@infradead.org Subject: bounds: support non-power-of-two CONFIG_NR_CPUS Date: Tue, 10 Oct 2023 15:55:49 +0100
ilog2() rounds down, so for example when PowerPC 85xx sets CONFIG_NR_CPUS to 24, we will only allocate 4 bits to store the number of CPUs instead of 5. Use bits_per() instead, which rounds up. Found by code inspection. The effect of this would probably be a misaccounting when doing NUMA balancing, so to a user, it would only be a performance penalty. The effects may be more wide-spread; it's hard to tell.
Link: https://lkml.kernel.org/r/20231010145549.1244748-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Fixes: 90572890d202 ("mm: numa: Change page last {nid,pid} into {cpu,pid}") Reviewed-by: Rik van Riel riel@surriel.com Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Peter Zijlstra peterz@infradead.org Cc: Ingo Molnar mingo@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
kernel/bounds.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/bounds.c~bounds-support-non-power-of-two-config_nr_cpus +++ a/kernel/bounds.c @@ -19,7 +19,7 @@ int main(void) DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS); DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES); #ifdef CONFIG_SMP - DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS)); + DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS)); #endif DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t)); #ifdef CONFIG_LRU_GEN _
Patches currently in -mm which might be from willy@infradead.org are
bounds-support-non-power-of-two-config_nr_cpus.patch