From: Sebastian Andrzej Siewior Date: Thu, 4 Jul 2024 19:03:38 +0200 Subject: [PATCH 4/7] perf: Shrink the size of the recursion counter. Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz There are four recursion counter, one for each context. The type of the counter is `int' but the counter is used as `bool' since it is only incremented if zero. The main goal here is to shrink the whole struct into 32bit int which can later be added task_struct into an existing hole. Reduce the type of the recursion counter to an unsigned char, keep the increment/ decrement operation. Tested-by: Marco Elver Link: https://lore.kernel.org/20240621091601.18227-1-frederic@kernel.org Link: https://lore.kernel.org/r/20240704170424.1466941-5-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior --- kernel/events/callchain.c | 2 +- kernel/events/core.c | 2 +- kernel/events/internal.h | 4 ++-- 3 files changed, 4 insertions(+), 4 deletions(-) --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -29,7 +29,7 @@ static inline size_t perf_callchain_entr sysctl_perf_event_max_contexts_per_stack)); } -static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); +static DEFINE_PER_CPU(u8, callchain_recursion[PERF_NR_CONTEXTS]); static atomic_t nr_callchain_events; static DEFINE_MUTEX(callchain_mutex); static struct callchain_cpus_entries *callchain_cpus_entries; --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9776,7 +9776,7 @@ struct swevent_htable { int hlist_refcount; /* Recursion avoidance in each contexts */ - int recursion[PERF_NR_CONTEXTS]; + u8 recursion[PERF_NR_CONTEXTS]; }; static DEFINE_PER_CPU(struct swevent_htable, swevent_htable); --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -208,7 +208,7 @@ arch_perf_out_copy_user(void *dst, const DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user) -static inline int get_recursion_context(int *recursion) +static inline int get_recursion_context(u8 *recursion) { unsigned char rctx = interrupt_context_level(); @@ -221,7 +221,7 @@ static inline int get_recursion_context( return rctx; } -static inline void put_recursion_context(int *recursion, int rctx) +static inline void put_recursion_context(u8 *recursion, int rctx) { barrier(); recursion[rctx]--;