perf: Improve the perf_sample_data struct layout

This patch reorders fields in the perf_sample_data struct in order to
minimize the number of cachelines touched in perf_sample_data_init().
It also removes some intializations which are redundant with the code
in kernel/events/core.c

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1411559322-16548-7-git-send-email-eranian@google.com
Cc: cebbert.lkml@gmail.com
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: jolsa@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 25 insertions, 25 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 68d46d536e24..486e84ccb1f9 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -580,35 +580,40 @@ extern u64 perf_event_read_value(struct perf_event *event,
 
 
 struct perf_sample_data {
-        u64                             type;
+        /*
+         * Fields set by perf_sample_data_init(), group so as to
+         * minimize the cachelines touched.
+         */
+        u64                             addr;
+        struct perf_raw_record          *raw;
+        struct perf_branch_stack        *br_stack;
+        u64                             period;
+        u64                             weight;
+        u64                             txn;
+        union  perf_mem_data_src        data_src;
 
+        /*
+         * The other fields, optionally {set,used} by
+         * perf_{prepare,output}_sample().
+         */
+        u64                             type;
         u64                             ip;
         struct {
                 u32     pid;
                 u32     tid;
         }                               tid_entry;
         u64                             time;
-        u64                             addr;
         u64                             id;
         u64                             stream_id;
         struct {
                 u32     cpu;
                 u32     reserved;
         }                               cpu_entry;
-        u64                             period;
-        union  perf_mem_data_src        data_src;
         struct perf_callchain_entry     *callchain;
-        struct perf_raw_record          *raw;
-        struct perf_branch_stack        *br_stack;
         struct perf_regs                regs_user;
         struct perf_regs                regs_intr;
         u64                             stack_user_size;
-        u64                             weight;
-        /*
-         * Transaction flags for abort events:
-         */
-        u64                             txn;
-};
+} ____cacheline_aligned;
 
 /* default value for data source */
 #define PERF_MEM_NA (PERF_MEM_S(OP, NA)   |\
@@ -625,14 +630,9 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
         data->raw  = NULL;
         data->br_stack = NULL;
         data->period = period;
-        data->regs_user.abi = PERF_SAMPLE_REGS_ABI_NONE;
-        data->regs_user.regs = NULL;
-        data->stack_user_size = 0;
         data->weight = 0;
         data->data_src.val = PERF_MEM_NA;
         data->txn = 0;
-        data->regs_intr.abi = PERF_SAMPLE_REGS_ABI_NONE;
-        data->regs_intr.regs = NULL;
 }
 
 extern void perf_output_sample(struct perf_output_handle *handle,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index c2be1597ece7..3e19d3ebc29c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4471,8 +4471,11 @@ static void perf_sample_regs_user(struct perf_regs *regs_user,
         }
 
         if (regs) {
-                regs_user->regs = regs;
                 regs_user->abi  = perf_reg_abi(current);
+                regs_user->regs = regs;
+        } else {
+                regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
+                regs_user->regs = NULL;
         }
 }
 
@@ -4947,12 +4950,13 @@ void perf_prepare_sample(struct perf_event_header *header,
                 header->size += size;
         }
 
+        if (sample_type & (PERF_SAMPLE_REGS_USER | PERF_SAMPLE_STACK_USER))
+                perf_sample_regs_user(&data->regs_user, regs);
+
         if (sample_type & PERF_SAMPLE_REGS_USER) {
                 /* regs dump ABI info */
                 int size = sizeof(u64);
 
-                perf_sample_regs_user(&data->regs_user, regs);
-
                 if (data->regs_user.regs) {
                         u64 mask = event->attr.sample_regs_user;
                         size += hweight64(mask) * sizeof(u64);
@@ -4968,15 +4972,11 @@ void perf_prepare_sample(struct perf_event_header *header,
                  * in case new sample type is added, because we could eat
                  * up the rest of the sample size.
                  */
-                struct perf_regs *uregs = &data->regs_user;
                 u16 stack_size = event->attr.sample_stack_user;
                 u16 size = sizeof(u64);
 
-                if (!uregs->abi)
-                        perf_sample_regs_user(uregs, regs);
-
                 stack_size = perf_sample_ustack_size(stack_size, header->size,
-                                                     uregs->regs);
+                                                     data->regs_user.regs);
 
                 /*
                  * If there is something to dump, add space for the dump