[PATCH v2 2/2] perf mem: Support HITM for when mem_lvl_num is used

Ali Saidi
2022-02-21T22:48:54Z

Current code only support HITM statistics for last level cache (LLC)
when mem_lvl encodes the level. On existing Arm64 machines there are as
many as four levels cache and this change supports decoding l1, l2, and
llc hits from the mem_lvl_num data. Given that the mem_lvl namespace is
being deprecated take this opportunity to encode the neoverse data into
mem_lvl_num.

For loads that hit in a the LLC snoop filter and are fullfilled from a
higher level cache, it's not usually clear what the true level of the
cache the data came from (i.e. a transfer from a core could come from
it's L1 or L2). Instead of making an assumption of where the line came
from, add support for incrementing HITM if the source is CACHE_ANY.

Since other architectures don't seem to populate the mem_lvl_num field
here there shouldn't be a change in functionality.

Signed-off-by: Ali Saidi <alisaidi@amazon.com>
---
tools/perf/util/mem-events.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
index ed0ab838bcc5..6c3fd4aac7ae 100644
--- a/tools/perf/util/mem-events.c
+++ b/tools/perf/util/mem-events.c
@@ -485,6 +485,7 @@ int c2c_decode_stats(struct c2c_stats *stats, struct mem_info *mi)
u64 daddr = mi->daddr.addr;
u64 op = data_src->mem_op;
u64 lvl = data_src->mem_lvl;
+ u64 lnum = data_src->mem_lvl_num;
u64 snoop = data_src->mem_snoop;
u64 lock = data_src->mem_lock;
u64 blk = data_src->mem_blk;
@@ -527,16 +528,18 @@ do { \
if (lvl & P(LVL, UNC)) stats->ld_uncache++;
if (lvl & P(LVL, IO)) stats->ld_io++;
if (lvl & P(LVL, LFB)) stats->ld_fbhit++;
- if (lvl & P(LVL, L1 )) stats->ld_l1hit++;
- if (lvl & P(LVL, L2 )) stats->ld_l2hit++;
- if (lvl & P(LVL, L3 )) {
+ if (lvl & P(LVL, L1) || lnum == P(LVLNUM, L1))
+ stats->ld_l1hit++;
+ if (lvl & P(LVL, L2) || lnum == P(LVLNUM, L2))
+ stats->ld_l2hit++;
+ if (lvl & P(LVL, L3) || lnum == P(LVLNUM, L4)) {
if (snoop & P(SNOOP, HITM))
HITM_INC(lcl_hitm);
else
stats->ld_llchit++;
}

- if (lvl & P(LVL, LOC_RAM)) {
+ if (lvl & P(LVL, LOC_RAM) || lnum == P(LVLNUM, RAM)) {
stats->lcl_dram++;
if (snoop & P(SNOOP, HIT))
stats->ld_shared++;
@@ -564,6 +567,9 @@ do { \
HITM_INC(rmt_hitm);
}

+ if (lnum == P(LVLNUM, ANY_CACHE) && snoop & P(SNOOP, HITM))
+ HITM_INC(lcl_hitm);
+
if ((lvl & P(LVL, MISS)))
stats->ld_miss++;

--
2.32.0