From: Harry van Haaren <harry.van.haaren@intel.com>
To: dev@dpdk.org
Cc: "Harry van Haaren" <harry.van.haaren@intel.com>,
"Mattias Rönnblom" <mattias.ronnblom@ericsson.com>,
"Honnappa Nagarahalli" <Honnappa.Nagarahalli@arm.com>,
"Morten Brørup" <mb@smartsharesystems.com>
Subject: [PATCH 2/2] service: fix potential stats race-condition on MT services
Date: Fri, 8 Jul 2022 12:56:45 +0000 [thread overview]
Message-ID: <20220708125645.3141464-2-harry.van.haaren@intel.com> (raw)
In-Reply-To: <20220708125645.3141464-1-harry.van.haaren@intel.com>
This commit fixes a potential racey-add that could occur if
multiple service-lcores were executing the same MT-safe service
at the same time, with service statistics collection enabled.
Because multiple threads can run and execute the service, the
stats values can have multiple writer threads, resulting in the
requirement of using atomic addition for correctness.
Note that when a MT unsafe service is executed, a spinlock is
held, so the stats increments are protected. This fact is used
to avoid executing atomic add instructions when not required.
This patch causes a 1.25x increase in cycle-cost for polling a
MT safe service when statistics are enabled. No change was seen
for MT unsafe services, or when statistics are disabled.
Reported-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Suggested-by: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Suggested-by: Morten Brørup <mb@smartsharesystems.com>
Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
---
---
lib/eal/common/rte_service.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/lib/eal/common/rte_service.c b/lib/eal/common/rte_service.c
index ef31b1f63c..f045e74ef3 100644
--- a/lib/eal/common/rte_service.c
+++ b/lib/eal/common/rte_service.c
@@ -363,9 +363,15 @@ service_runner_do_callback(struct rte_service_spec_impl *s,
uint64_t start = rte_rdtsc();
s->spec.callback(userdata);
uint64_t end = rte_rdtsc();
- s->cycles_spent += end - start;
+ uint64_t cycles = end - start;
cs->calls_per_service[service_idx]++;
- s->calls++;
+ if (service_mt_safe(s)) {
+ __atomic_fetch_add(&s->cycles_spent, cycles, __ATOMIC_RELAXED);
+ __atomic_fetch_add(&s->calls, 1, __ATOMIC_RELAXED);
+ } else {
+ s->cycles_spent += cycles;
+ s->calls++;
+ }
} else
s->spec.callback(userdata);
}
--
2.32.0
next prev parent reply other threads:[~2022-07-08 12:57 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-08 12:56 [PATCH 1/2] test/service: add perf measurements for with stats mode Harry van Haaren
2022-07-08 12:56 ` Harry van Haaren [this message]
2022-07-08 13:23 ` [PATCH 2/2] service: fix potential stats race-condition on MT services Morten Brørup
2022-07-08 13:44 ` Van Haaren, Harry
2022-07-08 14:14 ` Morten Brørup
2022-07-08 13:48 ` Mattias Rönnblom
2022-07-08 15:16 ` Honnappa Nagarahalli
2022-07-08 15:31 ` Van Haaren, Harry
2022-07-08 16:21 ` Bruce Richardson
2022-07-08 16:33 ` Honnappa Nagarahalli
2022-07-08 20:02 ` Mattias Rönnblom
2022-07-08 16:29 ` Morten Brørup
2022-07-08 16:45 ` Honnappa Nagarahalli
2022-07-08 17:22 ` Morten Brørup
2022-07-08 17:39 ` Honnappa Nagarahalli
2022-07-08 18:08 ` Morten Brørup
2022-09-06 16:13 ` [PATCH 1/6] service: reduce statistics overhead for parallel services Mattias Rönnblom
2022-09-06 16:13 ` [PATCH 2/6] service: introduce per-lcore cycles counter Mattias Rönnblom
2022-09-06 16:13 ` [PATCH 3/6] service: reduce average case service core overhead Mattias Rönnblom
2022-10-03 13:33 ` Van Haaren, Harry
2022-10-03 14:32 ` Mattias Rönnblom
2022-09-06 16:13 ` [PATCH 4/6] service: tweak cycle statistics semantics Mattias Rönnblom
2022-09-07 8:41 ` Morten Brørup
2022-10-03 13:45 ` Van Haaren, Harry
2022-09-06 16:13 ` [PATCH 5/6] event/sw: report idle when no work is performed Mattias Rönnblom
2022-09-06 16:13 ` [PATCH 6/6] service: provide links to functions in documentation Mattias Rönnblom
2022-10-03 8:06 ` [PATCH 1/6] service: reduce statistics overhead for parallel services David Marchand
2022-10-03 8:40 ` Mattias Rönnblom
2022-10-03 9:53 ` David Marchand
2022-10-03 11:37 ` Mattias Rönnblom
2022-10-03 13:03 ` Van Haaren, Harry
2022-10-03 13:33 ` Van Haaren, Harry
2022-10-03 14:37 ` Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 0/6] Service cores performance and statistics improvements Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 1/6] service: reduce statistics overhead for parallel services Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 2/6] service: introduce per-lcore cycles counter Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 3/6] service: reduce average case service core overhead Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 4/6] service: tweak cycle statistics semantics Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 5/6] event/sw: report idle when no work is performed Mattias Rönnblom
2022-10-05 9:16 ` [PATCH v2 6/6] service: provide links to functions in documentation Mattias Rönnblom
2022-10-05 9:49 ` [PATCH v2 0/6] Service cores performance and statistics improvements Morten Brørup
2022-10-05 10:14 ` Mattias Rönnblom
2022-10-05 13:39 ` David Marchand
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