From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>,
"Harry van Haaren" <harry.van.haaren@intel.com>
Cc: <dev@dpdk.org>,
"Honnappa Nagarahalli" <Honnappa.Nagarahalli@arm.com>,
"nd" <nd@arm.com>
Subject: RE: [PATCH 4/6] service: tweak cycle statistics semantics
Date: Wed, 7 Sep 2022 10:41:25 +0200 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D872FE@smartserver.smartshare.dk> (raw)
In-Reply-To: <20220906161352.296110-4-mattias.ronnblom@ericsson.com>
> From: Mattias Rönnblom [mailto:mattias.ronnblom@ericsson.com]
> Sent: Tuesday, 6 September 2022 18.14
>
> As a part of its service function, a service usually polls some kind
> of source (e.g., an RX queue, a ring, an eventdev port, or a timer
> wheel) to retrieve one or more items of work.
>
> In low-load situations, the service framework reports a significant
> amount of cycles spent for all running services, despite the fact they
> have performed little or no actual work.
>
> The per-call cycle expenditure for an idle service (i.e., a service
> currently without pending jobs) is typically very low. Polling an
> empty ring or RX queue is inexpensive. However, since the service
> function call frequency on an idle or lightly loaded lcore is going to
> be very high indeed, the service function calls' cycles adds up to a
> significant amount. The only thing preventing the idle services'
> cycles counters to make up 100% of the available CPU cycles is the
> overhead of the service framework itself.
>
> If the RTE_SERVICE_ATTR_CYCLES or RTE_SERVICE_LCORE_ATTR_CYCLES are
> used to estimate service core load, the cores may look very busy when
> the system is mostly doing nothing useful at all.
>
> This patch allows for an idle service to indicate that no actual work
> was performed during a particular service function call (by returning
> -EAGAIN). In such cases the RTE_SERVICE_ATTR_CYCLES and
> RTE_SERVICE_LCORE_ATTR_CYCLES values are not incremented.
>
> The convention of returning -EAGAIN for idle services may in the
> future also be used to have the lcore enter a short sleep, or reduce
> its operating frequency, in case all services are currently idle.
>
> This change is backward-compatible.
>
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> ---
This entire series contains a bunch of good improvements.
Returning -EAGAIN is a step in the right direction towards measuring CPU usage, and a great way to make it backwards compatible.
Series-Acked-by: Morten Brørup <mb@smartsharesystems.com>
next prev parent reply other threads:[~2022-09-07 8:41 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 ` [PATCH 2/2] service: fix potential stats race-condition on MT services Harry van Haaren
2022-07-08 13:23 ` 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 [this message]
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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