From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
To: "Eads, Gage" <gage.eads@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: "jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
"nipun.gupta@nxp.com" <nipun.gupta@nxp.com>,
"santosh.shukla@caviumnetworks.com"
<santosh.shukla@caviumnetworks.com>,
"pbhagavatula@caviumnetworks.com"
<pbhagavatula@caviumnetworks.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] event/sw: use dynamically-sized IQs
Date: Thu, 7 Dec 2017 17:15:35 +0000 [thread overview]
Message-ID: <E923DB57A917B54B9182A2E928D00FA650FDEC43@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <1512011314-19682-2-git-send-email-gage.eads@intel.com>
> From: Eads, Gage
> Sent: Thursday, November 30, 2017 3:09 AM
> To: dev@dpdk.org
> Cc: jerin.jacob@caviumnetworks.com; Van Haaren, Harry
> <harry.van.haaren@intel.com>; Richardson, Bruce
> <bruce.richardson@intel.com>; hemant.agrawal@nxp.com; nipun.gupta@nxp.com;
> santosh.shukla@caviumnetworks.com; pbhagavatula@caviumnetworks.com
> Subject: [PATCH 2/2] event/sw: use dynamically-sized IQs
>
> This commit introduces dynamically-sized IQs, by switching the underlying
> data structure from a fixed-size ring to a linked list of queue 'chunks.'
> This has a number of benefits:
> - Certain corner cases were observed in which all of a pipeline's flows
> could be pinned to one port for extended periods, effectively turning a
> multi-core pipeline into single-core one. This was caused by an event
> producer having a larger new_event_threshold than the IQ depth, and
> injecting large numbers of packets that are ultimately backpressured in a
> worker's rx_ring, causing those packets' flows to be scheduled to that
> port.
> The dynamically sized IQ does not have this problem because each IQ can
> grow large enough to store all the system's events, such that
> backpressure will not reach the worker_ring.
> - Slight performance improvement (~1-2%) in high throughput scenarios,
> tested with eventdev_pipeline_sw_pmd.
>
> This implementation has a small increase in the queue storage memory
> footprint (~70KB). This commit also removes the iq_size xstat, which no
> longer applies to this implementation.
>
> Signed-off-by: Gage Eads <gage.eads@intel.com>
Some review notes below - but nothing that needs changing.
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>
> diff --git a/drivers/event/sw/sw_evdev.c b/drivers/event/sw/sw_evdev.c
<snip>
> - for (i = 0; i < SW_IQS_MAX; i++) {
> - snprintf(buf, sizeof(buf), "q_%u_iq_%d", idx, i);
> - qid->iq[i] = iq_ring_create(buf, socket_id);
> - if (!qid->iq[i]) {
> - SW_LOG_DBG("ring create failed");
> - goto cleanup;
> - }
> - }
> + for (i = 0; i < SW_IQS_MAX; i++)
> + iq_init(sw, &qid->iq[i]);
Review notes;
- It looks like error checking is being lost above, but in reality the iq_init() cannot fail in this new scheme, provided that the pool of chunks is provisioned correctly at configure() time (see provisioning below).
No action required here - just noting this error-checking change.
> + /* Number of chunks sized for worst-case spread of events across IQs */
> + num_chunks = ((SW_INFLIGHT_EVENTS_TOTAL/SW_EVS_PER_Q_CHUNK)+1) +
> + sw->qid_count*SW_IQS_MAX*2;
To verify the logic here;
((TOTAL / CHUNK_SIZE) + 1) is the main body of chunks.
QID * IQ * 2 is there so each QID can hold a chunk, and a next pointer, for each priority of IQ.
add these two together, is the total number of chunks. Check :)
next prev parent reply other threads:[~2017-12-07 17:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 3:08 [dpdk-dev] [PATCH 1/2] event/sw: fix queue memory leak and multi-link bug Gage Eads
2017-11-30 3:08 ` [dpdk-dev] [PATCH 2/2] event/sw: use dynamically-sized IQs Gage Eads
2017-12-07 17:15 ` Van Haaren, Harry [this message]
2017-12-09 9:26 ` Jerin Jacob
2018-01-08 15:32 ` Pavan Nikhilesh
2018-01-08 15:50 ` Van Haaren, Harry
2018-01-08 16:05 ` Pavan Nikhilesh
2018-01-08 18:36 ` Eads, Gage
2018-01-09 7:12 ` Pavan Nikhilesh
2017-12-07 17:15 ` [dpdk-dev] [PATCH 1/2] event/sw: fix queue memory leak and multi-link bug Van Haaren, Harry
2017-12-09 9:26 ` Jerin Jacob
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