>-----Original Message-----
>From: Daniele Di Proietto [mailto:diproiet...@ovn.org]
>Sent: Wednesday, July 27, 2016 10:10 PM
>To: Kavanagh, Mark B <mark.b.kavan...@intel.com>
>Cc: Bodireddy, Bhanuprakash <bhanuprakash.bodire...@intel.com>;
>dev@openvswitch.org
>Subject: Re: [PATCH v5] netdev-dpdk: Set pmd thread priority
>
>Thanks for the patch, the implementation looks good to me too.
>During testing I kept noticing that it's way too easy to make OVS completely
>unresponsive. As you point out in the documentation by having dpdk-lcore-
>mask the same as pmd-cpu-mask, OVS cannot even be killed (a kill -9 is
>required). I wonder what happens if one tries to set pmd-cpu-mask to every
>core in the system.
>As a way to mitigate the risk perhaps we can avoid setting the main thread
>affinity to the first core in dpdk-lcore-mask by _always_ restoring it in
>dpdk_init__(), also if auto_determine is false.
>Perhaps we should start explicitly prohibiting creating a pmd thread on the
>first core in dpdk-lcore-mask (I get why previous version of this didn't do it
>on
>core 0. Perhaps we can generalize that to the first core in dpdk-lcore-mask).
I will look in to this and get back to you sometime next week.
Regards,
Bhanuprakash.
>
>What's the behavior of other DPDK applications?
>Thanks,
>Daniele
>
>2016-07-27 5:28 GMT-07:00 Kavanagh, Mark B <mark.b.kavan...@intel.com>:
>>
>>Set the DPDK pmd thread scheduling policy to SCHED_RR and static
>>priority to highest priority value of the policy. This is to deal with
>>pmd thread starvation case where another cpu hogging process can get
>>scheduled/affinitized on to the same core the pmd thread is running
>>there by significantly impacting the datapath performance.
>>
>>Setting the realtime scheduling policy to the pmd threads is one step
>>towards Fastpath Service Assurance in OVS DPDK.
>>
>>The realtime scheduling policy is applied only when CPU mask is passed
>>to 'pmd-cpu-mask'. For example:
>>
>> * In the absence of pmd-cpu-mask, one pmd thread shall be created
>> and default scheduling policy and priority gets applied.
>>
>> * If pmd-cpu-mask is specified, one or more pmd threads shall be
>> spawned on the corresponding core(s) in the mask and real time
>> scheduling policy SCHED_RR and highest priority of the policy is
>> applied to the pmd thread(s).
>>
>>To reproduce the pmd thread starvation case:
>>
>>ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=6
>>taskset 0x2 cat /dev/zero > /dev/null &
>>
>>With this commit, it is recommended that the OVS control thread and pmd
>>thread shouldn't be pinned to same core ('dpdk-lcore-mask','pmd-cpu-mask'
>>should be non-overlapping). Also other processes with same affinity as
>>PMD thread will be unresponsive.
>>
>>Signed-off-by: Bhanuprakash Bodireddy
><bhanuprakash.bodire...@intel.com>
>
>LGTM - Acked-by: mark.b.kavan...@intel.com
>
>>---
>>v4->v5:
>>* Reword Note section in DPDK-ADVANCED.md
>>
>>v3->v4:
>>* Document update
>>* Use ovs_strerror for reporting errors in lib-numa.c
>>
>>v2->v3:
>>* Move set_priority() function to lib/ovs-numa.c
>>* Apply realtime scheduling policy and priority to pmd thread only if
>> pmd-cpu-mask is passed.
>>* Update INSTALL.DPDK-ADVANCED.
>>
>>v1->v2:
>>* Removed #ifdef and introduced dummy function
>"pmd_thread_setpriority"
>> in netdev-dpdk.h
>>* Rebase
>>
>> INSTALL.DPDK-ADVANCED.md | 17 +++++++++++++----
>> lib/dpif-netdev.c | 9 +++++++++
>> lib/ovs-numa.c | 18 ++++++++++++++++++
>> lib/ovs-numa.h | 1 +
>> 4 files changed, 41 insertions(+), 4 deletions(-)
>>
>>diff --git a/INSTALL.DPDK-ADVANCED.md b/INSTALL.DPDK-ADVANCED.md
>>index 9ae536d..d76cb4e 100644
>>--- a/INSTALL.DPDK-ADVANCED.md
>>+++ b/INSTALL.DPDK-ADVANCED.md
>>@@ -205,8 +205,10 @@ needs to be affinitized accordingly.
>> pmd thread is CPU bound, and needs to be affinitized to isolated
>> cores for optimum performance.
>>
>>- By setting a bit in the mask, a pmd thread is created and pinned
>>- to the corresponding CPU core. e.g. to run a pmd thread on core 2
>>+ By setting a bit in the mask, a pmd thread is created, pinned
>>+ to the corresponding CPU core and the scheduling policy SCHED_RR
>>+ along with maximum priority of the policy applied to the pmd thread.
>>+ e.g. to pin a pmd thread on core 2
>>
>> `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=4`
>>
>>@@ -234,8 +236,10 @@ needs to be affinitized accordingly.
>> responsible for different ports/rxq's. Assignment of ports/rxq's to
>> pmd threads is done automatically.
>>
>>- A set bit in the mask means a pmd thread is created and pinned
>>- to the corresponding CPU core. e.g. to run pmd threads on core 1 and 2
>>+ A set bit in the mask means a pmd thread is created, pinned to the
>>+ corresponding CPU core and the scheduling policy SCHED_RR with highest
>>+ priority of the scheduling policy applied to pmd thread.
>>+ e.g. to run pmd threads on core 1 and 2
>>
>> `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=6`
>>
>>@@ -246,6 +250,11 @@ needs to be affinitized accordingly.
>>
>> NIC port0 <-> OVS <-> VM <-> OVS <-> NIC port 1
>>
>>+ Note: It is recommended that the OVS control thread and pmd thread
>>+ shouldn't be pinned to same core i.e 'dpdk-lcore-mask' and 'pmd-cpu-
>mask'
>>+ cpu mask settings should be non-overlapping. Also other processes with
>>+ same affinity as PMD thread will be unresponsive.
>>+
>> ### 4.3 DPDK physical port Rx Queues
>>
>> `ovs-vsctl set Interface <DPDK interface> options:n_rxq=<integer>`
>>diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>>index f05ca4e..b85600b 100644
>>--- a/lib/dpif-netdev.c
>>+++ b/lib/dpif-netdev.c
>>@@ -2841,6 +2841,15 @@ pmd_thread_main(void *f_)
>> ovs_numa_thread_setaffinity_core(pmd->core_id);
>> dpdk_set_lcore_id(pmd->core_id);
>> poll_cnt = pmd_load_queues_and_ports(pmd, &poll_list);
>>+
>>+ /* When cpu affinity mask explicitly set using pmd-cpu-mask, pmd
>thread's
>>+ * scheduling policy is set to SCHED_RR and the priority to highest
>>priority
>>+ * of SCHED_RR policy. In the absence of pmd-cpu-mask, default
>scheduling
>>+ * policy and priority shall apply to pmd thread.
>>+ */
>>+ if (pmd->dp->pmd_cmask) {
>>+ ovs_numa_thread_setpriority(SCHED_RR);
>>+ }
>> reload:
>> emc_cache_init(&pmd->flow_cache);
>>
>>diff --git a/lib/ovs-numa.c b/lib/ovs-numa.c
>>index c8173e0..428f274 100644
>>--- a/lib/ovs-numa.c
>>+++ b/lib/ovs-numa.c
>>@@ -613,3 +613,21 @@ int ovs_numa_thread_setaffinity_core(unsigned
>core_id OVS_UNUSED)
>> return EOPNOTSUPP;
>> #endif /* __linux__ */
>> }
>>+
>>+void
>>+ovs_numa_thread_setpriority(int policy)
>>+{
>>+ if (dummy_numa) {
>>+ return;
>>+ }
>>+
>>+ struct sched_param threadparam;
>>+ int err;
>>+
>>+ memset(&threadparam, 0, sizeof(threadparam));
>>+ threadparam.sched_priority = sched_get_priority_max(policy);
>>+ err = pthread_setschedparam(pthread_self(), policy, &threadparam);
>>+ if (err) {
>>+ VLOG_ERR("Thread priority error %s",ovs_strerror(err));
>>+ }
>>+}
>>diff --git a/lib/ovs-numa.h b/lib/ovs-numa.h
>>index be836b2..94f0884 100644
>>--- a/lib/ovs-numa.h
>>+++ b/lib/ovs-numa.h
>>@@ -56,6 +56,7 @@ void ovs_numa_unpin_core(unsigned core_id);
>> struct ovs_numa_dump *ovs_numa_dump_cores_on_numa(int numa_id);
>> void ovs_numa_dump_destroy(struct ovs_numa_dump *);
>> int ovs_numa_thread_setaffinity_core(unsigned core_id);
>>+void ovs_numa_thread_setpriority(int policy);
>>
>> #define FOR_EACH_CORE_ON_NUMA(ITER, DUMP) \
>> LIST_FOR_EACH((ITER), list_node, &(DUMP)->dump)
>>--
>>2.4.11
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