I found a crash if apply this patch, "dpdk-lcore-mask" is not set and "-c
0x1" is passed to "dpdk-extra".
Also, I believe Flavio had a comment on the previous version of this
patch. Would it be enough to use setpriority(2)?
Thanks,
Daniele
2016-08-15 8:19 GMT-07:00 Bhanuprakash Bodireddy <
bhanuprakash.bodire...@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. 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 &
>
> 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).
>
> 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). If dpdk-lcore-mask is set same as pmd-cpu-mask
> the pmd thread is not spawned on lowest core of the dpdk-lcore-mask.
> Also other processes with same affinity as PMD thread will be unresponsive.
>
> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodire...@intel.com>
> ---
> v5->v6:
> * Prohibit spawning pmd thread on the lowest core in dpdk-lcore-mask if
> lcore-mask and pmd-mask affinity are identical.
> * Updated Note section in INSTALL.DPDK-ADVANCED doc.
> * Tested below cases to verify system stability with pmd priority patch
>
> dpdk-lcore-mask | pmd-cpu-mask | Comment
> 1. Not set | Not set | control threads affinity: 0-27
> pmd thread: core 0
> 2. 1 | 1 | pmd thread isn't spawned and warning
> logged in logfile.
> 3. 1 | c |
> 4. F0 | F0 | control threads pinned to core 4.
> 3 pmd threads created on core 5,6,7
> but 4.
>
> 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 | 24 ++++++++++++++++++++----
> lib/dpif-netdev.c | 12 ++++++++++++
> lib/netdev-dpdk.c | 22 ++++++++++++++++++++++
> lib/ovs-numa.c | 18 ++++++++++++++++++
> lib/ovs-numa.h | 1 +
> 5 files changed, 73 insertions(+), 4 deletions(-)
>
> diff --git a/INSTALL.DPDK-ADVANCED.md b/INSTALL.DPDK-ADVANCED.md
> index dd36ae4..f039723 100755
> --- a/INSTALL.DPDK-ADVANCED.md
> +++ b/INSTALL.DPDK-ADVANCED.md
> @@ -208,8 +208,10 @@ 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`
>
> @@ -237,8 +239,10 @@ 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`
>
> @@ -249,6 +253,18 @@ needs to be affinitized accordingly.
>
> NIC port0 <-> OVS <-> VM <-> OVS <-> NIC port 1
>
> + Note: 'dpdk-lcore-mask' and 'pmd-cpu-mask' cpu mask settings should be
> + non-overlapping. If you set dpdk-lcore-mask same as pmd-cpu-mask, the
> pmd
> + thread is not spawned on lowest core of the dpdk-lcore-mask and in case
> of
> + cpu mask setting where both the control and the pmd thread pinned to
> same
> + core, pmd thread is not spawned at all if it is the only cpu in the
> affinity
> + mask.
> +
> + For example, if dpdk-lcore-mask=F0 and pmd-cpu-mask=F0, pmd threads are
> + created on cores 5, 6, and 7 but not on 4. Setting both lcore,pmd mask
> to
> + core 4 shall pin control threads to core 4 but will prevent pmd thread
> from
> + spawning.
> +
> ### 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 96504f5..abe1fde 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -3100,6 +3100,18 @@ 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 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 dpdk-lcore-mask is set same as pmd-cpu-mask, the pmd thread is
> not
> + * spawned on lowest core of the dpdk-lcore-mask.
> + */
> + if (pmd->dp->pmd_cmask) {
> + ovs_numa_thread_setpriority(SCHED_RR);
> + }
> reload:
> emc_cache_init(&pmd->flow_cache);
>
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index c767fd4..5d606a2 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -3432,6 +3432,28 @@ dpdk_init__(const struct smap *ovs_other_config)
> }
> }
>
> + /* If dpdk-lcore-mask is explicitly specified, auto_determine is
> 'false'
> + * and control threads are pinned to lowest core of the affinity mask.
> + * Mark the corresponding control thread 'core->pinned' status to
> 'true'
> + * so that pmd thread can't be spawned on the same core.
> + */
> + if (!auto_determine) {
> + const char *lcore_mask;
> + unsigned int core_id;
> + int dl_mask;
> +
> + lcore_mask = smap_get(ovs_other_config, "dpdk-lcore-mask");
> + dl_mask = strtol(lcore_mask, NULL, 16);
> +
> + /* Get the lowest core_id of dpdk-lcore-mask */
> + core_id = rightmost_1bit_idx(dl_mask);
> +
> + /* Set the control thread core 'pinned' status to true */
> + if (!ovs_numa_try_pin_core_specific(core_id)) {
> + VLOG_ERR("Unable to pin core %d", core_id);
> + }
> + }
> +
> dpdk_argv = argv;
> dpdk_argc = argc;
>
> 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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