>-----Original Message-----
>From: Daniele Di Proietto [mailto:[email protected]]
>Sent: Tuesday, August 16, 2016 1:44 AM
>To: Bodireddy, Bhanuprakash <[email protected]>
>Cc: [email protected]; Flavio Leitner <[email protected]>
>Subject: Re: [PATCH V6] netdev-dpdk: Set pmd thread priority
>
>I found a crash if apply this patch, "dpdk-lcore-mask" is not set and "-c 0x1"
>is
>passed to "dpdk-extra".
My bad, I didn't test with dpdk-extra options. I see that the crash was due to
strtol.
>Also, I believe Flavio had a comment on the previous version of this
>patch. Would it be enough to use setpriority(2)?
I sent out my comments in another mail. I agree to Flavio's suggestion as this
seems less dangerous and
is guaranteed to work even in case of misconfiguration. I tested this approach
and have a concern with
setpriority().
To apply the new nice value to the thread, thread id is needed and due to
absence of glibc wrapper
for gettid, I have to use syscall(SYS_gettid). I want to know if this is
acceptable in OVS or better way to handle this?
Void ovs_numa_thread_setpriority(int nice OVS_UNUSED)
{
....
#if defined(__linux__) && defined(SYS_gettid)
pid_t tid = syscall(SYS_gettid);
err = setpriority(PRIO_PROCESS, tid, nice);
....
#endif
}
Without priority patch:
$ ps -eLo tid,pri,psr,comm | grep -e lcore -e revalidator -e ovs-vswitchd -e pmd
22509 19 4 ovs-vswitchd
22512 19 5 lcore-slave-5
22513 19 6 lcore-slave-6
22514 19 7 lcore-slave-7
22589 19 4 revalidator37
22590 19 4 revalidator52
22591 19 4 revalidator42
22592 19 4 revalidator38
22593 19 4 revalidator39
22594 19 4 revalidator45
22595 19 4 revalidator53
22596 19 4 revalidator54
22598 19 4 pmd61 [Default priority]
With priority patch:
$ ps -eLo tid,pri,psr,comm | grep -e lcore -e revalidator -e ovs-vswitchd -e pmd
24879 19 4 ovs-vswitchd
24881 19 5 lcore-slave-5
24882 19 6 lcore-slave-6
24883 19 7 lcore-slave-7
24951 19 4 revalidator55
24952 19 4 revalidator37
24953 19 4 revalidator52
24954 19 4 revalidator42
24955 19 4 revalidator38
24956 19 4 revalidator39
24957 19 4 revalidator45
24958 19 4 revalidator53
24964 39 4 pmd61 [Higher priority set]
Regards,
Bhanu Prakash.
>Thanks,
>Daniele
>
>2016-08-15 8:19 GMT-07:00 Bhanuprakash Bodireddy
><[email protected]>:
>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
><[email protected]>
>---
>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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