[ovs-dev] [PATCH v6 1/5] netdev-dpdk: fix management of pre-existing mempools.

Fischetti, Antonio antonio.fischetti at intel.com
Tue Oct 17 17:04:04 UTC 2017


Thanks Mark, comments inline.

-Antonio

> -----Original Message-----
> From: Kavanagh, Mark B
> Sent: Tuesday, October 17, 2017 2:34 PM
> To: Fischetti, Antonio <antonio.fischetti at intel.com>; dev at openvswitch.org
> Cc: Kevin Traynor <ktraynor at redhat.com>; Aaron Conole <aconole at redhat.com>;
> Darrell Ball <dlu998 at gmail.com>
> Subject: RE: [PATCH v6 1/5] netdev-dpdk: fix management of pre-existing
> mempools.
> 
> >From: Fischetti, Antonio
> >Sent: Monday, October 16, 2017 2:15 PM
> >To: dev at openvswitch.org
> >Cc: Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Kevin Traynor
> ><ktraynor at redhat.com>; Aaron Conole <aconole at redhat.com>; Darrell Ball
> ><dlu998 at gmail.com>; Fischetti, Antonio <antonio.fischetti at intel.com>
> >Subject: [PATCH v6 1/5] netdev-dpdk: fix management of pre-existing mempools.
> >
> >Fix issues on reconfiguration of pre-existing mempools.
> >This patch avoids to call dpdk_mp_put() - and erroneously
> >release the mempool - when it already exists.
> >Create mempool names by considering also the NUMA socket number.
> >So a name reflects what socket the mempool is allocated on.
> >This change is needed for the NUMA-awareness feature.
> 
> Hi Antonio,
> 
> Is there any particular reason why you've combined patches 1 and 2 of the
> previous series in a single patch here?
> 
> I would have thought that these two separate issues would warrant two
> individual patches (particularly with respect to the reported-by, tested-by
> tags).

[Antonio]
I guess I misunderstood your previous review where you asked to squash patches 
1 and 3 into one patch.
I understood instead to squash the first 2 patches because they were both bug-fixes.
In the next version v7 I'll restore the 2 separate patches.

> 
> Maybe it's not a big deal, but noted here nonetheless.
> 
> Apart from that, there are some comments inline.
> 
> Thanks again,
> Mark
> 
> >
> >CC: Mark B Kavanagh <mark.b.kavanagh at intel.com>
> >CC: Kevin Traynor <ktraynor at redhat.com>
> >CC: Aaron Conole <aconole at redhat.com>
> >CC: Darrell Ball <dlu998 at gmail.com>
> >Reported-by: Ciara Loftus <ciara.loftus at intel.com>
> >Tested-by: Ciara Loftus <ciara.loftus at intel.com>
> >Reported-by: Róbert Mulik <robert.mulik at ericsson.com>
> >Fixes: d555d9bded5f ("netdev-dpdk: Create separate memory pool for each
> >port.")
> >Signed-off-by: Antonio Fischetti <antonio.fischetti at intel.com>
> >---
> > Test on releasing pre-existing mempools
> > =======================================
> >I've tested this patch by
> >  - changing at run-time the number of Rx queues:
> >      ovs-vsctl set Interface dpdk0 type=dpdk options:n_rxq=4
> >
> >  - reducing the MTU of the dpdk ports of 1 byte to force
> >    the configuration of an existing mempool:
> >      ovs-vsctl set Interface dpdk0 mtu_request=1499
> >
> >This issue was observed in a PVP test topology with dpdkvhostuserclient
> >ports. It can happen also with dpdk type ports, eg by reducing the MTU
> >of 1 byte.
> >
> >To replicate the bug scenario in the PVP case it's sufficient to
> >set 1 dpdkvhostuserclient port, and just boot the VM.
> >
> >Below some more details on my own test setup.
> >
> > PVP test setup
> > --------------
> >CLIENT_SOCK_DIR=/tmp
> >SOCK0=dpdkvhostuser0
> >SOCK1=dpdkvhostuser1
> >
> >1 PMD
> >Add 2 dpdk ports, n_rxq=1
> >Add 2 vhu ports both of type dpdkvhostuserclient and specify vhost-server-path
> > ovs-vsctl set Interface dpdkvhostuser0 options:vhost-server-
> >path="$CLIENT_SOCK_DIR/$SOCK0"
> > ovs-vsctl set Interface dpdkvhostuser1 options:vhost-server-
> >path="$CLIENT_SOCK_DIR/$SOCK1"
> >
> >Set port-based rules: dpdk0 <--> vhu0 and dpdk1 <--> vhu1
> > add-flow br0 in_port=1,action=output:3
> > add-flow br0 in_port=3,action=output:1
> > add-flow br0 in_port=4,action=output:2
> > add-flow br0 in_port=2,action=output:4
> >
> > Launch QEMU
> > -----------
> >As OvS vhu ports are acting as clients, we must specify 'server' in the next
> >command.
> >VM_IMAGE=<path/to/your/vm/image>
> >
> > sudo -E taskset 0x3F00 $QEMU_DIR/x86_64-softmmu/qemu-system-x86_64 -name us-
> >vhost-vm1 -cpu host -enable-kvm -m 4096M -object memory-backend-
> >file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on -numa node,memdev=mem
> >-mem-prealloc -smp 4 -drive file=$VM_IMAGE -chardev
> >socket,id=char0,path=$CLIENT_SOCK_DIR/$SOCK0,server -netdev type=vhost-
> >user,id=mynet1,chardev=char0,vhostforce -device virtio-net-
> >pci,mac=00:00:00:00:00:01,netdev=mynet1,mrg_rxbuf=off -chardev
> >socket,id=char1,path=$CLIENT_SOCK_DIR/$SOCK1,server -netdev type=vhost-
> >user,id=mynet2,chardev=char1,vhostforce -device virtio-net-
> >pci,mac=00:00:00:00:00:02,netdev=mynet2,mrg_rxbuf=off --nographic
> >
> > Expected behavior
> > -----------------
> >With this fix OvS shouldn't crash.
> >
> > Test NUMA-Awareness feature
> > ===========================
> >Mempool names now contains the requested socket id and become like:
> >"ovs_4adb057e_1_2030_20512".
> >
> >Tested with DPDK 17.05.2 (from dpdk-stable branch).
> >NUMA-awareness feature enabled (DPDK/config/common_base).
> >
> >Created 1 single dpdkvhostuser port type.
> >OvS pmd-cpu-mask=FF00003     # enable cores on both numa nodes
> >QEMU core mask = 0xFC000     # cores for qemu on numa node 1 only
> >
> > Before launching the VM:
> > ------------------------
> >ovs-appctl dpif-netdev/pmd-rxq-show
> >shows core #1 is serving the vhu port.
> >
> >pmd thread numa_id 0 core_id 1:
> >        isolated : false
> >        port: dpdkvhostuser0    queue-id: 0
> >
> > After launching the VM:
> > -----------------------
> >the vhu port is now managed by core #27
> >pmd thread numa_id 1 core_id 27:
> >        isolated : false
> >        port: dpdkvhostuser0    queue-id: 0
> >
> >and the log shows a new mempool is allocated on NUMA node 1, while
> >the previous one is deleted:
> >
> >2017-10-06T14:04:55Z|00105|netdev_dpdk|DBG|Allocated
> >"ovs_4adb057e_1_2030_20512" mempool with 20512 mbufs
> >2017-10-06T14:04:55Z|00106|netdev_dpdk|DBG|Releasing
> >"ovs_4adb057e_0_2030_20512" mempool
> >---
> > lib/netdev-dpdk.c | 42 +++++++++++++++++++++++++-----------------
> > 1 file changed, 25 insertions(+), 17 deletions(-)
> >
> >diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> >index c60f46f..7f2d7ed 100644
> >--- a/lib/netdev-dpdk.c
> >+++ b/lib/netdev-dpdk.c
> >@@ -499,8 +499,8 @@ dpdk_mp_name(struct dpdk_mp *dmp)
> > {
> >     uint32_t h = hash_string(dmp->if_name, 0);
> >     char *mp_name = xcalloc(RTE_MEMPOOL_NAMESIZE, sizeof *mp_name);
> >-    int ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE, "ovs_%x_%d_%u",
> >-                       h, dmp->mtu, dmp->mp_size);
> >+    int ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE, "ovs_%x_%d_%d_%u",
> >+                       h, dmp->socket_id, dmp->mtu, dmp->mp_size);
> >     if (ret < 0 || ret >= RTE_MEMPOOL_NAMESIZE) {
> >         return NULL;
> >     }
> >@@ -508,12 +508,13 @@ dpdk_mp_name(struct dpdk_mp *dmp)
> > }
> >
> > static struct dpdk_mp *
> >-dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> >+dpdk_mp_create(struct netdev_dpdk *dev, int mtu, bool *mp_exists)
> > {
> >     struct dpdk_mp *dmp = dpdk_rte_mzalloc(sizeof *dmp);
> >     if (!dmp) {
> >         return NULL;
> >     }
> >+    *mp_exists = false;
> >     dmp->socket_id = dev->requested_socket_id;
> >     dmp->mtu = mtu;
> >     ovs_strzcpy(dmp->if_name, dev->up.name, IFNAMSIZ);
> >@@ -530,15 +531,14 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> >             + MIN(RTE_MAX_LCORE, dev->requested_n_rxq) * NETDEV_MAX_BURST
> >             + MIN_NB_MBUF;
> >
> >-    bool mp_exists = false;
> >-
> >     do {
> >         char *mp_name = dpdk_mp_name(dmp);
> >
> >         VLOG_DBG("Requesting a mempool of %u mbufs for netdev %s "
> >-                 "with %d Rx and %d Tx queues.",
> >+                 "with %d Rx and %d Tx queues, socket id:%d.",
> >                  dmp->mp_size, dev->up.name,
> >-                 dev->requested_n_rxq, dev->requested_n_txq);
> >+                 dev->requested_n_rxq, dev->requested_n_txq,
> >+                 dev->requested_socket_id);
> >
> >         dmp->mp = rte_pktmbuf_pool_create(mp_name, dmp->mp_size,
> >                                           MP_CACHE_SZ,
> >@@ -559,7 +559,7 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> >             /* As the mempool create returned EEXIST we can expect the
> >              * lookup has returned a valid pointer.  If for some reason
> >              * that's not the case we keep track of it. */
> >-            mp_exists = true;
> >+            *mp_exists = true;
> >         } else {
> >             VLOG_ERR("Failed mempool \"%s\" create request of %u mbufs",
> >                      mp_name, dmp->mp_size);
> >@@ -573,7 +573,7 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> >             rte_mempool_obj_iter(dmp->mp, ovs_rte_pktmbuf_init, NULL);
> >             return dmp;
> >         }
> >-    } while (!mp_exists &&
> >+    } while (!(*mp_exists) &&
> >             (rte_errno == ENOMEM && (dmp->mp_size /= 2) >= MIN_NB_MBUF));
> >
> >     rte_free(dmp);
> >@@ -581,12 +581,12 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> > }
> >
> > static struct dpdk_mp *
> >-dpdk_mp_get(struct netdev_dpdk *dev, int mtu)
> >+dpdk_mp_get(struct netdev_dpdk *dev, int mtu, bool *mp_exists)
> > {
> >     struct dpdk_mp *dmp;
> >
> >     ovs_mutex_lock(&dpdk_mp_mutex);
> >-    dmp = dpdk_mp_create(dev, mtu);
> >+    dmp = dpdk_mp_create(dev, mtu, mp_exists);
> >     ovs_mutex_unlock(&dpdk_mp_mutex);
> >
> >     return dmp;
> >@@ -620,14 +620,22 @@ netdev_dpdk_mempool_configure(struct netdev_dpdk *dev)
> 
> Apologies for not noticing this in my previous review, but the comment for this
> function needs to be updated.
> 
> It currently reads:
>    " /* Tries to allocate new mempool on requested_socket_id with
> 	 * mbuf size corresponding to requested_mtu.
> 	 * On success new configuration will be applied.
> 	 * On error, device will be left unchanged. */"
> 
> It should be updated to reflect the fact that it tries to allocate a new
> mempool, or reuse an existing one, where appropriate.
> Furthermore, if the error value is EEXIST, the new configuration (i.e. dev-
> >mtu, dev->max_packet_len) is applied, so the device is not unchanged, as the
> comment suggests.

[Antonio] Thanks, I'll change that.


> 
> > {
> >     uint32_t buf_size = dpdk_buf_size(dev->requested_mtu);
> >     struct dpdk_mp *mp;
> >+    bool mp_exists;
> 
> You don't need the 'mp_exists' variable.
> 
> If, as part of the dpdk_mp_get() call stack, rte_mempool_lookup() fails, then
> dpdk_mp_create() returns NULL, which is already handled by
> netdev_dpdk_mempool_configure(),
> (marked as [1], below).

[Antonio]
If rte_mempool_lookup() fails a NULL is returned but rte_errno == ENOENT, so it's no more EEXIST.
This means that in netdev_dpdk_mempool_configure() I should check both error codes like:
if (rte_errno == EEXIST || rte_errno == ENOENT)
moreover who knows if in the future the rte_mempool_lookup() will be enriched to return
even more error codes?
Also, I think it's good to rely on rte_errno as long as you test it immediately, I mean 
right after the API call. In the case of netdev_dpdk_mempool_configure() the rte_errno 
was updated by dpdk_mp_create(), which is 2 levels below in the call stack.
That's why I'd prefer to keep track that we are re-using a mempool into an OVS variable 
and be less dependent by RTE return codes.

BTW I could have added mp_exists variable into struct dpdk_mp but I avoided that because 
that goes inside struct netdev_dpdk and I didn't want to increase its size. So I preferred 
to add it as a new input parameter for the functions.

> 
> So, to handle the case where the mempool already exists - i.e. when in the
> callstack, rte_pkt_mbuf_pool_create() failed and set rte_errno to EEXIST - you
> only need to check rte_errno here;
> (see [2], below).
> 
> >
> >-    mp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size));
> >+    mp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size), &mp_exists);
> 
> [1]
> >     if (!mp) {
> >         VLOG_ERR("Failed to create memory pool for netdev "
> >                  "%s, with MTU %d on socket %d: %s\n",
> >                  dev->up.name, dev->requested_mtu, dev->requested_socket_id,
> >                  rte_strerror(rte_errno));
> >         return rte_errno;
> >+    } else if (mp_exists) {
> 
> [2]
> "if (rte_errno == EEXIST)" is sufficient here
> 
> >+        /* If a new MTU was requested and its rounded value equals the one
> >+         * that is currently used, then the existing mempool is returned.
> >+         * Update dev with the new values. */
> >+        dev->mtu = dev->requested_mtu;
> >+        dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu);
> >+        return EEXIST;
> 
> Replace with "return rte_errno" for consistency with the previous return (since
> the value of rte_errno is guaranteed to be EEXIST here).

[Antonio]
All the callers - like dpdk_vhost_reconfigure_helper() - behave depending on the
outcome of rte_pktmbuf_pool_create(), that could return an error for insufficient
memory for example.
That's why in the previous return I'm returning rte_errno as it is. Instead here
I'm overriding what could be returned by rte_mempool_lookup() and returning EEXIST
because that's the information we want to report to the caller.

 
> 
> >     } else {
> >         dpdk_mp_put(dev->dpdk_mp);
> >         dev->dpdk_mp = mp;
> >@@ -3207,7 +3215,7 @@ netdev_dpdk_reconfigure(struct netdev *netdev)
> >     rte_eth_dev_stop(dev->port_id);
> >
> >     err = netdev_dpdk_mempool_configure(dev);
> >-    if (err) {
> >+    if (err && err != EEXIST) {
> >         goto out;
> >     }
> >
> >@@ -3247,12 +3255,12 @@ dpdk_vhost_reconfigure_helper(struct netdev_dpdk *dev)
> >     netdev_dpdk_remap_txqs(dev);
> >
> >     err = netdev_dpdk_mempool_configure(dev);
> >-    if (err) {
> >-        return err;
> >-    } else {
> >+    if (!err) {
> >+        /* A new mempool was created. */
> >         netdev_change_seq_changed(&dev->up);
> >+    } else if (err != EEXIST){
> >+        return err;
> >     }
> >-
> >     if (netdev_dpdk_get_vid(dev) >= 0) {
> >         if (dev->vhost_reconfigured == false) {
> >             dev->vhost_reconfigured = true;
> >--
> >2.4.11



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