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

Fischetti, Antonio antonio.fischetti at intel.com
Wed Oct 18 09:43:00 UTC 2017



> -----Original Message-----
> From: Kavanagh, Mark B
> Sent: Tuesday, October 17, 2017 10:14 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: Tuesday, October 17, 2017 6:04 PM
> >To: Kavanagh, Mark B <mark.b.kavanagh 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.
> >
> >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.
> 
> Hi Antonio,
> 
> I figured as much ;)
> 
> >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.
> 
> Thanks - I think that's a much cleaner approach.
> 
> >
> >>
> >> 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.
> 
> Yes, agreed.
> 
> >This means that in netdev_dpdk_mempool_configure() I should check both error
> >codes like:
> >if (rte_errno == EEXIST || rte_errno == ENOENT)
> 
> You won't need to do that - hopefully the following will make things clearer.
> 
> Consider the callstack, starting from netdev_dpdk_mempool_configure:

[Antonio] I get your point now. 
Cool, I'll follow your suggestion. 
Thanks for all your explanation!


> 
> [netdev_dpdk_mempool_configure]
>  mp = dpdk_mp_get()
> 
> 	[dpdk_mp_get]
> 	mp = dpdk_mp_create()
> 
> 		[dpdk_mp_create]
> 		dmp->mp = rte_pktmbuf_pool_create(....)
> 		# assume this returns NULL and sets rte_errno to EEXIST,
> 		# as an appropriate mempool already exists
> 
> 			if (dmp->mp) {
> 				# skip
> 			} else if (rte_errno == EEXIST) {
> 				dmp->mp = rte_mempool_lookup(...)
> 				# There are two possible scenarios here -
> 				# let's name them A and B, respectively, and
> follow their paths.
> 
> -------------------------------------------------------------------------------
> -------
> 
> 				### Scenario A - rte_mempool_lookup() returns NULL
> and sets ###
> 				### rte_errno to ENOENT
> ###
> 
> 				mp_exists = true;
>       	     } else {
>            			# skip
> 			}
> 			if (dmp->mp) {
> 				# skip
> 			}
> 		} while (!mp_exists) &&     # condition fails, as mp_exists is
> true
> 		...
> 		return NULL;
> 
> 	[dpdk_mp_get]
> 	return NULL
> 
> [netdev_dpdk_mempool_configure]
> if (!mp) {
> 	VLOG_ERR(...)
> 	return rte_errno        # return ENONENT
> 
> -------------------------------------------------------------------------------
> ------
> 
> 				### Scenario B - rte_mempool_lookup() returns a
> pointer to ###
> 				### the mempool; rte_errno remains set to EEXIST
> ###
> 				mp_exists = true;
>       	     } else {
>            			# skip
> 			}
> 			if (dmp->mp) {
> 				return dmp;   # return a pointer to the mempool
> 			}
> 	[dpdk_mp_get]
> 	return a pointer to the mempool
> 
> [netdev_dpdk_mempool_configure]
> if (!mp) {
> 	# skip
> } else if (rte_errno == EEXIST) {
> 	dev->mtu = dev->requested_mtu;
> 	dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu);
> 	return rte_errno;              # this returns EEXIST
> }
> 
> >moreover who knows if in the future the rte_mempool_lookup() will be enriched
> >to return
> >even more error codes?
> 
> That point is moot IMO, as we should handle the API as it behaves currently,
> and not how it may do so at some potential future date.
> Just my $0.02 ;)
> 
> >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.
> 
> That value is set in the same thread in a defined call-stack; I don't see a
> disadvantage to referencing it here tbh.

[Antonio] ok.


> 
> >
> >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.
> 
> As described previously.

[Antonio] ok.


> 
> Thanks,
> Mark
> 
> >
> >
> >>
> >> >     } 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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