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authorSteven Luong <sluong@cisco.com>2019-02-01 10:23:56 -0800
committerDamjan Marion <dmarion@me.com>2019-02-21 22:03:40 +0000
commit67f935ec6eb9ec37b7d73029c5afa89cbf4a9aa2 (patch)
treef32c614f93d27697115ffd412eeb1c28819ee7ea /README.md
parent3be3cd60bc41d095174ea413aa753a7bd9eff73e (diff)
vhost: VPP stalls with vhost performing control plane actions
Symptom ------- With NDR traffic blasting at VPP, bringing up a new VM with vhost connection to VPP causes packet drops. I am able to recreate this problem easily using a simple setup like this. TREX-------------- switch ---- VPP |---------------| |-------| Cause ----- The reason for the packet drops is due to vhost holding onto the worker barrier lock for too long in vhost_user_socket_read(). There are quite a few of system calls inside the routine. At the end of the routine, it unconditionally calls vhost_user_update_iface_state() for all message types. vhost_user_update_iface_state() also unconditionally calls vhost_user_rx_thread_placement() and vhost_user_tx_thread_placement(). vhost_user_rx_thread_placement scraps out all existing cpu/queue mappings for the interface and creates brand new cpu/queue mappings for the interface. This process is very disruptive and very expensive. In my opinion, this area of code needs a makeover. Fixes ----- * vhost_user_socket_read() is rewritten that it should not hold onto the worker barrier lock for system calls, or at least minimize the need for doing it. * Remove the call to vhost_user_update_iface_state as a default route at the end of vhost_user_socket_read(). There is only a couple of message types which really need to call vhost_user_update_iface_state(). We put the call to those message types which need it. * Remove vhost_user_rx_thread_placement() and vhost_user_tx_thread_placement from vhost_user_update_iface_state(). There is no need to repetatively change the cpu/queue mappings. * vhost_user_rx_thread_placement() is actually quite expensive. It should be called only once per queue for the interface. There is no need to scrap the existing cpu/queue mappings and create new cpu/queue mappings when the additional queues becomes active/enable. * Change to create the cpu/queue mappings for the first RX when the interface is created. Dont remove the cpu/queue mapping when the interface is disconnected. Remove the cpu/queue mapping only when the interface is deleted. The create vhost user interface CLI also has some very expensive system calls if the command is entered with the optional keyword "server" As a bonus, This patch makes the create vhost user interface binary-api and CLI thread safe. Do the protection for the small amount of code which is thread unsafe. Change-Id: I4a19cbf7e9cc37ea01286169882e5603e6d7eb77 Signed-off-by: Steven Luong <sluong@cisco.com>
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