1. 13 Jan, 2015 39 commits
  2. 12 Jan, 2015 1 commit
    • David S. Miller's avatar
      Merge branch 'tuntap_queues' · d2c60b13
      David S. Miller authored
      Pankaj Gupta says:
      
      ====================
      Increase the limit of tuntap queues
      
      Networking under KVM works best if we allocate a per-vCPU rx and tx
      queue in a virtual NIC. This requires a per-vCPU queue on the host side.
      Modern physical NICs have multiqueue support for large number of queues.
      To scale vNIC to run multiple queues parallel to maximum number of vCPU's
      we need to increase number of queues support in tuntap.
      
      Changes from v4:
      PATCH2: Michael.S.Tsirkin - Updated change comment message.
      
      Changes from v3:
      PATCH1: Michael.S.Tsirkin - Some cleanups and updated commit message.
                                  Perf numbers on 10 Gbs NIC
      Changes from v2:
      PATCH 3: David Miller     - flex array adds extra level of indirection
                                  for preallocated array.(dropped, as flow array
      			    is allocated using kzalloc with failover to zalloc).
      Changes from v1:
      PATCH 2: David Miller     - sysctl changes to limit number of queues
                                  not required for unprivileged users(dropped).
      
      Changes from RFC
      PATCH 1: Sergei Shtylyov  - Add an empty line after declarations.
      PATCH 2: Jiri Pirko -       Do not introduce new module paramaters.
      	 Michael.S.Tsirkin- We can use sysctl for limiting max number
                                  of queues.
      
      This series is to increase the number of tuntap queues. Original work is being
      done by 'jasowang@redhat.com'. I am taking this 'https://lkml.org/lkml/2013/6/19/29'
      patch series as a reference. As per discussion in the patch series:
      
      There were two reasons which prevented us from increasing number of tun queues:
      
      - The netdev_queue array in netdevice were allocated through kmalloc, which may
        cause a high order memory allocation too when we have several queues.
        E.g. sizeof(netdev_queue) is 320, which means a high order allocation would
        happens when the device has more than 16 queues.
      
      - We store the hash buckets in tun_struct which results a very large size of
        tun_struct, this high order memory allocation fail easily when the memory is
        fragmented.
      
      The patch 60877a32
      
       increases the number of tx
      queues. Memory allocation fallback to vzalloc() when kmalloc() fails.
      
      This series tries to address following issues:
      
      - Increase the number of netdev_queue queues for rx similarly its done for tx
        queues by falling back to vzalloc() when memory allocation with kmalloc() fails.
      
      - Increase number of queues to 256, maximum number is equal to maximum number
        of vCPUS allowed in a guest.
      
      I have also done testing with multiple parallel Netperf sessions for different
      combination of queues and CPU's. It seems to be working fine without much increase
      in cpu load with increase in number of queues. I also see good increase in throughput
      with increase in number of queues. Though i had limitation of 8 physical CPU's.
      
      For this test: Two Hosts(Host1 & Host2) are directly connected with cable
      Host1 is running Guest1. Data is sent from Host2 to Guest1 via Host1.
      
      Host kernel: 3.19.0-rc2+, AMD Opteron(tm) Processor 6320
      NIC : Emulex Corporation OneConnect 10Gb NIC (be3)
      
      Patch Applied  %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle  throughput
      Single Queue, 2 vCPU's
      -------------
      Before Patch :all    0.19    0.00    0.16    0.07    0.04    0.10    0.00    0.18    0.00   99.26  57864.18
      After  Patch :all    0.99    0.00    0.64    0.69    0.07    0.26    0.00    1.58    0.00   95.77  57735.77
      
      With 2 Queues, 2 vCPU's
      ---------------
      Before Patch :all    0.19    0.00    0.19    0.10    0.04    0.11    0.00    0.28    0.00   99.08  63083.09
      After  Patch :all    0.87    0.00    0.73    0.78    0.09    0.35    0.00    2.04    0.00   95.14  62917.03
      
      With 4 Queues, 4 vCPU's
      --------------
      Before Patch :all    0.20    0.00    0.21    0.11    0.04    0.12    0.00    0.32    0.00   99.00  80865.06
      After  Patch :all    0.71    0.00    0.93    0.85    0.11    0.51    0.00    2.62    0.00   94.27  86463.19
      
      With 8 Queues, 8 vCPU's
      --------------
      Before Patch :all    0.19    0.00    0.18    0.09    0.04    0.11    0.00    0.23    0.00   99.17  86795.31
      After  Patch :all    0.65    0.00    1.18    0.93    0.13    0.68    0.00    3.38    0.00   93.05  89459.93
      
      With 16 Queues, 8 vCPU's
      --------------
      After  Patch :all    0.61    0.00    1.59    0.97    0.18    0.92    0.00    4.32    0.00   91.41  120951.60
      ====================
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      d2c60b13