[Kernel-packages] [Bug 1692538] Comment bridged from LTC Bugzilla

2017-11-20 Thread bugproxy 
--- Comment From sikri...@in.ibm.com 2017-11-21 02:33 EDT---
Hi Daniel,

Yes. I meant TCP Segmentation Offload when I said large-send offload.

Your understanding of the current ibmveth code is right.

AIX Path MTU Discovery is enabled by default and so though the very
first packet (larger payload) can leave the LPAR with higher MSS, AIX
will discover that the path MTU size is lower than the MSS negotiated.
This leads to AIX TCP recovering (based on path MTU values) and sending
packets of right MTU size for further packets.

But if user disables Path MTU and configures an MTU higher than what
physical NIC can support, then this will lead to packet drops (and AIX
stack cannot rediscover MTU without path MTU). So, second scenario you
mentioned in your note will lead to communication issues.

Also by default, AIX MTU settings are optimal ones i.e 1500 bytes (even
when TSO is enabled). This helps in AIX LPAR sending larger payloads
with MSS value of 1500. If an user knows that the physical NIC in VIOS
or Linux IO server has Jumbo frames enabled, MTU can be set to 9000
(here again if TSO is enabled, larger payloads will go with MSS of
9000).  So, the optimal values are the default values (1500/9000).

Regards,
Siva K.

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Title:
  Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA

Status in The Ubuntu-power-systems project:
  In Progress
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Zesty:
  Fix Released
Status in linux source package in Artful:
  Fix Released

Bug description:
  
  == SRU Justification ==
  Commit 66aa0678ef is request to fix four issues with the ibmveth driver.
  The issues are as follows:
  - Issue 1: ibmveth doesn't support largesend and checksum offload features 
when configured as "Trunk".
  - Issue 2: SYN packet drops seen at destination VM. When the packet
  originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to IO
  server's inbound Trunk ibmveth, on validating "checksum good" bits in ibmveth
  receive routine, SKB's ip_summed field is set with CHECKSUM_UNNECESSARY flag.
  - Issue 3: First packet of a TCP connection will be dropped, if there is
  no OVS flow cached in datapath.
  - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.

  The details for the fixes to these issues are described in the commits
  git log.



  == Comment: #0 - BRYANT G. LY  - 2017-05-22 08:40:16 ==
  ---Problem Description---

   - Issue 1: ibmveth doesn't support largesend and checksum offload features
     when configured as "Trunk". Driver has explicit checks to prevent
     enabling these offloads.

   - Issue 2: SYN packet drops seen at destination VM. When the packet
     originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to
     IO server's inbound Trunk ibmveth, on validating "checksum good" bits
     in ibmveth receive routine, SKB's ip_summed field is set with
     CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux
     Bridge) and delivered to outbound Trunk ibmveth. At this point the
     outbound ibmveth transmit routine will not set "no checksum" and
     "checksum good" bits in transmit buffer descriptor, as it does so only
     when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets
     delivered to destination VM, TCP layer receives the packet with checksum
     value of 0 and with no checksum related flags in ip_summed field. This
     leads to packet drops. So, TCP connections never goes through fine.

   - Issue 3: First packet of a TCP connection will be dropped, if there is
     no OVS flow cached in datapath. OVS while trying to identify the flow,
     computes the checksum. The computed checksum will be invalid at the
     receiving end, as ibmveth transmit routine zeroes out the pseudo
     checksum value in the packet. This leads to packet drop.

   - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.
     When Physical NIC has GRO enabled and when OVS bridges these packets,
     OVS vport send code will end up calling dev_queue_xmit, which in turn
     calls validate_xmit_skb.
     In validate_xmit_skb routine, the larger packets will get segmented into
     MSS sized segments, if SKB has a frag_list and if the driver to which
     they are delivered to doesn't support NETIF_F_FRAGLIST feature.

  Contact Information = Bryant G. Ly/b...@us.ibm.com

  ---uname output---
  4.8.0-51.54

  Machine Type = p8

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
   Increases performance greatly

  The patch has been accepted upstream:
  https://patchwork.ozlabs.org/patch/764533/

To manage notifications about this bug go to:

[Kernel-packages] [Bug 1692538] Comment bridged from LTC Bugzilla

2017-11-20 Thread bugproxy 
--- Comment From sikri...@in.ibm.com 2017-11-20 04:13 EDT---
Hi Daniel,

When one enables largesend offload in AIX, MTU still stays at 1500 (when
Jumbo frames are disabled) and 9000 (when Jumbo frames are enabled). So,
when a workload pushes data > MTU sizes, AIX LPAR will send the bigger
payload with an MSS value based on MTU. This MSS value is what the
adapter uses later for segmenting.

By default AIX doesn't set MTU to 64k when largesend is enabled. In the
scenario described in bnx2x driver issue, I suspect the end-user
manually changed the MTU to a bigger value (~64k or so), otherwise we
shouldn't be seeing this issue.

Now, coming back to your question on what will happen if user configures
a bigger MTU value (say for example 64k), AIX LPAR will send the bigger
payload to VIOS with MSS value ~64k, this will lead to physical NICs in
VIOS drop the packet, leading to restransmissions from AIX LPAR.
Eventually AIX LPAR will disable largesend offload for the specific
connection, post certain number of retransmissions and then the data
flow goes through fine. So, in the event of user misconfiguration, I
agree there will be a performance impact.

This issue may happen in non-virtualized environment too, when the end-
user sets a higher MTU than the one supported by the physical adapter.
Here the driver/adapter may drop the packet, leading to retransmissions.

Regards,
Siva K

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https://bugs.launchpad.net/bugs/1692538

Title:
  Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA

Status in The Ubuntu-power-systems project:
  In Progress
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Zesty:
  Fix Released
Status in linux source package in Artful:
  Fix Released

Bug description:
  
  == SRU Justification ==
  Commit 66aa0678ef is request to fix four issues with the ibmveth driver.
  The issues are as follows:
  - Issue 1: ibmveth doesn't support largesend and checksum offload features 
when configured as "Trunk".
  - Issue 2: SYN packet drops seen at destination VM. When the packet
  originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to IO
  server's inbound Trunk ibmveth, on validating "checksum good" bits in ibmveth
  receive routine, SKB's ip_summed field is set with CHECKSUM_UNNECESSARY flag.
  - Issue 3: First packet of a TCP connection will be dropped, if there is
  no OVS flow cached in datapath.
  - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.

  The details for the fixes to these issues are described in the commits
  git log.



  == Comment: #0 - BRYANT G. LY  - 2017-05-22 08:40:16 ==
  ---Problem Description---

   - Issue 1: ibmveth doesn't support largesend and checksum offload features
     when configured as "Trunk". Driver has explicit checks to prevent
     enabling these offloads.

   - Issue 2: SYN packet drops seen at destination VM. When the packet
     originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to
     IO server's inbound Trunk ibmveth, on validating "checksum good" bits
     in ibmveth receive routine, SKB's ip_summed field is set with
     CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux
     Bridge) and delivered to outbound Trunk ibmveth. At this point the
     outbound ibmveth transmit routine will not set "no checksum" and
     "checksum good" bits in transmit buffer descriptor, as it does so only
     when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets
     delivered to destination VM, TCP layer receives the packet with checksum
     value of 0 and with no checksum related flags in ip_summed field. This
     leads to packet drops. So, TCP connections never goes through fine.

   - Issue 3: First packet of a TCP connection will be dropped, if there is
     no OVS flow cached in datapath. OVS while trying to identify the flow,
     computes the checksum. The computed checksum will be invalid at the
     receiving end, as ibmveth transmit routine zeroes out the pseudo
     checksum value in the packet. This leads to packet drop.

   - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.
     When Physical NIC has GRO enabled and when OVS bridges these packets,
     OVS vport send code will end up calling dev_queue_xmit, which in turn
     calls validate_xmit_skb.
     In validate_xmit_skb routine, the larger packets will get segmented into
     MSS sized segments, if SKB has a frag_list and if the driver to which
     they are delivered to doesn't support NETIF_F_FRAGLIST feature.

  Contact Information = Bryant G. Ly/b...@us.ibm.com

  ---uname output---
  4.8.0-51.54

  Machine Type = p8

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
   Increases performance greatly

  The

[Kernel-packages] [Bug 1692538] Comment bridged from LTC Bugzilla

2017-11-17 Thread bugproxy 
--- Comment From b...@us.ibm.com 2017-11-17 11:07 EDT---
I was told that this issue is due to a mis-configuration where if end to end 
MTU isn't set correctly then you will see this problem. So as long as the user 
sets the MTU end to end correctly you shouldn't see this problem.

-- 
You received this bug notification because you are a member of Kernel
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https://bugs.launchpad.net/bugs/1692538

Title:
  Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA

Status in The Ubuntu-power-systems project:
  In Progress
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Zesty:
  Fix Released
Status in linux source package in Artful:
  Fix Released

Bug description:
  
  == SRU Justification ==
  Commit 66aa0678ef is request to fix four issues with the ibmveth driver.
  The issues are as follows:
  - Issue 1: ibmveth doesn't support largesend and checksum offload features 
when configured as "Trunk".
  - Issue 2: SYN packet drops seen at destination VM. When the packet
  originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to IO
  server's inbound Trunk ibmveth, on validating "checksum good" bits in ibmveth
  receive routine, SKB's ip_summed field is set with CHECKSUM_UNNECESSARY flag.
  - Issue 3: First packet of a TCP connection will be dropped, if there is
  no OVS flow cached in datapath.
  - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.

  The details for the fixes to these issues are described in the commits
  git log.



  == Comment: #0 - BRYANT G. LY  - 2017-05-22 08:40:16 ==
  ---Problem Description---

   - Issue 1: ibmveth doesn't support largesend and checksum offload features
     when configured as "Trunk". Driver has explicit checks to prevent
     enabling these offloads.

   - Issue 2: SYN packet drops seen at destination VM. When the packet
     originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to
     IO server's inbound Trunk ibmveth, on validating "checksum good" bits
     in ibmveth receive routine, SKB's ip_summed field is set with
     CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux
     Bridge) and delivered to outbound Trunk ibmveth. At this point the
     outbound ibmveth transmit routine will not set "no checksum" and
     "checksum good" bits in transmit buffer descriptor, as it does so only
     when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets
     delivered to destination VM, TCP layer receives the packet with checksum
     value of 0 and with no checksum related flags in ip_summed field. This
     leads to packet drops. So, TCP connections never goes through fine.

   - Issue 3: First packet of a TCP connection will be dropped, if there is
     no OVS flow cached in datapath. OVS while trying to identify the flow,
     computes the checksum. The computed checksum will be invalid at the
     receiving end, as ibmveth transmit routine zeroes out the pseudo
     checksum value in the packet. This leads to packet drop.

   - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.
     When Physical NIC has GRO enabled and when OVS bridges these packets,
     OVS vport send code will end up calling dev_queue_xmit, which in turn
     calls validate_xmit_skb.
     In validate_xmit_skb routine, the larger packets will get segmented into
     MSS sized segments, if SKB has a frag_list and if the driver to which
     they are delivered to doesn't support NETIF_F_FRAGLIST feature.

  Contact Information = Bryant G. Ly/b...@us.ibm.com

  ---uname output---
  4.8.0-51.54

  Machine Type = p8

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
   Increases performance greatly

  The patch has been accepted upstream:
  https://patchwork.ozlabs.org/patch/764533/

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-power-systems/+bug/1692538/+subscriptions

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[Kernel-packages] [Bug 1692538] Comment bridged from LTC Bugzilla

2017-11-13 Thread bugproxy 
--- Comment From b...@us.ibm.com 2017-11-13 09:53 EDT---
Tested on Xenial, looks good.

-- 
You received this bug notification because you are a member of Kernel
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https://bugs.launchpad.net/bugs/1692538

Title:
  Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA

Status in The Ubuntu-power-systems project:
  In Progress
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Zesty:
  Fix Released
Status in linux source package in Artful:
  Fix Released

Bug description:
  
  == SRU Justification ==
  Commit 66aa0678ef is request to fix four issues with the ibmveth driver.
  The issues are as follows:
  - Issue 1: ibmveth doesn't support largesend and checksum offload features 
when configured as "Trunk".
  - Issue 2: SYN packet drops seen at destination VM. When the packet
  originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to IO
  server's inbound Trunk ibmveth, on validating "checksum good" bits in ibmveth
  receive routine, SKB's ip_summed field is set with CHECKSUM_UNNECESSARY flag.
  - Issue 3: First packet of a TCP connection will be dropped, if there is
  no OVS flow cached in datapath.
  - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.

  The details for the fixes to these issues are described in the commits
  git log.



  == Comment: #0 - BRYANT G. LY  - 2017-05-22 08:40:16 ==
  ---Problem Description---

   - Issue 1: ibmveth doesn't support largesend and checksum offload features
     when configured as "Trunk". Driver has explicit checks to prevent
     enabling these offloads.

   - Issue 2: SYN packet drops seen at destination VM. When the packet
     originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to
     IO server's inbound Trunk ibmveth, on validating "checksum good" bits
     in ibmveth receive routine, SKB's ip_summed field is set with
     CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux
     Bridge) and delivered to outbound Trunk ibmveth. At this point the
     outbound ibmveth transmit routine will not set "no checksum" and
     "checksum good" bits in transmit buffer descriptor, as it does so only
     when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets
     delivered to destination VM, TCP layer receives the packet with checksum
     value of 0 and with no checksum related flags in ip_summed field. This
     leads to packet drops. So, TCP connections never goes through fine.

   - Issue 3: First packet of a TCP connection will be dropped, if there is
     no OVS flow cached in datapath. OVS while trying to identify the flow,
     computes the checksum. The computed checksum will be invalid at the
     receiving end, as ibmveth transmit routine zeroes out the pseudo
     checksum value in the packet. This leads to packet drop.

   - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.
     When Physical NIC has GRO enabled and when OVS bridges these packets,
     OVS vport send code will end up calling dev_queue_xmit, which in turn
     calls validate_xmit_skb.
     In validate_xmit_skb routine, the larger packets will get segmented into
     MSS sized segments, if SKB has a frag_list and if the driver to which
     they are delivered to doesn't support NETIF_F_FRAGLIST feature.

  Contact Information = Bryant G. Ly/b...@us.ibm.com

  ---uname output---
  4.8.0-51.54

  Machine Type = p8

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
   Increases performance greatly

  The patch has been accepted upstream:
  https://patchwork.ozlabs.org/patch/764533/

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-power-systems/+bug/1692538/+subscriptions

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[Kernel-packages] [Bug 1692538] Comment bridged from LTC Bugzilla

2017-07-25 Thread bugproxy 
--- Comment From b...@us.ibm.com 2017-07-25 14:52 EDT---
It looks like the directory had artful and zesty. I didnt see anything in 
Xenial but Zesty/Artful works.

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https://bugs.launchpad.net/bugs/1692538

Title:
  Ubuntu 16.04.02: ibmveth: Support to enable LSO/CSO for Trunk VEA

Status in The Ubuntu-power-systems project:
  Confirmed
Status in linux package in Ubuntu:
  Confirmed

Bug description:
  == Comment: #0 - BRYANT G. LY  - 2017-05-22 08:40:16 ==
  ---Problem Description---

   - Issue 1: ibmveth doesn't support largesend and checksum offload features
 when configured as "Trunk". Driver has explicit checks to prevent
 enabling these offloads.

   - Issue 2: SYN packet drops seen at destination VM. When the packet
 originates, it has CHECKSUM_PARTIAL flag set and as it gets delivered to
 IO server's inbound Trunk ibmveth, on validating "checksum good" bits
 in ibmveth receive routine, SKB's ip_summed field is set with
 CHECKSUM_UNNECESSARY flag. This packet is then bridged by OVS (or Linux
 Bridge) and delivered to outbound Trunk ibmveth. At this point the
 outbound ibmveth transmit routine will not set "no checksum" and
 "checksum good" bits in transmit buffer descriptor, as it does so only
 when the ip_summed field is CHECKSUM_PARTIAL. When this packet gets
 delivered to destination VM, TCP layer receives the packet with checksum
 value of 0 and with no checksum related flags in ip_summed field. This
 leads to packet drops. So, TCP connections never goes through fine.

   - Issue 3: First packet of a TCP connection will be dropped, if there is
 no OVS flow cached in datapath. OVS while trying to identify the flow,
 computes the checksum. The computed checksum will be invalid at the
 receiving end, as ibmveth transmit routine zeroes out the pseudo
 checksum value in the packet. This leads to packet drop.

   - Issue 4: ibmveth driver doesn't have support for SKB's with frag_list.
 When Physical NIC has GRO enabled and when OVS bridges these packets,
 OVS vport send code will end up calling dev_queue_xmit, which in turn
 calls validate_xmit_skb.
 In validate_xmit_skb routine, the larger packets will get segmented into
 MSS sized segments, if SKB has a frag_list and if the driver to which
 they are delivered to doesn't support NETIF_F_FRAGLIST feature.
   
  Contact Information = Bryant G. Ly/b...@us.ibm.com 
   
  ---uname output---
  4.8.0-51.54
   
  Machine Type = p8 
   
  ---Debugger---
  A debugger is not configured
   
  ---Steps to Reproduce---
   Increases performance greatly

  The patch has been accepted upstream: 
  https://patchwork.ozlabs.org/patch/764533/

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-power-systems/+bug/1692538/+subscriptions

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