[ofa-general] PCI-Express payload

[Koen Segers]

Hi Dotan,

You are refering to the MTU of InfiniBand. This parameter defines how
much data a single packet can contain when transferred over an
Infiniband network. 

I want to know the MTU of PCI-Express. PCI-Express is used to transfer
data from memory to HCA and vice versa. As far as I know, this MTU can
differ. Our SAS HBA, has a PCI-Express MTU of 512 bytes. 

Regards,

Koen


On Mon, 2008-03-31 at 15:05 +0300, Dotan Barak wrote:
> Hi.
> 
> You can check what is the maximum supported MTU of your HCA using 
> ibv_devinfo.
> Most of the HCAs supports 2KB MTU and some of them 4KB MTU.
> 
> The MTU is the maximum payload size that can be sent/received
> (the space for the IB headers are not part of the MTU)
> 
> 
> Every connected QP (RC/UC) can define which MTU value he is using 
> (according to the
> used path).
> 
> 
> I hope that is the info you asked for ..
> Dotan
> 
> Koen Segers wrote:
> > Hi,
> >
> > I'm interested in computing the overhead coming from PCI-Express to an 
> > IB HCA. Therefore I need to know the payload size of different types 
> > of HCA.
> >
> > We have InfiniHost III Mellanox cards of 4x SDR and DDR IB. According 
> > the lspci -vvv command on SLES 10 SP1, the PCI-e payload of these 
> > cards is maximum 128 bytes.
> >
> > Can someone give my the payload size for a ConnectX 4x SDR and DDR IB 
> > card?
> >
> > Thank you,
> >
> > Koen
> >
> > This is my output:
> > 41:00.0 InfiniBand: Mellanox Technologies MT25208 InfiniHost III Ex 
> > (rev a0)
> >         Subsystem: Mellanox Technologies MT25208 InfiniHost III Ex
> >         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- 
> > ParErr+ Stepping- SERR- FastB2B-
> >         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- 
> > <TAbort- <MAbort- >SERR- <PERR-
> >         Latency: 0, Cache Line Size: 64 bytes
> >         Interrupt: pin A routed to IRQ 209
> >         Region 0: Memory at e1700000 (64-bit, non-prefetchable) [size=1M]
> >         Region 2: Memory at e1800000 (64-bit, prefetchable) [size=8M]
> >         Capabilities: [40] Power Management version 2
> >                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA 
> > PME(D0-,D1-,D2-,D3hot-,D3cold-)
> >                 Status: D0 PME-Enable- DSel=0 DScale=0 PME-
> >         Capabilities: [48] Vital Product Data
> >         Capabilities: [90] Message Signalled Interrupts: Mask- 64bit+ 
> > Queue=0/5 Enable-
> >                 Address: 0000000000000000  Data: 0000
> >         Capabilities: [84] MSI-X: Enable+ Mask- TabSize=32
> >                 Vector table: BAR=0 offset=00082000
> >                 PBA: BAR=0 offset=00082200
> >         Capabilities: [60] Express Endpoint IRQ 0
> > *                Device: Supported: MaxPayload 128 bytes, PhantFunc 0, 
> > ExtTag+*
> >                 Device: Latency L0s <64ns, L1 unlimited
> >                 Device: AtnBtn- AtnInd- PwrInd-
> >                 Device: Errors: Correctable- Non-Fatal+ Fatal+ 
> > Unsupported-
> >                 Device: RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
> >                 Device: MaxPayload 128 bytes, MaxReadReq 4096 bytes
> >                 Link: Supported Speed 2.5Gb/s, Width x8, ASPM L0s, Port 8
> >                 Link: Latency L0s unlimited, L1 unlimited
> >                 Link: ASPM Disabled RCB 128 bytes CommClk- ExtSynch-
> >                 Link: Speed 2.5Gb/s, Width x8
> >
> >  
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*** Disclaimer ***

Vlaamse Radio- en Televisieomroep
Auguste Reyerslaan 52, 1043 Brussel

nv van publiek recht
BTW BE 0244.142.664
RPR Brussel
http://www.vrt.be/disclaimer