Re: [PATCH rdma-next 0/8] Introduce mlx5 Memory Scheme ODP

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2024/9/8 14:18, Michael Guralnik 写道:
> 
> On 06/09/2024 08:35, Zhu Yanjun wrote:
>>
>> As such, it seems that it can save memory via not pinning down the
>> underlying physical pages of the address space, and track the validity
>> of the mappings.
>>
>> What is the difference on the performance with/without ODP enabled? And
>> about memory usage, is there any test result about this?
>>
>> And ODP can be used mlx5 IB device? Or ODP can only be used in mlx5
>> RoCEv2 device?
>>
> The performance while using ODP is highly dependent on many factors that 
> dictate how many page faults the kernel will have to deal with.
> Each page fault will introduce a latency hit.
> 
> Both the examples in rdma_core (e.g ibv_rc_pingpong) and the perftest 
> (e.g. ib_write_bw) support running with ODP to test this.

Thanks a lot. I have developed ODP for other RDMA devices. From my 
tests, it seems that with ODP, the system memory is needed less than 
without ODP.

 From your descriptions, it seems that the latency of RDMA will increase 
if I get you correctly.

If others (for example, bandwidth) remain unchanged, the tradeoff should 
be between memory and latency.

Best Regards,
Zhu Yanjun

> 
> ODP can be used in both IB and RoCE.
> 
> 
> Michael
> 
> 
>> Thanks,
>> Zhu Yanjun
>>