Re: performance regression noted in v5.11-rc after c062db039f40

[Lu Baolu <baolu.lu@linux.intel.com>]

On 1/19/21 10:37 PM, Chuck Lever wrote:
> 
> 
>> On Jan 18, 2021, at 8:22 PM, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>>
>> Do you mind posting the cap and ecap of the iommu used by your device?
>>
>> You can get it via sysfs, for example:
>>
>> /sys/bus/pci/devices/0000:00:14.0/iommu/intel-iommu# ls
>> address  cap  domains_supported  domains_used  ecap  version
> 
> [root@manet intel-iommu]# lspci | grep Mellanox
> 03:00.0 Network controller: Mellanox Technologies MT27520 Family [ConnectX-3 Pro]
> [root@manet intel-iommu]# pwd
> /sys/devices/pci0000:00/0000:00:03.0/0000:03:00.0/iommu/intel-iommu
> [root@manet intel-iommu]# for i in *; do   echo -n $i ": ";   cat $i; done
> address : c7ffc000
> cap : d2078c106f0466

MGAW: 101111 (supporting 48-bit address width)
SAGAW: 00100 (supporting 48-bit 4-level page table)

So the calculation of domain->domain.geometry.aperture_end is right.

> domains_supported : 65536
> domains_used : 62
> ecap : f020de
> version : 1:0
> [root@manet intel-iommu]#
> 
> 
>>> Fwiw, this system uses the Intel C612 chipset with Intel(R) Xeon(R)
>>> E5-2603 v3 @ 1.60GHz CPUs.
>>
>> Can you please also hack a line of code to check the return value of
>> iommu_dma_map_sg()?
> 
> diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
> index baca49fe83af..e811562ead0e 100644
> --- a/net/sunrpc/xprtrdma/frwr_ops.c
> +++ b/net/sunrpc/xprtrdma/frwr_ops.c
> @@ -328,6 +328,7 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
>   
>          dma_nents = ib_dma_map_sg(ep->re_id->device, mr->mr_sg, mr->mr_nents,
>                                    mr->mr_dir);
> +       trace_printk("ib_dma_map_sg(%d) returns %d\n", mr->mr_nents, dma_nents);
>          if (!dma_nents)
>                  goto out_dmamap_err;
>          mr->mr_device = ep->re_id->device;
> 
> During the 256KB iozone test I used before, this trace log is generated:
> 
>     kworker/u28:3-1269  [000]   336.054743: bprint:               frwr_map: ib_dma_map_sg(30) returns 1
>     kworker/u28:3-1269  [000]   336.054835: bprint:               frwr_map: ib_dma_map_sg(30) returns 1
>     kworker/u28:3-1269  [000]   336.055022: bprint:               frwr_map: ib_dma_map_sg(4) returns 1
>     kworker/u28:3-1269  [000]   336.055118: bprint:               frwr_map: ib_dma_map_sg(30) returns 1
>     kworker/u28:3-1269  [000]   336.055312: bprint:               frwr_map: ib_dma_map_sg(30) returns 1
>     kworker/u28:3-1269  [000]   336.055407: bprint:               frwr_map: ib_dma_map_sg(4) returns 1

This is the result after commit c062db039f40, right? It also looks good
to me. Are you using iotlb strict mode (intel_iommu=strict) or lazy mode
(by default)?

Best regards,
baolu
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