# PCI driver load is degrading the performance of other device



## vadiraj (Dec 23, 2013)

Hi,

I've ported a NVRAM PCI card driver from Linux to freebsd FreeBSD. The issue I'm facing is, once the driver module is loaded all other related device start performing very bad along with this device.

Details below.

 It*'*s a NVRAM card, hence the storage device is created through the PCI driver module. 
 The driver uses DMA mapping and reserves not more than 512K memory for DMA mapping. 
 The device works fine and I'm able to interact with the firmware and perform the use cases of the device.

The performance is very slow which I believed to be a problem with the driver but, the concern here is, after I load the module, the devices which were performing as expected start performing very slow. I used a RAM disk (md0 created using mdmfs) which drops its performance once I load my driver module. Even tried the use case with SSD disks. The same behavior, the drive performance drops 10 times once my driver is loaded. I understand that the common layer between these devices is GEOM. 

I'm new to the freebsd FreeBSD kernel hence I'm stuck at pointers to look at. Any pointers to start would be of great help to me.

Thanks in advance,


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## trh411 (Dec 23, 2013)

*Re: PCI driver load is degrading the performance of other de*

You may be better advised to post to the `[file]freebsd-drivers@freebsd.org[/file]` mailing list, which deals with writing device drivers for FreeBSD and is subscribed to by like minded folks.


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