Hello Community,
I am running QNX 6.5 on a normal consumer PC. Unfortunately, the performance of the HD is not so good, so I had a look at the arguments used to start the ahci driver. It looks like this.
“devb-ahci blk vnode=20000,cache=150m,noatime,delwri=0,commit=medium,automount=hd0t79:/:qnx4:unbusy”
Is there a way to change the arguments of the driver on a test basis? What settings would you recommend and what would be the workflow for customizing the arguments.
Many thanks
What do you mean when you say performance is ‘not so good’?
Are you using an SSD or a hard drive?
How much performance do you need?
Tim
If you are comparing the performance to a Linux or Windows system, the difference is well known. It’s one of the few issues with QNX that is inferior to other monolitic kernel OS’s. It is doubtful that changing the disk parameters will help much, but if you want to, there is a convenient way,
The OS works fine without a hard drive. You can slay the driver and restart the driver. You should be able to find the driver under /proc in the filesystem that is part of the boot image. Once you restart the driver you will need to mount its partitions and then mount one of its partitions as root.
Thank you for explanation
So a couple of things here based on your PM (so everyone can see the answer)
How much output are you getting from the -V option? It is constantly updating the screen? If it is doing that it’s possible that the updates to the screen are slowing down the copy process especially if your video driver etc isn’t particularly fast.
The other thing I’m assuming is that bigfile and the /tmp directory are on the same harddrive? If so your speed is going to be slower than you might expect because you have to ‘read’ from the bigfile file on hard drive in some track/sector and then write to a different track/sector for /tmp. In general I’d expect your performance to be halfed since both files are on the same hard drive.
To fix the first problem I suggest you use the ‘time’ command built into the QNX shell:
time cp bigfile /tmp
and see how many seconds that takes. Then divide filesize/seconds to get your rate per second.
To truly see the Read or Write performance of the drive (and devb-ahci) you should create a RAM disk and put your ‘bigfile’ in the RAM disk. Then copy from the RAM disk to the hard drive and see how long that takes. Then do the reverse (copy bigfile from the hard drive to the RAM drive) and see how long that takes.
I can’t recall whether you enabled caching or not on devb-achi. You might adjust that once you try doing what I suggested above.
Tim