Messages in this thread | | | From | (Alan Cox) | Subject | Re: Porting Greg Lehey's rawio.c from FreeBSD to Linux... | Date | Tue, 4 May 1999 17:52:33 +0100 (BST) |
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> Now, I understand that normally, Linux does not allow access to raw > disk devices, but this is a case where I want to test the hardware
The notion of 'raw' disk is foreign to Linux. Its a Unixism. The block device interface is used instead. That isnt optimised for performance however (ie heavy readahead etc)
> configuration and the stripe size I've used for our drive array, and I > want to eliminate any variables that depend on other things like buffer > cache, etc....
If you want to get an accurate disk/controller benchmark you might want to get Stephen Tweedie's O_DIRECT patches (ftp.linux.org.uk/pub/sct) which give you what are logically the same thing - uncached I/O from the disk itself. My only concern is that if FreeBSD does do a copy through kernel space for its raw devices you may not be making an appropriate comparison benchmark for some things as Linux would be going userspace->media
Alan
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