Messages in this thread |  | | Date | Wed, 11 Oct 2000 22:23:52 +0100 | From | Stephen Tweedie <> | Subject | Re: Raw i/o usage wrecks block device performance?? |
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Hi,
On Wed, Oct 11, 2000 at 09:28:57PM +0100, Chris Evans wrote: > > The problem is best described with a little sequence. After using raw i/o > facilities, streamed block device reads from the same underlying device > exhibit much poorer performance than before the raw i/o. > > Anyone know what's going on? Looks like a bug or inefficiency somewhere in > the kernel.
It looks as if "hdparm -t" is getting hurt by the fact that raw IO sets the underlying device's blocksize to 512 bytes (Unix APIs require that raw character devices allow arbitrary sector-aligned IO). I'll trace it once I get back from ALS to see if there's anything obviously funny going on.
Cheers, Stephen - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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