RE: Direct io on block device has performance regression on 2.6.x kernel

From: Chen, Kenneth W
Date: Wed Mar 09 2005 - 20:55:59 EST

Andrew Morton wrote on Wednesday, March 09, 2005 5:34 PM
> What are these percentages? Total CPU time? The direct-io stuff doesn't
> look too bad. It's surprising that tweaking the direct-io submission code
> makes much difference.

Percentage is relative to total kernel time. There are three DIO functions
showed up in the profile:

__blockdev_direct_IO 4.97%
dio_bio_end_io 2.70%
dio_bio_complete 1.20%

> hm. __blockdev_direct_IO() doesn't actually do much. I assume your damn
> compiler went and inlined direct_io_worker() on us.

We are using gcc version 3.4.3. I suppose I can finger point gcc ? :-P

- Ken

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