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

[Chen, Kenneth W]

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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