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

[Chen, Kenneth W]

Andrew Morton wrote on Thursday, March 10, 2005 12:31 PM
> >  > Fine-grained alignment is probably too hard, and it should fall back to
> >  > __blockdev_direct_IO().
> >  >
> >  > Does it do the right thing with a request which is non-page-aligned, but
> >  > 512-byte aligned?
> >  >
> >  > readv and writev?
> >  >
> >
> >  That's why direct_io_worker() is slower.  It does everything and handles
> >  every possible usage scenarios out there.  I hope making the function fatter
> >  is not in the plan.
>
> We just cannot make a change like this if it does not support readv and
> writev well, and if it does not support down-to-512-byte size and
> alignment.  It will break applications.

I must misread your mail.  Yes it does support 512-byte size and alignment.
Let me work on the readv/writev support (unless someone beat me to it).

- Ken


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