Re: f_ops flag to speed up compatible ioctls in linux kernel

[Michael S. Tsirkin]

Hello!
Please do not mail me directly.

Quoting viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) "Re: f_ops flag to speed up compatible ioctls in linux kernel":
> On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote:
> >    2. there's a performance huge overhead for each compat call - there's
> >       a hash lookup in a global hash inside a lock_kernel -
> >       and I think compat performance *is* important.
> > 
> > Further, adding a command to the ioctl suddenly requires changing
> > two places - registration code and ioctl itself.
> 
> So don't add them.  Adding a new ioctl is *NOT* a step to be taken lightly -
> we used to be far too accepting in that area and as somebody who'd waded
> through the resulting dungpiles over the last months I can tell you that
> result is utterly revolting.

Why make it a bigger dungpile then?
And what about the performance overhead?

MST
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