Messages in this thread | | | Date | Wed, 1 Sep 2004 08:32:19 +0100 | From | viro@parcelfa ... | Subject | Re: f_ops flag to speed up compatible ioctls in linux kernel |
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On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote: > Hello! > Currently, on the x86_64 architecture, its quite tricky to make > a char device ioctl work for an x86 executables. > In particular, > 1. there is a requirement that ioctl number is unique - > which is hard to guarantee especially for out of kernel modules
Too bad.
> 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.
Excuse me, but I have zero sympathy to people who complain about obstacles to dumping more into the same piles - it should be hard. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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