I'm all for fixing the slab allocator to allocated from non-cached
memory (heh, trust me - don't look at usb-ohci-sa1111.h :-)
but, shouldn't a distinction be made between hardware cache alignment
and strict hardware required alignment?
hardware cache alignment - nice to have, speeds up the code (a lot)
but things generally/often will work if it's not enforced; (yes, I
know, there are places where it will break code...)
strict hardware required alignment - required by hardware, must have,
driver will not work if it's not enforced.
-brad
David Brownell wrote:
>> Anyways, is this the end of the discussion regarding my patch?
>
>I think one of the maintainers for usb-uhci (Georg) said he'd
>want the general fix ...
>
>> Manfred said plainly "usb-uhci is broken", Alan kinda
>> manuevered around my small problem, Dave Brownell looks
>> unconvinced. So?
>
>There are two problems I see.
>
>(1) CONFIG_SLAB_DEBUG breaks the documented
>requirement that the slab cache return adequately aligned
>data ... which the appended patch should probably handle
>nicely (something like it sure did :-) and with less danger
>than the large patch you posted.
>
>(2) The USB host controller drivers all need something
>like a pci_consistent slab cache, which doesn't currently
>exist. I have something like that in the works, and David
>Miller noted one driver that I may steal from.
>
>- Dave
>
>
>--- slab.c-orig Tue Mar 6 15:01:26 2001
>+++ slab.c Tue Mar 6 15:05:58 2001
>@@ -676,12 +676,10 @@
> }
>
> #if DEBUG
>+ /* redzoning would break cache alignment requirements */
>+ if (flags & SLAB_HWCACHE_ALIGN)
>+ flags &= ~SLAB_RED_ZONE;
> if (flags & SLAB_RED_ZONE) {
>- /*
>- * There is no point trying to honour cache alignment
>- * when redzoning.
>- */
>- flags &= ~SLAB_HWCACHE_ALIGN;
> size += 2*BYTES_PER_WORD; /* words for redzone */
> }
> #endif
>
>
>
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