Messages in this thread | | | Subject | Re: CONFIG_BIGMEM and rawio | Date | Fri, 3 Sep 1999 14:06:50 +0100 (BST) | From | Alan Cox <> |
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> On Fri, 3 Sep 1999, Alan Cox wrote: > > >Raw I/O from PCI/ISA space to PCI/ISA space needs bounce buffers on plenty > >of chipsets too > > If the bounce buffer means to pass through an additional piece of > regular-memory, then let the bounce buffer to be the page-cache and don't > use raw-io in first place.
But the user doesn't know which pages are currently bouncable or not. Not using raw I/O has two problems 1. If 99% of your pages could be directly written you lost all the speed 2. You still need the direct I/O uncached properties for some applications like failover across shared disk
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