Frithiof Jensen 4f423ddf56 [PATCH] EDAC: Add memory scrubbing controls API to core ... This is an attempt of providing an interface for memory scrubbing control in EDAC. This patch modifies the EDAC Core to provide the Interface for memory controller modules to implment. The following things are still outstanding: - K8 is the first implemenation, The patch provide a method of configuring the K8 hardware memory scrubber via the 'mcX' sysfs directory. There should be some fallback to a generic scrubber implemented in software if the hardware does not support scrubbing. Or .. the scrubbing sysfs entry should not be visible at all. - Only works with SDRAM, not cache, The K8 can scrub cache and l2cache also - but I think this is not so useful as the cache is busy all the time (one hopes). One would also expect that cache scrubbing requires hardware support. - Error Handling, I would like that errors are returned to the user in "terms of file system". - Presentation, I chose Bandwidth in Bytes/Second as a representation of the scrubbing rate for the following reasons: I like that the sysfs entries are sort-of textual, related to something that makes sense instead of magical values that must be looked up. "My People" wants "% main memory scrubbed per hour" others prefer "% memory bandwidth used" as representation, "bandwith used" makes it easy to calculate both versions in one-liner scripts. If one later wants to scrub cache, the scaling becomes wierd for K8 changing from "blocks of 64 byte memory" to "blocks of 64 cache lines" to "blocks of 64 bit". Using "bandwidth used" makes sense in all three cases, (I.M.O. anyway ;-). - Discovery, There is no way to discover the possible settings and what they do without reading the code and the documentation. *I* do not know how to make that work in a practical way. - Bugs(??), other tools can set invalid values in the memory scrub control register, those will read back as '-1', requiring the user to reset the scrub rate. This is how *I* think it should be. - Afflicting other areas of code, I made changes to edac_mc.c and edac_mc.h which will show up globally - this is not nice, it would be better that the memory scrubbing fuctionality and interface could be entirely contained within the memory controller it applies to. Frithiof Jensen edac_mc.c and its .h file is a CORE helper module for EDAC driver modules. This provides the abstraction for device specific drivers. It is fine to modify this CORE to provide help for new features of the the drivers doug thompson Signed-off-by: Frithiof Jensen <frithiof.jensen@ericson.com> Signed-off-by: doug thompson <norsk5@xmission.com> Acked-by: Alan Cox <alan@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2007-02-12 09:48:32 -08:00
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edac.txt	[PATCH] EDAC: Add memory scrubbing controls API to core	2007-02-12 09:48:32 -08:00