Messages in this thread | | | Subject | Re: [PATCH] msr v3 available | Date | Thu, 28 Jan 1999 09:52:53 -0800 | From | Craig Milo Rogers <> |
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>> - Included patch which adds an ioctl() on /proc/<pid>/mem for >> translating virtual to physical addresses > >Users have no business knowing what physical addresses >are being used.
Actually, there are several instances in which this information is of benefit to users, even non-admin users. Off the top of my head:
1) Users who experiance variable performance in a compute-intensive task might want to investigate which physical memory pages their application is using. There could be a cache thrashing problem, as Richard demonstrated, or there could be uncached regions of memory, as occurs on some x86 configurations.
2) Users who experience *incorrect* calculations might look for a correlation with physical memory. This can happen; I have seen it. Sometimes, with marginal memory chips, the timing is so critical that only certain programs fails, and only with certain data (gcc is the prime example). It is helpful to know all the potential factors when debugging.
3) I/O problems can also be sensitive to physical memory address.
Finally, if Richard's patch, or something like it, could be used to feed a program that displayed a map of physical memory and showed which pages were mapped to which processes, well, that would be just too cool!
Craig Milo Rogers
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