Messages in this thread | | | Subject | Re: [PATCH 1/2] Report the pagesize backing a VMA in /proc/pid/smaps | From | Dave Hansen <> | Date | Wed, 24 Sep 2008 12:23:10 -0700 |
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On Wed, 2008-09-24 at 20:11 +0100, Mel Gorman wrote: > I don't get what you mean by it being sprinkled in each smaps file. How > would you present the data?
1. figure out what the file path is from smaps 2. look up the mount 3. look up the page sizes from the mount's information
> > We should be able to figure out which > > mount the file is from and, from there, maybe we need some per-mount > > information exported. > > Per-mount information is already exported and you can infer the data about > huge pagesizes. For example, if you know the default huge pagesize (from > /proc/meminfo), and the file is on hugetlbfs (read maps, then /proc/mounts) > and there is no pagesize= mount option (mounts again), you could guess what the > hugepage that is backing a VMA is. Shared memory segments are a little harder > but again, you can infer the information if you look around for long enough. > > However, this is awkward and not very user-friendly. With the patches (minus > MMUPageSize as I think we've agreed to postpone that), it's easy to see what > pagesize is being used at a glance. Without it, you need to know a fair bit > about hugepages are implemented in Linux to infer the information correctly.
I agree completely. But, if we consider this a user ABI thing, then we're stuck with it for a long time, and we better make it flexible enough to at least contain the gunk we're planning on adding in a small number of years, like the fallback. We don't want to be adding this stuff if it isn't going to be stable.
-- Dave
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