Messages in this thread | | | Date | Wed, 8 Aug 2012 20:09:44 -0700 (PDT) | From | Hugh Dickins <> | Subject | RE: [PATCH 1/1] proc: add /proc/pid/shmaps |
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On Thu, 9 Aug 2012, Ren, Qiaowei wrote: > On Wed, 8 Aug 2012, David Rientjes wrote: > > On Wed, 8 Aug 2012, Qiaowei Ren wrote: > > > > > Add a shmaps entry to /proc/pid: show information about shared memory in an address space. > > > > > > People that use shared memory and want to perform an analyzing about it. For example, judge whether any memory address is shared. This file just contains 'share' part of /proc/pid/maps now. There are too many contents in maps, and so we have to do a lot of analysis to obtain relative information every time. > > > > > > Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com> > > > > Nack as unnecessary; /proc/pid/maps already explicitly emits 's' for VM_MAYSHARE and 'p' otherwise so this information is already available to userspace. > > > > Thanks for your reply. There are so many contents in /proc/pid/maps, and usually only a very small minority of those are about shared memory in address space of every process. So I hope that a new file maybe provide some convenience. Could you tell me how to get such information except analyzing 'maps' file?
You are joking? Please imagine what the kernel and /proc would look like if it provided a personally tailored /proc file to everybody who could not be bothered to parse the information already shown there.
Sure, there is already lots of ugly and duplicative junk under /proc, which usually has to be kept to preserve back compatibility; but please do not try to add to it.
There is sometimes an excuse if some fields of an existing /proc file are significantly more expensive for the kernel to compute than others: then a file which separates them can save processing. But that is definitely not the case here.
A side issue would be whether parsing /proc/pid/maps for 's' VM_MAYSHARE mappings (or your equivalent patch) actually tells you what you want to know about "shared memory" - that would depend on what you really want to know, and what you mean by shared memory.
Hugh
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