Messages in this thread | | | Date | Wed, 09 Apr 2008 13:59:39 -0700 | From | Mike Travis <> | Subject | Re: [PATCH 0/3] x86: add cpus_scnprintf function v3 |
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Greg KH wrote: > On Wed, Apr 09, 2008 at 07:51:23PM +0200, Bert Wesarg wrote: >> On Tue, Apr 8, 2008 at 8:43 PM, Mike Travis <travis@sgi.com> wrote: >>> * Cleanup usages of cpumask_scprintf in the following files and add >>> another interface to use cpulist_scnprintf where appropriate. >> On Mon, Apr 7, 2008 at 8:22 PM, Mike Travis <travis@sgi.com> wrote: >>> Part of the change is readability, but also looking towards the future >>> of 16k/64k/??? # of cpus, the straight mask approach will overflow the >>> PAGE_SIZE buffer provided (though some pathological cases will overflow >>> the range method as well.) So we'll need some advancement in the format >>> of the printout. >> Btw, I think you can now push for a deprecation of the 'old' mask >> attributes, with the justification you have given above. The other >> possibility is to change sysfs to provide bigger attribute buffers >> (CCed Greg for this). > > Huh? > > sysfs is "one value per file", if you are getting close to PAGE_SIZE in > any sysfs file, then you are doing something very wrong. > > What sysfs file currently is trying to output data this big? > > thanks, > > greg k-h
Hi Greg,
There's none at the moment. The increase is coming from printing the cpuset for various attributes, like cpus on a node, etc. Since it uses cpumask_scnprintf(), this prints a bit map representing a cpumask_t.
With the increase to 4096 cpus, this string is now 1152 bytes long. The next iteration will have 16384 cpus which will need 4608 bytes to fully display, overflowing a standard page. I've added alternate interfaces that use cpulist_scnprintf() which has the advantage of collapsing the bits into ranges. This though can result in a much larger output size if, for example only every other bit is set.
Btw, where does one value per file come from? I see outputs like:
# cat /proc/self/stat 4313 (cat) R 4218 4313 4218 34816 4313 4194304 207 0 0 0 0 0 0 0 20 0 1 0 6802916 5672960 131 18446744073709551615 4194304 4212948 140735962676160 18446744073709551615 140499600349840 0 0 0 0 0 0 0 17 3 0 0 0 0 0
Thanks, Mike
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