Messages in this thread | | | Date | Wed, 9 Apr 2008 14:15:46 -0700 | From | Greg KH <> | Subject | Re: [PATCH 0/3] x86: add cpus_scnprintf function v3 |
| |
On Wed, Apr 09, 2008 at 01:59:39PM -0700, Mike Travis wrote: > 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?
Documentation/filesystems/sysfs.txt, while a bit outdated, still contains this rule.
> 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
That's fine, it's /proc/, not /sys/ :)
thanks,
greg k-h
| |