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Re: MAXACTION exceeded error while using systemtap
> > I think that SystemTap needs some method to periodically (or when memory
> > pressure arrives) dump the parts of the array to userspace via
> > relayfs.
>
> See my previous reply for one way you could do this i.e. the
> kmalloc-stacks example.
Will take a look - seems promising.
> > relayfs already supports such mechanism with its "sub-buffer" structure,
> > where the userspace reader is allowed to read full buffers (thus freeing
> > them afterwards) while the hooks continue to push data to empty or
> > partially filled buffers.
> >
> > James mentions that
> >
> > "btw MAXACTION really can't work reliably what happens when the box is
> > underload, say with 4 gigabit nics all being flooded with data, and
> > you are probing a function in the fast path?
> >
> > Not everyone has a box that can sum 4 billion numbers in less than a minute."
> >
> > relayfs works in two modes once its memory pool is full:
> >
> > - panic's
> > - drops new entries
> >
> > I imagine that by using relayfs to send data to userspace one should
> > automatically get those very important features.
>
> I'm not sure what you mean - relayfs can be used in either 'overwrite'
> or 'no-overwrite' modes; if its memory pool is full, 'overwrite' mode
> overwrites the oldest entries, while 'no-overwrite' mode drops new
> entries - there should be no 'panic's' anywhere in there. ;-)
Indeed - there's no "panic" anywhere. Your description is accurate (unlike
mine's) :)