From: Tom Zanussi <zanussi@us.ibm.com>
To: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>,
James Dickens <jamesd.wi@gmail.com>,
systemtap@sources.redhat.com
Subject: Re: MAXACTION exceeded error while using systemtap
Date: Wed, 28 Dec 2005 20:12:00 -0000 [thread overview]
Message-ID: <17330.60599.330907.78327@tut.ibm.com> (raw)
In-Reply-To: <20051228164538.GA3709@dmt.cnet>
Marcelo Tosatti writes:
> On Thu, Dec 08, 2005 at 08:57:46AM -0500, Frank Ch. Eigler wrote:
> > Hi -
> >
> > jamesd.wi wrote:
> >
> > > [...] perhaps you two, should look at how your neighbor DTrace
> > > deals with this issue. It seems to work pretty well.
> >
> > Their situation is a little simpler because the language forbids
> > looping and recursion, so the individual handler run times are already
> > statically bounded.
> >
> >
> > > [...] 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?
> >
> > Yes, this is a good point. A system-level watchdog would be useful.
> >
> >
> > > P.S. I would recomend the members of this list subscribe to the
> > > dtrace-discuss list on www.opensolaris.org, its a low traffic list,
> > > but they do discuss issues you will face as you proceed. I can
> > > assure that the dtrace programers monitor your mailing list.
> >
> > Good point. Welcome all, and feel free to delurk.
>
> Hi folks,
>
> 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.
>
> 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. ;-)
Tom
next prev parent reply other threads:[~2005-12-28 19:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-06 21:56 Stone, Joshua I
2005-12-06 22:11 ` Frank Ch. Eigler
2005-12-07 20:53 ` Martin Hunt
2005-12-07 21:09 ` Frank Ch. Eigler
2005-12-07 22:29 ` Martin Hunt
2005-12-07 23:07 ` Frank Ch. Eigler
2005-12-08 8:55 ` Martin Hunt
2005-12-08 12:52 ` James Dickens
2005-12-08 13:57 ` Frank Ch. Eigler
2005-12-28 19:06 ` Marcelo Tosatti
2005-12-28 20:12 ` Tom Zanussi [this message]
2005-12-28 20:38 ` Marcelo Tosatti
2005-12-28 21:13 ` Frank Ch. Eigler
2005-12-08 13:37 ` Frank Ch. Eigler
-- strict thread matches above, loose matches on Subject: below --
2005-12-08 17:50 Stone, Joshua I
2005-12-06 20:41 Stone, Joshua I
2005-12-06 20:55 ` Frank Ch. Eigler
2005-12-06 16:40 Badari Pulavarty
2005-12-06 16:59 ` Frank Ch. Eigler
2005-12-07 1:10 ` Badari Pulavarty
2005-12-07 15:21 ` William Cohen
2005-12-07 16:37 ` Badari Pulavarty
2005-12-06 17:01 ` Hien Nguyen
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