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    SubjectRe: 2.6.11-rc1-mm1
    Christoph Hellwig writes:
    > On Fri, Jan 14, 2005 at 04:11:38PM -0500, Karim Yaghmour wrote:
    > > Where does this appear in relayfs and what rights do
    > > user-space apps have over it (rwx).
    > Why would you want anything but read access?

    This would allow an application to write trace events of its own to a
    trace stream for instance. Also, I added a user-requested 'feature'
    whereby write()s on a relayfs channel would be sent to a callback that
    could be used to interpret 'out-of-band' commands sent from the
    userspace application. And if lockless logging were being used, this
    could provide a cheaper way for applications to write to the trace
    buffer than having to do it via syscall.

    > > bufsize, nbufs:
    > > Usually things have to be subdivided in sub-buffers to make
    > > both writing and reading simple. LTT uses this to allow,
    > > among other things, random trace access.
    > I think random access is overkill. Keeping the code simple is more
    > important and user-space can post-process it.
    > > resize_min, resize_max:
    > > Allow for dynamic resizing of buffer.
    > Auto-resizing sounds like a really bad idea.

    It also doesn't seem to be really useful to anyone, so we should
    probably remove it.


    > > init_buf, init_buf_size:
    > > Is there an initial buffer containing some data that should
    > > be used to initialize the channel's content. If you're doing
    > > init-time tracing, for example, you need to have a pre-allocated
    > > static buffer that is copied to relayfs once relayfs is mounted.
    > And why can't you do this from that code? It just needs an initcall-like
    > thing that runs after mounting of relayfs.


    Tom Zanussi <>
    IBM Linux Technology Center/RAS

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