On 06/05/2012 03:03 PM, Cedric Blancher wrote:
On 5 June 2012 09:11, Michal Hlavinka<[email protected]> wrote:
On 06/01/2012 02:32 PM, Irek Szczesniak wrote:
Michal, did anyone ever filed a bug against Linux's FIFO/PIPE
implementations to support I_PEEK? As far as I can check all SystemV
derivatives (including Solaris), AIX and HP/UX support I_PEEK on pipes
and fifos.
I don't know if there was any official attempt. I asked a few kernel
developers in person and they told me that no one will bother with this.
<rant>
Michal, I recall that Redhat staff once ridiculed and mocked a patch
(...why add extra performance support for a dead OS [Solaris] ...)
which added support for I_PEEK to bash2 and finally convinced the
maintainers NOT to take it. So basically this issue is blocked from
both sides, kernel and bash, by Redhat.
Why?
</rant>
I'm not aware about anything related, so I can't answer your
ran^W^W^Wquestion.
As for an implementation in the Linux fifo kernel module, the I_PEEK
ioctl() can be implemented along the lines of a read() syscall but
without disposing the data which have been read. An implementation
should therefore be very easy and should give the shells in Linux a
SERIOUS performance advantage. I'm wondering why Redhat isn't
interested in performance. Oh yes, see<rant />
Cedric was somewhat right in his reply. There are a lot of processes
which are quite resource demanding even for one line change. Also, there
is always more work than what can be done (especially on kernel side.
afaik, we're still hiring ;-) ). If someone does X, it means he won't be
able to do Y. So, we do what product management tell us to do.
Also, please don't forget that Red Hat is only Linux, but Linux is not
only Red Hat. (Well, nowadays even the first part is no longer
completely true.) I wanted to add I_PEEK feature request to upstream
bugzilla, but I've been told that it does not work that way. It'd rot
there for ages until someone would close that a few years later during
some bugzilla clean up.
Anyway, I found up a few colleagues willing to code it. I need a
feature request to be filed now. I'm going to ask a few customers who
complained about 'connection reset by peer' messages if they are willing
to do it. If I fail, I'll try to convince them to code it in their spare
time.
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