Can someone please elaborate on the acronym KVA ?

$ sysctl -d kern.ipc.maxpipekva
kern.ipc.maxpipekva: Pipe KVA limit

This doesn't tell me enough.

 - aW



        On Tue, Nov 11, 2003 at 04:46:47AM +1100, Bruce Evans wrote:

        > > I came in to work today to find one of my -current machines unable to
        > > open a pipe.  (This probably had a lot to do with the spamd that went
        > > stark raving nutters overnight, but that's a separate problem.)  A
        > > power cycle fixed the problem, but /var/log/messages was filled with:
        > >
        > > Nov 10 11:05:44 bewilderbeast kernel: kern.maxpipekva exceeded, please see 
tuning(7).
        > >
        > > Interesting.
        > >
        > > bewilderbeast~;sysctl kern.maxpipekva
        > > sysctl: unknown oid 'kern.maxpipekva'
        > > bewilderbeast~;
        > 
        > The following patch fixes this and some nearby style bugs:
        > - source style bug: line too line
        > - output style bugs: comma splice, verboseness (helps make the source line
        >   too long), and kernel message terminated with a ".".
        > 
        > %%%
        > Index: sys_pipe.c
        > ===================================================================
        > RCS file: /home/ncvs/src/sys/kern/sys_pipe.c,v
        > retrieving revision 1.158
        > diff -u -2 -r1.158 sys_pipe.c
        > --- sys_pipe.c        9 Nov 2003 09:17:24 -0000       1.158
        > +++ sys_pipe.c        10 Nov 2003 17:21:47 -0000
        > @@ -331,5 +331,5 @@
        >       if (error != KERN_SUCCESS) {
        >               if (ppsratecheck(&lastfail, &curfail, 1))
        > -                     printf("kern.maxpipekva exceeded, please see 
tuning(7).\n");
        > +                     printf("kern.ipc.maxpipekva exceeded; see 
tuning(7)\n");
        >               return (ENOMEM);
        >       }
        > %%%
        > 
        > > And tuning(7) doesn't mention this, either.
        > >
        > > Is this just work-in-progress, or did someone forget to commit something?
        > 
        > Seems like tuning pipe kva is completely absent in tuning(7) (so the above
        > message can be shortened further).  You can tune kva generally as documented
        > there, but the pipe limit is separate.
        > 
        > > PS: Lesson of the day: no pipe KVA, no su.  Great fun on remote
        > > machines!  :-)
        > 
        > It's interesting that su was the point of failure.  It uses a pipe hack
        > for IPC.  Otherwise it doesn't use pipes, at least direectly.  It
        > shouldn't need to use the pipe hack.  My version uses signals instead.
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