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Date:      Tue, 16 Feb 1999 02:11:18 +1100
From:      Bruce Evans <bde@zeta.org.au>
To:        bde@zeta.org.au, dillon@apollo.backplane.com
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: Weird piecemeal reads over socketpair() pipe breaks up small writes into even smaller reads.
Message-ID:  <199902151511.CAA00760@godzilla.zeta.org.au>

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>    Ok, so perhaps tweeking the rescheduling changes in kern_subr.c to
>    not try to do it in the first few thousand bytes copied is the solution?

kern_subr.c can't do that, because `struct uio' doesn't give the original
count.

>    Would you like to do it or should I?  This isn't high priority but it
>    should definitely not be rescheduling after the first 96 bytes.  That's
>    just a waste of cpu.

The waste for rescheduling should be insignificant, since it should only
occur every ROUNDROBIN_INTERVAL (default 100 msec).  It actually seems
to be rescheduling more often.  Rescheduling _after_ the first 96 bytes
is surprising, since the rescheduling is done before doing any i/o, so
sync effects from sleep(1) should cause rescheduling before any i/o is
done.  Then the reader won't run, but other processes may.

Bruce

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