On Fri, 26 Oct 2012 16:57:27 +0200 Roland Mainz wrote:
> On Wed, Oct 24, 2012 at 7:07 PM, Glenn Fowler <g...@research.att.com> wrote:
> > On Sat, 20 Oct 2012 19:53:46 +0200 Cedric Blancher wrote:
> >> On 19 October 2012 03:29, ÏÌØÇÁ ËÒÙÖÁÎÏ×ÓËÁÑ
> >> <olga.kryzhanov...@gmail.com> wrote:
> >> > Glenn, David, Suse 12.2, with ast-ksh.20121016 command substitutions
> >> > still use read() to read data instead of mmap(), as you can see with
> >> > this tests:
> >> > strace ~/bin/ksh -c 'x=$(seq 400000) ; true' 2>&1 | fgrep 'read(' | wc -l
> >> > 50
> >> > strace ~/bin/ksh -c 'x=$(seq 800000) ; true' 2>&1 | fgrep 'read(' | wc -l
> >> > 92
> >> > strace ~/bin/ksh -c 'x=$(seq 1600000) ; true' 2>&1 | fgrep 'read(' | wc
> >> > -l
> >> > 187
> >> >
> >> > The builtin cat command does not use mmap() either, as you can see in
> >> > this tests:
> >> > strace ~/bin/ksh -c 'builtin cat ; builtin rm ; seq 1600000 >s1 ; cat
> >> > s1 >s2 ; rm s1 s2' 2>&1 | fgrep 'read(' | wc -l
> >> > 187
> >> > strace ~/bin/ksh -c 'builtin cat ; builtin rm ; seq 3200000 >s1 ; cat
> >> > s1 >s2 ; rm s1 s2' 2>&1 | fgrep 'read(' | wc -l
> >> > 382
> >> > strace ~/bin/ksh -c 'builtin cat ; builtin rm ; seq 6400000 >s1 ; cat
> >> > s1 >s2 ; rm s1 s2' 2>&1 | fgrep 'read(' | wc -l
> >> > 773
> >> >
> >> > On Solaris, the Sun /usr/bin/cat uses mmap(), and for this reason, out
> >> > runs AST cat, even the libcmd built in version, by a factor of 1.9-2.7
> >> > for files larger than 10MB.
> >
> >> David, Glenn, can you try to fix this for the next alpha, please? It
> >> seems this has a larger performance impact for large datasets on busy
> >> systems (i.e. "big data) and send the patch for ast-ksh 2012-10-16 to
> >> me (and anyone else interested, too)
> >
> > the next alpha will have this working in builtins for sfio input streams
> > other than sfstdin -- a bit more design is needed to handle sfstdin
> Erm... just curious: sfstdin from pipe can't be |mmap()|'ed in any
> sane or mad way... but what is the problem if sfstdin points to a
> normal, plain file ?
the problem is not insurmountable
its just that in pre-libcmd-builtin days ksh regined supreme over
sfstdin,sfstdout,sfstderr
and at times this clashes with builtins wanting to do the same
streams sfopen()'d by builtins are not a problem
dgk knows what needs to be done
but we've already changed enough for the next alpha
(and are still debugging some of those changes before posting)
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