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
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