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Message-ID: <3AA83D12.59B3DB34@cac.co.jp>
Date: Fri, 09 Mar 2001 11:16:50 +0900
From: SUZUKI Koichi <koich@cac.co.jp>
Organization: CAC Corporation
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$BNkLZ$G$9!#(B

$B%9%]%C%H:n6H$7$+$G$-$:$K$9$_$^$;$s!#(B

"file-backed" $B$NLu8l$KG:$_$^$7$?!#(B
$B!V%U%!%$%k$KN"IU$1$5$l$?!W$C$F46$8$G$7$g$&$+(B?
madvise.2 $B$G$O!V%U%!%$%k$K;Y;}$5$l$?!W!"(B
vnconfig.8 (swapfile.8) $B$G$O!V%U%!%$%k$rMQ$$$?!W$H$J$C$F$$$^$9!#(B
$B$3$3$G$O!V%U%!%$%k$rMQ$$$?!W$r;H$o$;$F$$$?$@$-$^$7$?!#(B

$B0J2<$N$h$&$J46$8$G$$$+$,$G$7$g$&!#(B
$B0l1~(B madvise.2 $B$NFbMF$H$b@09g@-$,$H$l$k$H;W$$$^$9!#(B

suzu@front.nest.or.jp wrote:

> .It Dv MAP_NOSYNC
> Causes data dirtied via this VM map to be flushed to physical media
> only when necessary (usually by the pager) rather then gratuitously.

.It Dv MAP_NOSYNC
$B$O$3$N(B VM $B%^%C%W$r7PM3$7$F1x$5$l$?%G!<%?$r!"L50G$K$G$O$J$/(B
($BDL>o$O%Z!<%8%c$K$h$C$F(B) $BI,MW$J;~$N$_J*M}E*$J%a%G%#%"$K(B
$B%U%i%C%7%e$9$k$h$&$K$7$^$9!#(B

 ($B$3$3(B "rather then" $B$G$O$J$/!"(B"rather than" $B$G$O$J$$$G$7$g$&$+(B?)

> Typically this prevents the update daemons from flushing pages dirtied
> through such maps and thus allows efficient sharing of memory across
> unassociated processes using a file-backed shared memory map.

$B0lHLE*$K$3$&$9$k$3$H$G!"$=$N$h$&$J%^%C%W7PM3$G1x$5$l$?%Z!<%8$r(B
$B%"%C%W%G!<%H%G!<%b%s$,%U%i%C%7%e$9$k$3$H$rKI$0$3$H$,$G$-!"(B
$B$3$l$K$h$j4XO"$7$J$$%W%m%;%94V$G!"%U%!%$%k$rMQ$$$?6&M-%a%b%j%^%C%W$r(B
$B;H$C$F$N8zN(E*$J%a%b%j$N6&M-$,$G$-$k$h$&$K$J$j$^$9!#(B

>                                                                Without
> this option any VM pages you dirty may be flushed to disk every so often
> (every 30-60 seconds usually) which can create performance problems if you
> do not need that to occur (such as when you are using shared file-backed
> mmap regions for IPC purposes).

$B$3$N%*%W%7%g%s$,$J$$$H!"1x$5$l$?(B VM $B%Z!<%8$OIQHK(B ($BDL>o(B 30-60 $BICKh(B) $B$K(B
$B%G%#%9%/$K%U%i%C%7%e$5$l$k$+$bCN$l$:!"$=$N$h$&$JF0:n$rI,MW$H$7$J$$>l9g(B
($BNc$($P(B IPC $B$N$?$a$K%U%!%$%k$rMQ$$$?6&M-(B mmap $BNN0h$rMQ$$$F$$$k>l9g(B)
$B%Q%U%)!<%^%s%9$KLdBj$,=P$k$3$H$,$"$j$^$9!#(B

>                                  Note that VM/filesystem coherency is
> maintained whether you use MAP_NOSYNC or not.

MAP_NOSYNC $B$r;H$C$F$$$k$+$K$+$+$o$i$:!"(B
VM/ $B%U%!%$%k%7%9%F%`$N0l4S@-$OJ]$?$l$k$3$H$KCm0U$7$F$/$@$5$$!#(B

>                                                This option is not portable
> across UNIX platforms (yet), though some may implement the same behavior
> by default.

$B$3$N%*%W%7%g%s$O(B UNIX $B%W%i%C%H%U%)!<%`4V$G(B ($B$^$@(B) $B0\?"@-$O$"$j$^$;$s$,!"(B
$B$$$/$D$+$N%W%i%C%H%U%)!<%`$G$O%G%U%)%k%H$GF1$8?6$kIq$$$r$9$k$h$&$K(B
$B<BAu$5$l$F$$$k$+$bCN$l$^$;$s!#(B

--
This is my STYLE.
$B$9$:$-$3!<$$$A(B
