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List:       kde-optimize
Subject:    Yet more "preloading"
From:       Lubos Lunak <l.lunak () suse ! cz>
Date:       2004-03-17 18:09:08
Message-ID: 200403171909.08603.l.lunak () suse ! cz
[Download RAW message or body]

Hello,

 while I was already at it ... see the attached patches. This gives me another 
improvement 18,5s->15s  (that's after the 22,5->18,5 improvement I just 
mentioned in the ld.so madvise post, same machine, same plain KDE session). 
Looks like I was pretty naive to think the system would be actually good at 
quickly loading things from the HDD :(.

 The xdm patch is for SUSE's /etc/init.d/xdm , the paths in it are hardcoded 
for the moment ($KDEDIR is /opt/_k, $KDEHOME /home/kde2/.k, $QTDIR /opt/_q). 
This should be better tested right after reboot, because it seems to be that 
the OOM way of clearing the caches doesn't work that well for inodes.

 The questions, of course, are now:

- can anybody confirm (and give numbers)?

- which directories should be prescanned. In my case the prescanning took 
11,5s , which is noticeably more than the 3s gain. After being more picky 
about $KDEDIR/share and scanning only some of its subdirectories, the time of 
course went down, but so did the gain. I was thinking along the lines that 
there could be a list of directories to scan, most important first, and the 
scanning would go in background until the user actually starts startkde. See 
the next point.
 I actually also tried to do just 'scan /', and but it looks like there's not 
much to gain by scanning more. The rest of the difference compared to the 
completely (logout->login) cached case seem to be actual loading of files, 
which is very likely to be too much to be able to do it.

- where to do this caching. KDM (hello Ossi) and init.d script seem the two 
places where this could be done, it takes some time to log in using kdm, and 
there are definitely placed during init.d startup when the HDD must be pretty 
bored. Ossi, could you please provide some thoughts on this? I don't know how 
that works, and there could be two places where to have this caching running, 
while typing in kdm, and also while initializing X (at least it seem to be 
that while initializing the graphics mode or whatever it's just waiting for 
about two seconds and nothing is really happening).

-- 
Lubos Lunak
KDE developer
---------------------------------------------------------------------
SuSE CR, s.r.o.  e-mail: l.lunak@suse.cz , l.lunak@kde.org
Drahobejlova 27  tel: +420 2 9654 2373
190 00 Praha 9   fax: +420 2 9654 2374
Czech Republic   http://www.suse.cz/

["xdm.patch" (text/x-diff)]

--- xdm.sav	2004-03-17 18:10:54.000000000 +0100
+++ xdm	2004-03-17 18:09:32.000000000 +0100
@@ -63,6 +63,10 @@ DM=${DISPLAYMANAGER##*/}
 rc_reset
 case "$1" in
     start)
+        /tmp/scan /opt/_k/share \
+            /home/kde2/.k /opt/_k/lib \
+            /opt/_q/lib /opt/_q/plugins \
+            -/lib -/usr/lib &
 	echo -n "Starting service $DM"
 	startproc $PIDFILE $DISPLAYMANAGER || rc_failed
 	# After a crash or a kill signal we may have

["scan.cpp" (text/x-c++src)]

#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

void scan( const char* dirname, bool recurse )
    {
    if( chdir( dirname ) < 0 )
        return;
//    if( strcmp( dirname, "/dev" ) == 0 )
//        return;
//    if( strcmp( dirname, "/proc" ) == 0 )
//        return;
//    static int cnt = 0;
//    if( ++cnt % 1000 == 0 )
//        fprintf( stderr, "D:%s\n", dirname );
    if( DIR* dir = opendir( "." ))
        {
        while( dirent* file = readdir( dir ))
            {
            struct stat data;
            if( stat( file->d_name, &data ) < 0 )
                continue;
//            fprintf( stderr, "F:%s\n", file->d_name );
            if( strcmp( file->d_name, "." ) == 0
                || strcmp( file->d_name, ".." ) == 0 )
                continue;
            if( recurse && S_ISDIR( data.st_mode ))
                {
//                fprintf( stderr, "I:%s\n", file->d_name );
                char tmp[ NAME_MAX * 2 + 1 ];
                strcpy( tmp, dirname );
//                if( strcmp( tmp, "/" ) != 0 )
//                    strcat( tmp, "/" );
                strcat( tmp, file->d_name );
                scan( tmp, recurse );
                chdir( dirname );
                }
            }
        closedir( dir );
        }
    }

int main( int argc, char* argv[] )
    {
    for( int i = 1;
         i < argc;
         ++i )
        {
        if( argv[ i ][ 0 ] == '-' )
            scan( argv[ i ] + 1, false );
        else
            scan( argv[ i ], true );
        }
    return 0;
    }


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