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Fix performance bug on hosts with large

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/var/adm/wtmp files with no boot records.

(boot_time_initialized): New var.
(init_filelock): Initialize it.
(get_boot_time): Use it, instead of nonzero boot_time,
to test whether boot_time is initialized.
Don't invoke utmp routines when dumping.

(get_boot_time): First, try to get the boot time from the
current utmp file, as this can be much faster.  Don't try to
get the boot time from utmp and/or wtmp more than once.

(get_boot_time_1): When passed null pointer, don't invoke utmpname.
New arg LATEST.  All uses changed.
This commit is contained in:
Richard M. Stallman 1999-05-19 01:30:15 +00:00
parent fc303b0a67
commit b97771fc17
1 changed files with 52 additions and 16 deletions
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50
src/filelock.c
View file

@ -1,4 +1,5 @@
/* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
/* Lock files for editing.
Copyright (C) 1985, 86, 87, 93, 94, 96, 98, 1999 Free Software Foundation, Inc.
This file is part of GNU Emacs.
@ -104,6 +105,7 @@ extern int errno;
/* Return the time of the last system boot. */
static time_t boot_time;
static int boot_time_initialized;
extern Lisp_Object Vshell_file_name;
@ -115,8 +117,9 @@ get_boot_time ()
EMACS_TIME time_before, after;
int counter;
if (boot_time)
if (boot_time_initialized)
return boot_time;
boot_time_initialized = 1;
EMACS_GET_TIME (time_before);
@ -166,11 +169,27 @@ get_boot_time ()
#endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */
#if defined (BOOT_TIME) && ! defined (NO_WTMP_FILE)
#ifndef CANNOT_DUMP
/* The utmp routines maintain static state.
Don't touch that state unless we are initialized,
since it might not survive dumping. */
if (! initialized)
return boot_time;
#endif /* not CANNOT_DUMP */
/* Try to get boot time from utmp before wtmp,
since utmp is typically much smaller than wtmp.
Passing a null pointer causes get_boot_time_1
to inspect the default file, namely utmp. */
get_boot_time_1 ((char *) 0, 0);
if (boot_time)
return boot_time;
/* Try to get boot time from the current wtmp file. */
get_boot_time_1 (WTMP_FILE);
get_boot_time_1 (WTMP_FILE, 1);
/* If we did not find a boot time in wtmp, look at wtmp, and so on. */
for (counter = 0; counter < 20 && boot_time == 1; counter++)
for (counter = 0; counter < 20 && ! boot_time; counter++)
{
char cmd_string[100];
Lisp_Object tempname, filename;
@ -206,7 +225,7 @@ get_boot_time ()
if (! NILP (filename))
{
get_boot_time_1 (XSTRING (filename)->data);
get_boot_time_1 (XSTRING (filename)->data, 1);
if (delete_flag)
unlink (XSTRING (filename)->data);
}
@ -221,14 +240,23 @@ get_boot_time ()
#ifdef BOOT_TIME
/* Try to get the boot time from wtmp file FILENAME.
This succeeds if that file contains a reboot record.
Success is indicated by setting BOOT_TIME. */
get_boot_time_1 (filename)
If FILENAME is zero, use the same file as before;
if no FILENAME has ever been specified, this is the utmp file.
Use the newest reboot record if NEWEST is nonzero,
the first reboot record otherwise.
Ignore all reboot records on or before BOOT_TIME.
Success is indicated by setting BOOT_TIME to a larger value. */
get_boot_time_1 (filename, newest)
char *filename;
int newest;
{
struct utmp ut, *utp;
int desc;
if (filename)
{
/* On some versions of IRIX, opening a nonexistent file name
is likely to crash in the utmp routines. */
desc = open (filename, O_RDONLY);
@ -238,7 +266,10 @@ get_boot_time_1 (filename)
close (desc);
utmpname (filename);
}
setutent ();
while (1)
{
/* Find the next reboot record. */
@ -248,7 +279,11 @@ get_boot_time_1 (filename)
break;
/* Compare reboot times and use the newest one. */
if (utp->ut_time > boot_time)
{
boot_time = utp->ut_time;
if (! newest)
break;
}
/* Advance on element in the file
so that getutid won't repeat the same one. */
utp = getutent ();
@ -684,6 +719,7 @@ void
init_filelock ()
{
boot_time = 0;
boot_time_initialized = 0;
}
void