bin/51148: Control the cache size for pwd_mkdb to speedup vipw

[Alex Semenyaka]

>Number:         51148
>Category:       bin
>Synopsis:       Control the cache size for pwd_mkdb to speedup vipw
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Fri Apr 18 21:30:11 PDT 2003
>Closed-Date:
>Last-Modified:
>Originator:     Alex Semenyaka
>Release:        FreeBSD 4.8-RC i386
>Organization:
Ratmir
>Environment:

FIRST:
FreeBSD home.rinet.ru 4.8-RELEASE FreeBSD 4.8-RELEASE #2: Tue Apr  1 20:54:29 MSD 2003     marck at kucha.rinet.ru:/usr/obj/FreeBSD/src.stable-48/sys/home  i386

CPU: AMD Duron(tm) Processor  (601.37-MHz 686-class CPU)
  Origin = "AuthenticAMD"  Id = 0x630  Stepping = 0
  Features=0x183f9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR>
  AMD Features=0xc0440000<RSVD,AMIE,DSP,3DNow!>
real memory  = 134152192 (131008K bytes)
avail memory = 127193088 (124212K bytes)

SECOND:
FreeBSD snark.ratmir.ru 4.8-RC FreeBSD 4.8-RC #7: Sun Mar 30 07:23:48 MSD 2003 root at snark.ratmir.ru:/usr/obj/usr/src/sys/SNARK  i386

CPU: Intel Pentium III (1002.28-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0x68a  Stepping = 10
  Features=0x387f9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,PN,MMX,FXSR,SSE>
real memory  = 268435456 (262144K bytes)
avail memory = 256475136 (250464K bytes)


>Description:

There are some FreeBSD boxes which have really huge master.passwd files
since we have no nss under 4.x and, thus, all users should be listed there
for a lot of programs. The host is described as FIRST above is the mailboxes
and homepages storage for the all users of some ISP in Moscow, Russia. It holds
above the 10000 lines in the master.passwd.

There is an option for pwd_mkdb which allows to set the size of cache when
database is opened (-s <cache size in Ms>). That helps sufficiently increase
the speed of database rebuilding. But there no way to use this option with
the pw_mkdb() function, shipped with vipw in 4.x and moved to libutil in
CURRENT. That function execs pwd_mkdb with options -p -d <dir>, and
optionally with -u <user>. Vipw (and maybe some other programs in -CURRENT)
just uses the call to pw_mkdb(). So there is no way for vipw to set somehow
the cache size to be used in pwd_mkdb while it can be very useful.

Some data for the real host are given below ("uname -a" output and the dmesg
part about the processor and memory see above, marked as FIRST). I measured
the time necessary for the pwd_mkdb to rebuild master.passwd database with
the same arguments as used in pw_mkdb() with the "-s" option added. Here are
results:

cache sized		total time to run
passed with -s

   1			1m1.434s
   2			0m32.604s
   4			0m3.550s
   8			0m2.792s
   12			0m2.749s
   16			0m2.528s

bash-2.05b# wc -l master.passwd
   10021 master.passwd

Default value of the cache size is 2M. As you can see it can cause very
slow execution of pwd_mkdb.

The next one - data for the another computer (data are given above under the
SECOND label), here master.passwd are generated artificially:

cache sized		total time to run
passed with -s

   2			2m54.342s
   4			2m18.354s
   8			0m39.987s
   12			0m10.734s
   16			0m7.535s
   24			0m7.469s
   32			0m7.728s

bash-2.05b# wc -l master.passwd
   37038 master.passwd

Now, even 8M is not enough.

>How-To-Repeat:

Create a really big (10000-20000-... records) master.passwd file and run

#pwd_mkdb -p -s N -d /etc master.passwd

where N is 2 to 16.

>Fix:

I suggest to pass the value of the cache size through the environment 
variable. I called it PWDB_CACHE. By default the behaviour of pkd_mkdb
and all programs those can inherit the problem does not change. But if
system administrator needs to increase the speed of the users db rebuilding
it just can set PWDB_CACHE to some value greater than 2 (2M is build-in
default) and enjoy. As in command-line the unit is megabyte.

Here is the patch:

diff -r -u ../pwd_mkdb/pwd_mkdb.c ./pwd_mkdb.c
--- ../pwd_mkdb/pwd_mkdb.c	Fri Jul 12 01:16:52 2002
+++ ./pwd_mkdb.c	Sat Apr 19 07:31:52 2003
@@ -66,14 +66,17 @@
 #define	SECURE		2
 #define	PERM_INSECURE	(S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH)
 #define	PERM_SECURE	(S_IRUSR|S_IWUSR)
+#define	MINCACHE	2
+#define	MAXCACHE	16
+#define	CACHESZ_ENV	"PWDB_CACHE"
 
 HASHINFO openinfo = {
-	4096,		/* bsize */
-	32,		/* ffactor */
-	256,		/* nelem */
-	2048 * 1024,	/* cachesize */
-	NULL,		/* hash() */
-	0		/* lorder */
+	4096,			/* bsize */
+	32,			/* ffactor */
+	256,			/* nelem */
+	MINCACHE * 1024 * 1024,	/* cachesize */
+	NULL,			/* hash() */
+	0			/* lorder */
 };
 
 static enum state { FILE_INSECURE, FILE_SECURE, FILE_ORIG } clean;
@@ -101,6 +104,8 @@
 	int ch, cnt, ypcnt, makeold, tfd, yp_enabled = 0;
 	unsigned int len;
 	int32_t pw_change, pw_expire;
+	int cache;
+	char *penv;
 	const char *t;
 	char *p;
 	char buf[MAX(MAXPATHLEN, LINE_MAX * 2)], tbuf[1024];
@@ -116,6 +121,17 @@
 	strcpy(prefix, _PATH_PWD);
 	makeold = 0;
 	username = NULL;
+
+	penv = getenv(CACHESZ_ENV);
+	if (penv != NULL) {
+		cache = atoi(penv);
+		if (cache < MINCACHE)
+			cache = MINCACHE;
+		if (cache > MAXCACHE)
+			cache = MAXCACHE;
+		openinfo.cachesize = cache * 1024 * 1024;
+	}
+
 	while ((ch = getopt(argc, argv, "Cd:ps:u:vN")) != -1)
 		switch(ch) {
 		case 'C':                       /* verify only */
>Release-Note:
>Audit-Trail:
>Unformatted: