Re: "ls -l" command and performance of sftp

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Hi all,

Patch to cache group and userids is attched along with this mail. The patch
looks up the cache first before proceeding with getgrgid,getpwuid calls and
thus reduces the amount of lookups and increases preformance in environments
such as LDAP database.

--
M.P

----- Original Message -----
From: ponraj
To: openssh-unix-dev@mindrot.org
Sent: Saturday, May 06, 2006 10:01 AM
Subject: "ls -l" command and performance of sftp


Hi all,

I am using OpenSSH4.3p2. User database is stored in LDAP server.When I tried
to list about 400 files using "ls -l" command in ftp and sftp, I observed
that sftp took considerable amount of time greater than ftp. I suspect sftp
does not cache the username and groupname lookups and makes fresh calls to
getpwuid(), getgrgid() functions for each file that makes its performance
worse. Any comments ?

--
M.P

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--- sftp-common.c 2006-05-11 22:36:23.000000000 -0700
+++ sftp-common.c_cache 2006-05-11 22:52:54.000000000 -0700
@@ -34,6 +34,9 @@
#include "sftp.h"
#include "sftp-common.h"

+#define GROUP_CACHE_SIZE 5
+#define PW_CACHE_SIZE 5
+
/* Clear contents of attributes structure */
void
attrib_clear(Attrib *a)
@@ -170,6 +173,65 @@
/* NOTREACHED */
}

+struct group* getgrgid_cached(gid_t gid)
+{
+ static struct group *groupcache =3D NULL;
+ struct group *result;
+ int i;
+
+ if (groupcache =3D=3D NULL) {
+ groupcache =3D (struct group *)calloc(GROUP_CACHE_SIZE, =
sizeof(struct group));
+ }
+
+ for (i =3D 0; i < GROUP_CACHE_SIZE; i++) {
+ if (groupcache[i].gr_gid =3D=3D gid && =
groupcache[i].gr_name !=3D NULL) {
+ return &(groupcache[i]);
+ }
+ }
+
+ result =3D getgrgid(gid);
+ if (result !=3D NULL && result->gr_name !=3D NULL) {
+ for (i =3D 0; i < GROUP_CACHE_SIZE; i++) {
+ if (groupcache[i].gr_name =3D=3D NULL) {
+ groupcache[i].gr_gid =3D gid;
+ groupcache[i].gr_name =3D =
strdup(result->gr_name);
+ }
+ }
+ }
+ return result;
+}
+
+struct passwd* getpwuid_cached(uid_t uid)
+{
+ static struct passwd *pwcache =3D NULL;
+ struct passwd *result;
+ int i;
+
+ if (pwcache =3D=3D NULL) {
+ pwcache =3D (struct passwd *)calloc(PW_CACHE_SIZE, =
sizeof(struct passwd));
+ }
+
+ for (i =3D 0; i < PW_CACHE_SIZE; i++) {
+ if (pwcache[i].pw_name !=3D NULL && pwcache[i].pw_uid =
=3D=3D uid) {
+ return &(pwcache[i]);
+ }
+ }
+
+ result =3D getpwuid(uid);
+ if (result !=3D NULL && result->pw_name !=3D NULL) {
+ for (i =3D 0; i < PW_CACHE_SIZE; i++) {
+ if (pwcache[i].pw_name =3D=3D NULL) {
+ pwcache[i].pw_uid =3D uid;
+ pwcache[i].pw_name =3D =
strdup(result->pw_name);
+ }
+ }
+ }
+ return result;
+}
+
+
/*
* drwxr-xr-x 5 markus markus 1024 Jan 13 18:39 .ssh
*/
@@ -184,13 +246,13 @@
char buf[1024], mode[11+1], tbuf[12+1], ubuf[11+1], gbuf[11+1];

strmode(st->st_mode, mode);
- if (!remote && (pw =3D getpwuid(st->st_uid)) !=3D NULL) {
+ if (!remote && (pw =3D getpwuid_cached(st->st_uid)) !=3D NULL) {
user =3D pw->pw_name;
} else {
snprintf(ubuf, sizeof ubuf, "%u", (u_int)st->st_uid);
user =3D ubuf;
}
- if (!remote && (gr =3D getgrgid(st->st_gid)) !=3D NULL) {
+ if (!remote && (gr =3D getgrgid_cached(st->st_gid)) !=3D NULL) {
group =3D gr->gr_name;
} else {
snprintf(gbuf, sizeof gbuf, "%u", (u_int)st->st_gid);

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