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Date: Wed, 23 Jun 2010 21:56:04 -0500
From: Nathan Fontenot <nfont@...tin.ibm.com>
To: linux-kernel@...r.kernel.org
Subject: [PATCH] Store sysfs dirent structs in rbtree
On very large systems, i.e. those with > 1 TB of memory, the boot times become
exponentially worse due to the string compares used to ensure duplicate sysfs
directories are not created. I am working with systems that create roughly
63,000 memory sections in sysfs at boot time. This translates into just over 9
minutes of creating sysfs entries for the memory on the system at boot. Other
systems have observed 40 minutes for 1.5 TB and times measured in hours for 2
TB systems.
This patch updates the sysfs code to store the sysfs directory entries in a
reb-black tree sorted aphabetically. This significantly reduces the number of
string compares required to determine if a new directory is a duplicate. On
the 1 TB system the sysfs memory creation time went from 9.1 minutes to 2.2
minutes.
Signed-off-by: Nathan Fontenot <nfont@...tin.ibm.com>
---
fs/sysfs/dir.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++-------
fs/sysfs/sysfs.h | 3 ++
2 files changed, 56 insertions(+), 7 deletions(-)
Index: linux-2.6/fs/sysfs/dir.c
===================================================================
--- linux-2.6.orig/fs/sysfs/dir.c 2010-06-23 15:07:22.000000000 -0500
+++ linux-2.6/fs/sysfs/dir.c 2010-06-23 20:12:46.000000000 -0500
@@ -30,6 +30,37 @@
static DEFINE_SPINLOCK(sysfs_ino_lock);
static DEFINE_IDA(sysfs_ino_ida);
+static struct sysfs_dirent *to_sysfs_dirent(struct rb_node *node)
+{
+ struct sysfs_elem_dir *sysdir;
+
+ sysdir = rb_entry(node, struct sysfs_elem_dir, rb_node);
+ return container_of(sysdir, struct sysfs_dirent, s_dir);
+}
+
+static void sysfs_dirent_insert(struct sysfs_dirent *sd)
+{
+ struct sysfs_dirent *parent_sd = sd->s_parent;
+ struct sysfs_dirent *d;
+ struct rb_node **p = &parent_sd->s_dir.rb_root.rb_node;
+ struct rb_node *parent = NULL;
+
+ while (*p) {
+ int cmp_val;
+ parent = *p;
+ d = to_sysfs_dirent(parent);
+
+ cmp_val = strcmp(d->s_name, sd->s_name);
+ if (cmp_val < 0)
+ p = &parent->rb_left;
+ if (cmp_val > 0)
+ p = &parent->rb_right;
+ }
+
+ rb_link_node(&sd->s_dir.rb_node, parent, p);
+ rb_insert_color(&sd->s_dir.rb_node, &parent_sd->s_dir.rb_root);
+}
+
/**
* sysfs_link_sibling - link sysfs_dirent into sibling list
* @sd: sysfs_dirent of interest
@@ -57,6 +88,9 @@
}
sd->s_sibling = *pos;
*pos = sd;
+
+ /* Add entry to rb tree */
+ sysfs_dirent_insert(sd);
}
/**
@@ -81,6 +115,8 @@
break;
}
}
+
+ rb_erase(&sd->s_dir.rb_node, &sd->s_parent->s_dir.rb_root);
}
/**
@@ -536,14 +572,24 @@
const void *ns,
const unsigned char *name)
{
- struct sysfs_dirent *sd;
-
- for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) {
- if (ns && sd->s_ns && (sd->s_ns != ns))
- continue;
- if (!strcmp(sd->s_name, name))
- return sd;
+ struct sysfs_dirent *d;
+ struct rb_node **p = &parent_sd->s_dir.rb_root.rb_node;
+ struct rb_node *parent = NULL;
+
+ while (*p) {
+ int cmp_val;
+ parent = *p;
+ d = to_sysfs_dirent(parent);
+
+ cmp_val = strcmp(d->s_name, name);
+ if (cmp_val == 0)
+ return d;
+ else if (cmp_val < 0)
+ p = &parent->rb_left;
+ else /* (cmp_val > 0) */
+ p = &parent->rb_right;
}
+
return NULL;
}
Index: linux-2.6/fs/sysfs/sysfs.h
===================================================================
--- linux-2.6.orig/fs/sysfs/sysfs.h 2010-06-23 15:07:22.000000000 -0500
+++ linux-2.6/fs/sysfs/sysfs.h 2010-06-23 20:12:46.000000000 -0500
@@ -10,12 +10,15 @@
#include <linux/lockdep.h>
#include <linux/fs.h>
+#include <linux/rbtree.h>
struct sysfs_open_dirent;
/* type-specific structures for sysfs_dirent->s_* union members */
struct sysfs_elem_dir {
struct kobject *kobj;
+ struct rb_root rb_root;
+ struct rb_node rb_node;
/* children list starts here and goes through sd->s_sibling */
struct sysfs_dirent *children;
};
--
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