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529bf6be5c
I have benchmarked this on an x86_64 NUMA system and see no significant performance difference on kernbench. Tested on both x86_64 and powerpc. The way we do file struct accounting is not very suitable for batched freeing. For scalability reasons, file accounting was constructor/destructor based. This meant that nr_files was decremented only when the object was removed from the slab cache. This is susceptible to slab fragmentation. With RCU based file structure, consequent batched freeing and a test program like Serge's, we just speed this up and end up with a very fragmented slab - llm22:~ # cat /proc/sys/fs/file-nr 587730 0 758844 At the same time, I see only a 2000+ objects in filp cache. The following patch I fixes this problem. This patch changes the file counting by removing the filp_count_lock. Instead we use a separate percpu counter, nr_files, for now and all accesses to it are through get_nr_files() api. In the sysctl handler for nr_files, we populate files_stat.nr_files before returning to user. Counting files as an when they are created and destroyed (as opposed to inside slab) allows us to correctly count open files with RCU. Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
303 lines
6.7 KiB
C
303 lines
6.7 KiB
C
/*
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* linux/fs/file_table.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
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*/
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#include <linux/config.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/smp_lock.h>
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#include <linux/fs.h>
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#include <linux/security.h>
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#include <linux/eventpoll.h>
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#include <linux/rcupdate.h>
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#include <linux/mount.h>
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#include <linux/capability.h>
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#include <linux/cdev.h>
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#include <linux/fsnotify.h>
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#include <linux/sysctl.h>
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#include <linux/percpu_counter.h>
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#include <asm/atomic.h>
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/* sysctl tunables... */
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struct files_stat_struct files_stat = {
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.max_files = NR_FILE
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};
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/* public. Not pretty! */
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__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
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static struct percpu_counter nr_files __cacheline_aligned_in_smp;
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static inline void file_free_rcu(struct rcu_head *head)
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{
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struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
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kmem_cache_free(filp_cachep, f);
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}
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static inline void file_free(struct file *f)
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{
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percpu_counter_dec(&nr_files);
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call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
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}
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/*
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* Return the total number of open files in the system
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*/
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static int get_nr_files(void)
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{
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return percpu_counter_read_positive(&nr_files);
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}
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/*
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* Return the maximum number of open files in the system
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*/
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int get_max_files(void)
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{
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return files_stat.max_files;
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}
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EXPORT_SYMBOL_GPL(get_max_files);
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/*
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* Handle nr_files sysctl
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*/
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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int proc_nr_files(ctl_table *table, int write, struct file *filp,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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files_stat.nr_files = get_nr_files();
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return proc_dointvec(table, write, filp, buffer, lenp, ppos);
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}
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#else
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int proc_nr_files(ctl_table *table, int write, struct file *filp,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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return -ENOSYS;
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}
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#endif
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/* Find an unused file structure and return a pointer to it.
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* Returns NULL, if there are no more free file structures or
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* we run out of memory.
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*/
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struct file *get_empty_filp(void)
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{
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static int old_max;
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struct file * f;
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/*
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* Privileged users can go above max_files
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*/
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if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
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/*
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* percpu_counters are inaccurate. Do an expensive check before
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* we go and fail.
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*/
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if (percpu_counter_sum(&nr_files) >= files_stat.max_files)
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goto over;
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}
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f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
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if (f == NULL)
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goto fail;
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percpu_counter_inc(&nr_files);
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memset(f, 0, sizeof(*f));
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if (security_file_alloc(f))
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goto fail_sec;
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eventpoll_init_file(f);
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atomic_set(&f->f_count, 1);
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f->f_uid = current->fsuid;
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f->f_gid = current->fsgid;
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rwlock_init(&f->f_owner.lock);
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/* f->f_version: 0 */
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INIT_LIST_HEAD(&f->f_u.fu_list);
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return f;
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over:
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/* Ran out of filps - report that */
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if (get_nr_files() > old_max) {
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printk(KERN_INFO "VFS: file-max limit %d reached\n",
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get_max_files());
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old_max = get_nr_files();
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}
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goto fail;
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fail_sec:
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file_free(f);
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fail:
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return NULL;
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}
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EXPORT_SYMBOL(get_empty_filp);
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void fastcall fput(struct file *file)
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{
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if (atomic_dec_and_test(&file->f_count))
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__fput(file);
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}
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EXPORT_SYMBOL(fput);
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/* __fput is called from task context when aio completion releases the last
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* last use of a struct file *. Do not use otherwise.
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*/
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void fastcall __fput(struct file *file)
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{
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struct dentry *dentry = file->f_dentry;
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struct vfsmount *mnt = file->f_vfsmnt;
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struct inode *inode = dentry->d_inode;
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might_sleep();
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fsnotify_close(file);
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/*
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* The function eventpoll_release() should be the first called
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* in the file cleanup chain.
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*/
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eventpoll_release(file);
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locks_remove_flock(file);
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if (file->f_op && file->f_op->release)
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file->f_op->release(inode, file);
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security_file_free(file);
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if (unlikely(inode->i_cdev != NULL))
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cdev_put(inode->i_cdev);
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fops_put(file->f_op);
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if (file->f_mode & FMODE_WRITE)
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put_write_access(inode);
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file_kill(file);
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file->f_dentry = NULL;
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file->f_vfsmnt = NULL;
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file_free(file);
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dput(dentry);
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mntput(mnt);
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}
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struct file fastcall *fget(unsigned int fd)
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{
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struct file *file;
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struct files_struct *files = current->files;
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rcu_read_lock();
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file = fcheck_files(files, fd);
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if (file) {
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if (!atomic_inc_not_zero(&file->f_count)) {
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/* File object ref couldn't be taken */
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rcu_read_unlock();
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return NULL;
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}
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}
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rcu_read_unlock();
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return file;
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}
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EXPORT_SYMBOL(fget);
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/*
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* Lightweight file lookup - no refcnt increment if fd table isn't shared.
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* You can use this only if it is guranteed that the current task already
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* holds a refcnt to that file. That check has to be done at fget() only
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* and a flag is returned to be passed to the corresponding fput_light().
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* There must not be a cloning between an fget_light/fput_light pair.
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*/
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struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
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{
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struct file *file;
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struct files_struct *files = current->files;
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*fput_needed = 0;
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if (likely((atomic_read(&files->count) == 1))) {
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file = fcheck_files(files, fd);
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} else {
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rcu_read_lock();
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file = fcheck_files(files, fd);
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if (file) {
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if (atomic_inc_not_zero(&file->f_count))
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*fput_needed = 1;
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else
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/* Didn't get the reference, someone's freed */
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file = NULL;
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}
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rcu_read_unlock();
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}
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return file;
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}
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void put_filp(struct file *file)
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{
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if (atomic_dec_and_test(&file->f_count)) {
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security_file_free(file);
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file_kill(file);
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file_free(file);
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}
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}
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void file_move(struct file *file, struct list_head *list)
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{
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if (!list)
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return;
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file_list_lock();
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list_move(&file->f_u.fu_list, list);
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file_list_unlock();
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}
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void file_kill(struct file *file)
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{
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if (!list_empty(&file->f_u.fu_list)) {
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file_list_lock();
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list_del_init(&file->f_u.fu_list);
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file_list_unlock();
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}
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}
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int fs_may_remount_ro(struct super_block *sb)
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{
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struct list_head *p;
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/* Check that no files are currently opened for writing. */
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file_list_lock();
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list_for_each(p, &sb->s_files) {
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struct file *file = list_entry(p, struct file, f_u.fu_list);
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struct inode *inode = file->f_dentry->d_inode;
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/* File with pending delete? */
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if (inode->i_nlink == 0)
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goto too_bad;
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/* Writeable file? */
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if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
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goto too_bad;
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}
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file_list_unlock();
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return 1; /* Tis' cool bro. */
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too_bad:
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file_list_unlock();
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return 0;
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}
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void __init files_init(unsigned long mempages)
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{
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int n;
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/* One file with associated inode and dcache is very roughly 1K.
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* Per default don't use more than 10% of our memory for files.
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*/
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n = (mempages * (PAGE_SIZE / 1024)) / 10;
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files_stat.max_files = n;
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if (files_stat.max_files < NR_FILE)
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files_stat.max_files = NR_FILE;
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files_defer_init();
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percpu_counter_init(&nr_files);
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}
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