mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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0c9e63fd38
1) Reduce the size of (struct fdtable) to exactly 64 bytes on 32bits platforms, lowering kmalloc() allocated space by 50%. 2) Reduce the size of (files_struct), using a special 32 bits (or 64bits) embedded_fd_set, instead of a 1024 bits fd_set for the close_on_exec_init and open_fds_init fields. This save some ram (248 bytes per task) as most tasks dont open more than 32 files. D-Cache footprint for such tasks is also reduced to the minimum. 3) Reduce size of allocated fdset. Currently two full pages are allocated, that is 32768 bits on x86 for example, and way too much. The minimum is now L1_CACHE_BYTES. UP and SMP should benefit from this patch, because most tasks will touch only one cache line when open()/close() stdin/stdout/stderr (0/1/2), (next_fd, close_on_exec_init, open_fds_init, fd_array[0 .. 2] being in the same cache line) Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
116 lines
2.9 KiB
C
116 lines
2.9 KiB
C
/*
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* Wrapper functions for accessing the file_struct fd array.
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*/
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#ifndef __LINUX_FILE_H
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#define __LINUX_FILE_H
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#include <asm/atomic.h>
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#include <linux/posix_types.h>
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#include <linux/compiler.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/types.h>
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/*
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* The default fd array needs to be at least BITS_PER_LONG,
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* as this is the granularity returned by copy_fdset().
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*/
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#define NR_OPEN_DEFAULT BITS_PER_LONG
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/*
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* The embedded_fd_set is a small fd_set,
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* suitable for most tasks (which open <= BITS_PER_LONG files)
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*/
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struct embedded_fd_set {
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unsigned long fds_bits[1];
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};
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/*
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* More than this number of fds: we use a separately allocated fd_set
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*/
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#define EMBEDDED_FD_SET_SIZE (BITS_PER_BYTE * sizeof(struct embedded_fd_set))
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struct fdtable {
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unsigned int max_fds;
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int max_fdset;
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struct file ** fd; /* current fd array */
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fd_set *close_on_exec;
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fd_set *open_fds;
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struct rcu_head rcu;
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struct files_struct *free_files;
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struct fdtable *next;
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};
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/*
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* Open file table structure
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*/
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struct files_struct {
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/*
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* read mostly part
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*/
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atomic_t count;
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struct fdtable *fdt;
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struct fdtable fdtab;
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/*
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* written part on a separate cache line in SMP
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*/
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spinlock_t file_lock ____cacheline_aligned_in_smp;
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int next_fd;
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struct embedded_fd_set close_on_exec_init;
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struct embedded_fd_set open_fds_init;
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struct file * fd_array[NR_OPEN_DEFAULT];
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};
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#define files_fdtable(files) (rcu_dereference((files)->fdt))
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extern void FASTCALL(__fput(struct file *));
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extern void FASTCALL(fput(struct file *));
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static inline void fput_light(struct file *file, int fput_needed)
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{
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if (unlikely(fput_needed))
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fput(file);
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}
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extern struct file * FASTCALL(fget(unsigned int fd));
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extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
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extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
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extern void put_filp(struct file *);
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extern int get_unused_fd(void);
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extern void FASTCALL(put_unused_fd(unsigned int fd));
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struct kmem_cache;
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extern struct file ** alloc_fd_array(int);
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extern void free_fd_array(struct file **, int);
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extern fd_set *alloc_fdset(int);
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extern void free_fdset(fd_set *, int);
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extern int expand_files(struct files_struct *, int nr);
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extern void free_fdtable(struct fdtable *fdt);
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extern void __init files_defer_init(void);
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static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
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{
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struct file * file = NULL;
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struct fdtable *fdt = files_fdtable(files);
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if (fd < fdt->max_fds)
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file = rcu_dereference(fdt->fd[fd]);
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return file;
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}
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/*
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* Check whether the specified fd has an open file.
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*/
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#define fcheck(fd) fcheck_files(current->files, fd)
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extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
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struct task_struct;
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struct files_struct *get_files_struct(struct task_struct *);
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void FASTCALL(put_files_struct(struct files_struct *fs));
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#endif /* __LINUX_FILE_H */
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