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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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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>
97 lines
2.4 KiB
C
97 lines
2.4 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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/*
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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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struct fdtable {
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unsigned int max_fds;
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int max_fdset;
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int next_fd;
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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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atomic_t count;
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struct fdtable *fdt;
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struct fdtable fdtab;
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fd_set close_on_exec_init;
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fd_set open_fds_init;
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struct file * fd_array[NR_OPEN_DEFAULT];
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spinlock_t file_lock; /* Protects concurrent writers. Nests inside tsk->alloc_lock */
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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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