6a15a37097
The previous patch has improved swap accounting for shmem mapping, which however made /proc/pid/smaps more expensive for shmem mappings, as we consult the radix tree for each pte_none entry, so the overal complexity is O(n*log(n)). We can reduce this significantly for mappings that cannot contain COWed pages, because then we can either use the statistics tha shmem object itself tracks (if the mapping contains the whole object, or the swap usage of the whole object is zero), or use the radix tree iterator, which is much more effective than repeated find_get_entry() calls. This patch therefore introduces a function shmem_swap_usage(vma) and makes /proc/pid/smaps use it when possible. Only for writable private mappings of shmem objects (i.e. tmpfs files) with the shmem object itself (partially) swapped outwe have to resort to the find_get_entry() approach. Hopefully such mappings are relatively uncommon. To demonstrate the diference, I have measured this on a process that creates a 2GB mapping and dirties single pages with a stride of 2MB, and time how long does it take to cat /proc/pid/smaps of this process 100 times. Private writable mapping of a /dev/shm/file (the most complex case): real 0m3.831s user 0m0.180s sys 0m3.212s Shared mapping of an almost full mapping of a partially swapped /dev/shm/file (which needs to employ the radix tree iterator). real 0m1.351s user 0m0.096s sys 0m0.768s Same, but with /dev/shm/file not swapped (so no radix tree walk needed) real 0m0.935s user 0m0.128s sys 0m0.344s Private anonymous mapping: real 0m0.949s user 0m0.116s sys 0m0.348s The cost is now much closer to the private anonymous mapping case, unless the shmem mapping is private and writable. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
88 lines
2.9 KiB
C
88 lines
2.9 KiB
C
#ifndef __SHMEM_FS_H
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#define __SHMEM_FS_H
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#include <linux/file.h>
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#include <linux/swap.h>
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#include <linux/mempolicy.h>
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#include <linux/pagemap.h>
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#include <linux/percpu_counter.h>
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#include <linux/xattr.h>
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/* inode in-kernel data */
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struct shmem_inode_info {
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spinlock_t lock;
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unsigned int seals; /* shmem seals */
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unsigned long flags;
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unsigned long alloced; /* data pages alloced to file */
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union {
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unsigned long swapped; /* subtotal assigned to swap */
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char *symlink; /* unswappable short symlink */
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};
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struct shared_policy policy; /* NUMA memory alloc policy */
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struct list_head swaplist; /* chain of maybes on swap */
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struct simple_xattrs xattrs; /* list of xattrs */
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struct inode vfs_inode;
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};
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struct shmem_sb_info {
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unsigned long max_blocks; /* How many blocks are allowed */
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struct percpu_counter used_blocks; /* How many are allocated */
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unsigned long max_inodes; /* How many inodes are allowed */
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unsigned long free_inodes; /* How many are left for allocation */
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spinlock_t stat_lock; /* Serialize shmem_sb_info changes */
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kuid_t uid; /* Mount uid for root directory */
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kgid_t gid; /* Mount gid for root directory */
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umode_t mode; /* Mount mode for root directory */
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struct mempolicy *mpol; /* default memory policy for mappings */
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};
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static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
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{
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return container_of(inode, struct shmem_inode_info, vfs_inode);
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}
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/*
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* Functions in mm/shmem.c called directly from elsewhere:
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*/
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extern int shmem_init(void);
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extern int shmem_fill_super(struct super_block *sb, void *data, int silent);
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extern struct file *shmem_file_setup(const char *name,
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loff_t size, unsigned long flags);
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extern struct file *shmem_kernel_file_setup(const char *name, loff_t size,
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unsigned long flags);
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extern int shmem_zero_setup(struct vm_area_struct *);
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extern int shmem_lock(struct file *file, int lock, struct user_struct *user);
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extern bool shmem_mapping(struct address_space *mapping);
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extern void shmem_unlock_mapping(struct address_space *mapping);
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extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
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pgoff_t index, gfp_t gfp_mask);
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extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
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extern int shmem_unuse(swp_entry_t entry, struct page *page);
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extern unsigned long shmem_swap_usage(struct vm_area_struct *vma);
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static inline struct page *shmem_read_mapping_page(
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struct address_space *mapping, pgoff_t index)
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{
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return shmem_read_mapping_page_gfp(mapping, index,
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mapping_gfp_mask(mapping));
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}
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#ifdef CONFIG_TMPFS
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extern int shmem_add_seals(struct file *file, unsigned int seals);
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extern int shmem_get_seals(struct file *file);
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extern long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg);
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#else
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static inline long shmem_fcntl(struct file *f, unsigned int c, unsigned long a)
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{
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return -EINVAL;
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}
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#endif
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#endif
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