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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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c42843f2f0
The start of a heavy weight application (ie. KVM) may instantly knock down determine_dirtyable_memory() if the swap is not enabled or full. global_dirty_limits() and bdi_dirty_limit() will in turn get global/bdi dirty thresholds that are _much_ lower than the global/bdi dirty pages. balance_dirty_pages() will then heavily throttle all dirtiers including the light ones, until the dirty pages drop below the new dirty thresholds. During this _deep_ dirty-exceeded state, the system may appear rather unresponsive to the users. About "deep" dirty-exceeded: task_dirty_limit() assigns 1/8 lower dirty threshold to heavy dirtiers than light ones, and the dirty pages will be throttled around the heavy dirtiers' dirty threshold and reasonably below the light dirtiers' dirty threshold. In this state, only the heavy dirtiers will be throttled and the dirty pages are carefully controlled to not exceed the light dirtiers' dirty threshold. However if the threshold itself suddenly drops below the number of dirty pages, the light dirtiers will get heavily throttled. So introduce global_dirty_limit for tracking the global dirty threshold with policies - follow downwards slowly - follow up in one shot global_dirty_limit can effectively mask out the impact of sudden drop of dirtyable memory. It will be used in the next patch for two new type of dirty limits. Note that the new dirty limits are not going to avoid throttling the light dirtiers, but could limit their sleep time to 200ms. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
162 lines
5.0 KiB
C
162 lines
5.0 KiB
C
/*
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* include/linux/writeback.h
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*/
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#ifndef WRITEBACK_H
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#define WRITEBACK_H
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#include <linux/sched.h>
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#include <linux/fs.h>
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struct backing_dev_info;
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/*
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* fs/fs-writeback.c
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*/
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enum writeback_sync_modes {
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WB_SYNC_NONE, /* Don't wait on anything */
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WB_SYNC_ALL, /* Wait on every mapping */
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};
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/*
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* A control structure which tells the writeback code what to do. These are
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* always on the stack, and hence need no locking. They are always initialised
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* in a manner such that unspecified fields are set to zero.
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*/
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struct writeback_control {
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enum writeback_sync_modes sync_mode;
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long nr_to_write; /* Write this many pages, and decrement
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this for each page written */
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long pages_skipped; /* Pages which were not written */
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/*
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* For a_ops->writepages(): is start or end are non-zero then this is
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* a hint that the filesystem need only write out the pages inside that
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* byterange. The byte at `end' is included in the writeout request.
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*/
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loff_t range_start;
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loff_t range_end;
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unsigned for_kupdate:1; /* A kupdate writeback */
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unsigned for_background:1; /* A background writeback */
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unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
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unsigned for_reclaim:1; /* Invoked from the page allocator */
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unsigned range_cyclic:1; /* range_start is cyclic */
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};
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/*
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* fs/fs-writeback.c
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*/
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struct bdi_writeback;
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int inode_wait(void *);
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void writeback_inodes_sb(struct super_block *);
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void writeback_inodes_sb_nr(struct super_block *, unsigned long nr);
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int writeback_inodes_sb_if_idle(struct super_block *);
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int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr);
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void sync_inodes_sb(struct super_block *);
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long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages);
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long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
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void wakeup_flusher_threads(long nr_pages);
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/* writeback.h requires fs.h; it, too, is not included from here. */
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static inline void wait_on_inode(struct inode *inode)
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{
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might_sleep();
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wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
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}
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static inline void inode_sync_wait(struct inode *inode)
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{
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might_sleep();
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wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
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TASK_UNINTERRUPTIBLE);
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}
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/*
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* mm/page-writeback.c
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*/
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#ifdef CONFIG_BLOCK
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void laptop_io_completion(struct backing_dev_info *info);
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void laptop_sync_completion(void);
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void laptop_mode_sync(struct work_struct *work);
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void laptop_mode_timer_fn(unsigned long data);
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#else
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static inline void laptop_sync_completion(void) { }
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#endif
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void throttle_vm_writeout(gfp_t gfp_mask);
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extern unsigned long global_dirty_limit;
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/* These are exported to sysctl. */
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extern int dirty_background_ratio;
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extern unsigned long dirty_background_bytes;
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extern int vm_dirty_ratio;
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extern unsigned long vm_dirty_bytes;
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extern unsigned int dirty_writeback_interval;
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extern unsigned int dirty_expire_interval;
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extern int vm_highmem_is_dirtyable;
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extern int block_dump;
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extern int laptop_mode;
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extern unsigned long determine_dirtyable_memory(void);
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extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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extern int dirty_ratio_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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extern int dirty_bytes_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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struct ctl_table;
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int dirty_writeback_centisecs_handler(struct ctl_table *, int,
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void __user *, size_t *, loff_t *);
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void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
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unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
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unsigned long dirty);
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void __bdi_update_bandwidth(struct backing_dev_info *bdi,
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unsigned long thresh,
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unsigned long dirty,
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unsigned long bdi_thresh,
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unsigned long bdi_dirty,
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unsigned long start_time);
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void page_writeback_init(void);
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void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
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unsigned long nr_pages_dirtied);
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static inline void
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balance_dirty_pages_ratelimited(struct address_space *mapping)
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{
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balance_dirty_pages_ratelimited_nr(mapping, 1);
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}
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typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
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void *data);
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int generic_writepages(struct address_space *mapping,
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struct writeback_control *wbc);
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void tag_pages_for_writeback(struct address_space *mapping,
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pgoff_t start, pgoff_t end);
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int write_cache_pages(struct address_space *mapping,
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struct writeback_control *wbc, writepage_t writepage,
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void *data);
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int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
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void set_page_dirty_balance(struct page *page, int page_mkwrite);
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void writeback_set_ratelimit(void);
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void tag_pages_for_writeback(struct address_space *mapping,
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pgoff_t start, pgoff_t end);
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/* pdflush.c */
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extern int nr_pdflush_threads; /* Global so it can be exported to sysctl
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read-only. */
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#endif /* WRITEBACK_H */
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