diff options
| -rw-r--r-- | include/linux/backing-dev.h | 4 | ||||
| -rw-r--r-- | include/linux/writeback.h | 4 | ||||
| -rw-r--r-- | kernel/sysctl.c | 2 | ||||
| -rw-r--r-- | mm/backing-dev.c | 19 | ||||
| -rw-r--r-- | mm/page-writeback.c | 203 |
5 files changed, 194 insertions, 38 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 4d9222c..48a62ba 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -10,6 +10,7 @@ #include <linux/percpu_counter.h> #include <linux/log2.h> +#include <linux/proportions.h> #include <asm/atomic.h> struct page; @@ -44,6 +45,9 @@ struct backing_dev_info { void *unplug_io_data; struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS]; + + struct prop_local_percpu completions; + int dirty_exceeded; }; int bdi_init(struct backing_dev_info *bdi); diff --git a/include/linux/writeback.h b/include/linux/writeback.h index d1321a8..52be879 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -97,6 +97,10 @@ extern int dirty_expire_interval; extern int block_dump; extern int laptop_mode; +extern int dirty_ratio_handler(struct ctl_table *table, int write, + struct file *filp, void __user *buffer, size_t *lenp, + loff_t *ppos); + struct ctl_table; struct file; int dirty_writeback_centisecs_handler(struct ctl_table *, int, struct file *, diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 96efbb8..c676b5e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -813,7 +813,7 @@ static ctl_table vm_table[] = { .data = &vm_dirty_ratio, .maxlen = sizeof(vm_dirty_ratio), .mode = 0644, - .proc_handler = &proc_dointvec_minmax, + .proc_handler = &dirty_ratio_handler, .strategy = &sysctl_intvec, .extra1 = &zero, .extra2 = &one_hundred, diff --git a/mm/backing-dev.c b/mm/backing-dev.c index a47065e..b0ceb29 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -12,11 +12,17 @@ int bdi_init(struct backing_dev_info *bdi) for (i = 0; i < NR_BDI_STAT_ITEMS; i++) { err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0); - if (err) { - for (j = 0; j < i; j++) - percpu_counter_destroy(&bdi->bdi_stat[i]); - break; - } + if (err) + goto err; + } + + bdi->dirty_exceeded = 0; + err = prop_local_init_percpu(&bdi->completions); + + if (err) { +err: + for (j = 0; j < i; j++) + percpu_counter_destroy(&bdi->bdi_stat[i]); } return err; @@ -29,6 +35,8 @@ void bdi_destroy(struct backing_dev_info *bdi) for (i = 0; i < NR_BDI_STAT_ITEMS; i++) percpu_counter_destroy(&bdi->bdi_stat[i]); + + prop_local_destroy_percpu(&bdi->completions); } EXPORT_SYMBOL(bdi_destroy); @@ -81,3 +89,4 @@ long congestion_wait(int rw, long timeout) return ret; } EXPORT_SYMBOL(congestion_wait); + diff --git a/mm/page-writeback.c b/mm/page-writeback.c index f1d201f..b036054 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2,6 +2,7 @@ * mm/page-writeback.c * * Copyright (C) 2002, Linus Torvalds. + * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> * * Contains functions related to writing back dirty pages at the * address_space level. @@ -49,8 +50,6 @@ */ static long ratelimit_pages = 32; -static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */ - /* * When balance_dirty_pages decides that the caller needs to perform some * non-background writeback, this is how many pages it will attempt to write. @@ -103,6 +102,103 @@ EXPORT_SYMBOL(laptop_mode); static void background_writeout(unsigned long _min_pages); /* + * Scale the writeback cache size proportional to the relative writeout speeds. + * + * We do this by keeping a floating proportion between BDIs, based on page + * writeback completions [end_page_writeback()]. Those devices that write out + * pages fastest will get the larger share, while the slower will get a smaller + * share. + * + * We use page writeout completions because we are interested in getting rid of + * dirty pages. Having them written out is the primary goal. + * + * We introduce a concept of time, a period over which we measure these events, + * because demand can/will vary over time. The length of this period itself is + * measured in page writeback completions. + * + */ +static struct prop_descriptor vm_completions; + +static unsigned long determine_dirtyable_memory(void); + +/* + * couple the period to the dirty_ratio: + * + * period/2 ~ roundup_pow_of_two(dirty limit) + */ +static int calc_period_shift(void) +{ + unsigned long dirty_total; + + dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 100; + return 2 + ilog2(dirty_total - 1); +} + +/* + * update the period when the dirty ratio changes. + */ +int dirty_ratio_handler(struct ctl_table *table, int write, + struct file *filp, void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + int old_ratio = vm_dirty_ratio; + int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); + if (ret == 0 && write && vm_dirty_ratio != old_ratio) { + int shift = calc_period_shift(); + prop_change_shift(&vm_completions, shift); + } + return ret; +} + +/* + * Increment the BDI's writeout completion count and the global writeout + * completion count. Called from test_clear_page_writeback(). + */ +static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) +{ + __prop_inc_percpu(&vm_completions, &bdi->completions); +} + +/* + * Obtain an accurate fraction of the BDI's portion. + */ +static void bdi_writeout_fraction(struct backing_dev_info *bdi, + long *numerator, long *denominator) +{ + if (bdi_cap_writeback_dirty(bdi)) { + prop_fraction_percpu(&vm_completions, &bdi->completions, + numerator, denominator); + } else { + *numerator = 0; + *denominator = 1; + } +} + +/* + * Clip the earned share of dirty pages to that which is actually available. + * This avoids exceeding the total dirty_limit when the floating averages + * fluctuate too quickly. + */ +static void +clip_bdi_dirty_limit(struct backing_dev_info *bdi, long dirty, long *pbdi_dirty) +{ + long avail_dirty; + + avail_dirty = dirty - + (global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_WRITEBACK) + + global_page_state(NR_UNSTABLE_NFS)); + + if (avail_dirty < 0) + avail_dirty = 0; + + avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) + + bdi_stat(bdi, BDI_WRITEBACK); + + *pbdi_dirty = min(*pbdi_dirty, avail_dirty); +} + +/* * Work out the current dirty-memory clamping and background writeout * thresholds. * @@ -158,8 +254,8 @@ static unsigned long determine_dirtyable_memory(void) } static void -get_dirty_limits(long *pbackground, long *pdirty, - struct address_space *mapping) +get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty, + struct backing_dev_info *bdi) { int background_ratio; /* Percentages */ int dirty_ratio; @@ -193,6 +289,22 @@ get_dirty_limits(long *pbackground, long *pdirty, } *pbackground = background; *pdirty = dirty; + + if (bdi) { + u64 bdi_dirty = dirty; + long numerator, denominator; + + /* + * Calculate this BDI's share of the dirty ratio. + */ + bdi_writeout_fraction(bdi, &numerator, &denominator); + + bdi_dirty *= numerator; + do_div(bdi_dirty, denominator); + + *pbdi_dirty = bdi_dirty; + clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty); + } } /* @@ -204,9 +316,11 @@ get_dirty_limits(long *pbackground, long *pdirty, */ static void balance_dirty_pages(struct address_space *mapping) { - long nr_reclaimable; + long bdi_nr_reclaimable; + long bdi_nr_writeback; long background_thresh; long dirty_thresh; + long bdi_thresh; unsigned long pages_written = 0; unsigned long write_chunk = sync_writeback_pages(); @@ -221,15 +335,15 @@ static void balance_dirty_pages(struct address_space *mapping) .range_cyclic = 1, }; - get_dirty_limits(&background_thresh, &dirty_thresh, mapping); - nr_reclaimable = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= - dirty_thresh) - break; + get_dirty_limits(&background_thresh, &dirty_thresh, + &bdi_thresh, bdi); + bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); + bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); + if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) + break; - if (!dirty_exceeded) - dirty_exceeded = 1; + if (!bdi->dirty_exceeded) + bdi->dirty_exceeded = 1; /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. * Unstable writes are a feature of certain networked @@ -237,26 +351,42 @@ static void balance_dirty_pages(struct address_space *mapping) * written to the server's write cache, but has not yet * been flushed to permanent storage. */ - if (nr_reclaimable) { + if (bdi_nr_reclaimable) { writeback_inodes(&wbc); - get_dirty_limits(&background_thresh, - &dirty_thresh, mapping); - nr_reclaimable = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - if (nr_reclaimable + - global_page_state(NR_WRITEBACK) - <= dirty_thresh) - break; pages_written += write_chunk - wbc.nr_to_write; - if (pages_written >= write_chunk) - break; /* We've done our duty */ + get_dirty_limits(&background_thresh, &dirty_thresh, + &bdi_thresh, bdi); + } + + /* + * In order to avoid the stacked BDI deadlock we need + * to ensure we accurately count the 'dirty' pages when + * the threshold is low. + * + * Otherwise it would be possible to get thresh+n pages + * reported dirty, even though there are thresh-m pages + * actually dirty; with m+n sitting in the percpu + * deltas. + */ + if (bdi_thresh < 2*bdi_stat_error(bdi)) { + bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); + bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); + } else if (bdi_nr_reclaimable) { + bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); + bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); } + + if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) + break; + if (pages_written >= write_chunk) + break; /* We've done our duty */ + congestion_wait(WRITE, HZ/10); } - if (nr_reclaimable + global_page_state(NR_WRITEBACK) - <= dirty_thresh && dirty_exceeded) - dirty_exceeded = 0; + if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh && + bdi->dirty_exceeded) + bdi->dirty_exceeded = 0; if (writeback_in_progress(bdi)) return; /* pdflush is already working this queue */ @@ -270,7 +400,9 @@ static void balance_dirty_pages(struct address_space *mapping) * background_thresh, to keep the amount of dirty memory low. */ if ((laptop_mode && pages_written) || - (!laptop_mode && (nr_reclaimable > background_thresh))) + (!laptop_mode && (global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS) + > background_thresh))) pdflush_operation(background_writeout, 0); } @@ -306,7 +438,7 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, unsigned long *p; ratelimit = ratelimit_pages; - if (dirty_exceeded) + if (mapping->backing_dev_info->dirty_exceeded) ratelimit = 8; /* @@ -342,7 +474,7 @@ void throttle_vm_writeout(gfp_t gfp_mask) } for ( ; ; ) { - get_dirty_limits(&background_thresh, &dirty_thresh, NULL); + get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); /* * Boost the allowable dirty threshold a bit for page @@ -377,7 +509,7 @@ static void background_writeout(unsigned long _min_pages) long background_thresh; long dirty_thresh; - get_dirty_limits(&background_thresh, &dirty_thresh, NULL); + get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); if (global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS) < background_thresh && min_pages <= 0) @@ -580,9 +712,14 @@ static struct notifier_block __cpuinitdata ratelimit_nb = { */ void __init page_writeback_init(void) { + int shift; + mod_timer(&wb_timer, jiffies + dirty_writeback_interval); writeback_set_ratelimit(); register_cpu_notifier(&ratelimit_nb); + + shift = calc_period_shift(); + prop_descriptor_init(&vm_completions, shift); } /** @@ -988,8 +1125,10 @@ int test_clear_page_writeback(struct page *page) radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); - if (bdi_cap_writeback_dirty(bdi)) + if (bdi_cap_writeback_dirty(bdi)) { __dec_bdi_stat(bdi, BDI_WRITEBACK); + __bdi_writeout_inc(bdi); + } } write_unlock_irqrestore(&mapping->tree_lock, flags); } else { |
