Under normal circumstances each device is given a part of the total write-back cache that relates to its current avg writeout speed in relation to the other devices. min_ratio - allows one to assign a minimum portion of the write-back cache to a particular device. This is useful in situations where you might want to provide a minimum QoS. (One request for this feature came from flash based storage people who wanted to avoid writing out at all costs - they of course needed some pdflush hacks as well) max_ratio - allows one to assign a maximum portion of the dirty limit to a particular device. This is useful in situations where you want to avoid one device taking all or most of the write-back cache. Eg. an NFS mount that is prone to get stuck, or a FUSE mount which you don't trust to play fair. Add "min_ratio" to /sys/class/bdi. This indicates the minimum percentage of the global dirty threshold allocated to this bdi. [mszeredi@suse.cz] - fix parsing in min_ratio_store() - document new sysfs attribute
Unified · Split
| @@ -44,3 +44,9 @@ bdi_dirty_kb (read-only) · 43 unmodified lines | ||
| 44 | 44 | Current threshold on this BDI for reclaimable + writeback |
| 45 | 45 | memory |
| 46 | 46 | |
| 47 | +min_ratio (read-write) | |
| 48 | + | |
| 49 | + Minimal percentage of global dirty threshold allocated to this | |
| 50 | + bdi. If the value written to this file would make the the sum | |
| 51 | + of all min_ratio values exceed 100, then EINVAL is returned. | |
| 52 | + The default is zero | |
| @@ -51,6 +51,8 @@ struct backing_dev_info { · 50 unmodified lines | ||
| 51 | 51 | struct prop_local_percpu completions; |
| 52 | 52 | int dirty_exceeded; |
| 53 | 53 | |
| 54 | + unsigned int min_ratio; | |
| 55 | + | |
| 54 | 56 | struct device *dev; |
| 55 | 57 | }; |
| 56 | 58 | |
| @@ -137,6 +139,8 @@ static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi) · 80 unmodified lines | ||
| 137 | 139 | #endif |
| 138 | 140 | } |
| 139 | 141 | |
| 142 | +int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); | |
| 143 | + | |
| 140 | 144 | /* |
| 141 | 145 | * Flags in backing_dev_info::capability |
| 142 | 146 | * - The first two flags control whether dirty pages will contribute to the |
| @@ -55,6 +55,24 @@ static inline unsigned long get_dirty(struct backing_dev_info *bdi, int i) · 54 unmodified lines | ||
| 55 | 55 | BDI_SHOW(dirty_kb, K(get_dirty(bdi, 1))) |
| 56 | 56 | BDI_SHOW(bdi_dirty_kb, K(get_dirty(bdi, 2))) |
| 57 | 57 | |
| 58 | +static ssize_t min_ratio_store(struct device *dev, | |
| 59 | + struct device_attribute *attr, const char *buf, size_t count) | |
| 60 | +{ | |
| 61 | + struct backing_dev_info *bdi = dev_get_drvdata(dev); | |
| 62 | + char *end; | |
| 63 | + unsigned int ratio; | |
| 64 | + ssize_t ret = -EINVAL; | |
| 65 | + | |
| 66 | + ratio = simple_strtoul(buf, &end, 10); | |
| 67 | + if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { | |
| 68 | + ret = bdi_set_min_ratio(bdi, ratio); | |
| 69 | + if (!ret) | |
| 70 | + ret = count; | |
| 71 | + } | |
| 72 | + return ret; | |
| 73 | +} | |
| 74 | +BDI_SHOW(min_ratio, bdi->min_ratio) | |
| 75 | + | |
| 58 | 76 | #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store) |
| 59 | 77 | |
| 60 | 78 | static struct device_attribute bdi_dev_attrs[] = { |
| @@ -63,6 +81,7 @@ static struct device_attribute bdi_dev_attrs[] = { · 2 unmodified lines | ||
| 63 | 81 | __ATTR_RO(writeback_kb), |
| 64 | 82 | __ATTR_RO(dirty_kb), |
| 65 | 83 | __ATTR_RO(bdi_dirty_kb), |
| 84 | + __ATTR_RW(min_ratio), | |
| 66 | 85 | __ATTR_NULL, |
| 67 | 86 | }; |
| 68 | 87 | |
| @@ -127,6 +146,8 @@ int bdi_init(struct backing_dev_info *bdi) · 58 unmodified lines | ||
| 127 | 146 | |
| 128 | 147 | bdi->dev = NULL; |
| 129 | 148 | |
| 149 | + bdi->min_ratio = 0; | |
| 150 | + | |
| 130 | 151 | for (i = 0; i < NR_BDI_STAT_ITEMS; i++) { |
| 131 | 152 | err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0); |
| 132 | 153 | if (err) |
| @@ -242,6 +242,29 @@ static void task_dirty_limit(struct task_struct *tsk, long *pdirty) · 241 unmodified lines | ||
| 242 | 242 | *pdirty = dirty; |
| 243 | 243 | } |
| 244 | 244 | |
| 245 | +/* | |
| 246 | + * | |
| 247 | + */ | |
| 248 | +static DEFINE_SPINLOCK(bdi_lock); | |
| 249 | +static unsigned int bdi_min_ratio; | |
| 250 | + | |
| 251 | +int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
| 252 | +{ | |
| 253 | + int ret = 0; | |
| 254 | + unsigned long flags; | |
| 255 | + | |
| 256 | + spin_lock_irqsave(&bdi_lock, flags); | |
| 257 | + min_ratio -= bdi->min_ratio; | |
| 258 | + if (bdi_min_ratio + min_ratio < 100) { | |
| 259 | + bdi_min_ratio += min_ratio; | |
| 260 | + bdi->min_ratio += min_ratio; | |
| 261 | + } else | |
| 262 | + ret = -EINVAL; | |
| 263 | + spin_unlock_irqrestore(&bdi_lock, flags); | |
| 264 | + | |
| 265 | + return ret; | |
| 266 | +} | |
| 267 | + | |
| 245 | 268 | /* |
| 246 | 269 | * Work out the current dirty-memory clamping and background writeout |
| 247 | 270 | * thresholds. |
| @@ -330,7 +353,7 @@ get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty, · 82 unmodified lines | ||
| 330 | 353 | *pdirty = dirty; |
| 331 | 354 | |
| 332 | 355 | if (bdi) { |
| 333 | − u64 bdi_dirty = dirty; | |
| 356 | + u64 bdi_dirty; | |
| 334 | 357 | long numerator, denominator; |
| 335 | 358 | |
| 336 | 359 | /* |
| @@ -338,8 +361,10 @@ get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty, · 1 unmodified line | ||
| 338 | 361 | */ |
| 339 | 362 | bdi_writeout_fraction(bdi, &numerator, &denominator); |
| 340 | 363 | |
| 364 | + bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; | |
| 341 | 365 | bdi_dirty *= numerator; |
| 342 | 366 | do_div(bdi_dirty, denominator); |
| 367 | + bdi_dirty += (dirty * bdi->min_ratio) / 100; | |
| 343 | 368 | |
| 344 | 369 | *pbdi_dirty = bdi_dirty; |
| 345 | 370 | clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty); |