*
* (o) global/bdi setpoints
*
- * We want the dirty pages be balanced around the global/bdi setpoints.
+ * We want the dirty pages be balanced around the global/wb setpoints.
* When the number of dirty pages is higher/lower than the setpoint, the
* dirty position control ratio (and hence task dirty ratelimit) will be
* decreased/increased to bring the dirty pages back to the setpoint.
* if (dirty < setpoint) scale up pos_ratio
* if (dirty > setpoint) scale down pos_ratio
*
- * if (bdi_dirty < bdi_setpoint) scale up pos_ratio
- * if (bdi_dirty > bdi_setpoint) scale down pos_ratio
+ * if (wb_dirty < wb_setpoint) scale up pos_ratio
+ * if (wb_dirty > wb_setpoint) scale down pos_ratio
*
* task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT
*
* 0 +------------.------------------.----------------------*------------->
* freerun^ setpoint^ limit^ dirty pages
*
- * (o) bdi control line
+ * (o) wb control line
*
* ^ pos_ratio
* |
* | . .
* | . .
* 0 +----------------------.-------------------------------.------------->
- * bdi_setpoint^ x_intercept^
+ * wb_setpoint^ x_intercept^
*
- * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can
+ * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can
* be smoothly throttled down to normal if it starts high in situations like
* - start writing to a slow SD card and a fast disk at the same time. The SD
- * card's bdi_dirty may rush to many times higher than bdi_setpoint.
- * - the bdi dirty thresh drops quickly due to change of JBOD workload
+ * card's wb_dirty may rush to many times higher than wb_setpoint.
+ * - the wb dirty thresh drops quickly due to change of JBOD workload
*/
static unsigned long wb_position_ratio(struct bdi_writeback *wb,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
- unsigned long bdi_thresh,
- unsigned long bdi_dirty)
+ unsigned long wb_thresh,
+ unsigned long wb_dirty)
{
unsigned long write_bw = wb->avg_write_bandwidth;
unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
unsigned long limit = hard_dirty_limit(thresh);
unsigned long x_intercept;
unsigned long setpoint; /* dirty pages' target balance point */
- unsigned long bdi_setpoint;
+ unsigned long wb_setpoint;
unsigned long span;
long long pos_ratio; /* for scaling up/down the rate limit */
long x;
/*
* The strictlimit feature is a tool preventing mistrusted filesystems
* from growing a large number of dirty pages before throttling. For
- * such filesystems balance_dirty_pages always checks bdi counters
- * against bdi limits. Even if global "nr_dirty" is under "freerun".
+ * such filesystems balance_dirty_pages always checks wb counters
+ * against wb limits. Even if global "nr_dirty" is under "freerun".
* This is especially important for fuse which sets bdi->max_ratio to
* 1% by default. Without strictlimit feature, fuse writeback may
* consume arbitrary amount of RAM because it is accounted in
* NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty".
*
* Here, in wb_position_ratio(), we calculate pos_ratio based on
- * two values: bdi_dirty and bdi_thresh. Let's consider an example:
+ * two values: wb_dirty and wb_thresh. Let's consider an example:
* total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global
* limits are set by default to 10% and 20% (background and throttle).
- * Then bdi_thresh is 1% of 20% of 16GB. This amounts to ~8K pages.
- * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. bdi_setpoint is
- * about ~6K pages (as the average of background and throttle bdi
+ * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages.
+ * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. wb_setpoint is
+ * about ~6K pages (as the average of background and throttle wb
* limits). The 3rd order polynomial will provide positive feedback if
- * bdi_dirty is under bdi_setpoint and vice versa.
+ * wb_dirty is under wb_setpoint and vice versa.
*
* Note, that we cannot use global counters in these calculations
- * because we want to throttle process writing to a strictlimit BDI
+ * because we want to throttle process writing to a strictlimit wb
* much earlier than global "freerun" is reached (~23MB vs. ~2.3GB
* in the example above).
*/
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
- long long bdi_pos_ratio;
- unsigned long bdi_bg_thresh;
+ long long wb_pos_ratio;
+ unsigned long wb_bg_thresh;
- if (bdi_dirty < 8)
+ if (wb_dirty < 8)
return min_t(long long, pos_ratio * 2,
2 << RATELIMIT_CALC_SHIFT);
- if (bdi_dirty >= bdi_thresh)
+ if (wb_dirty >= wb_thresh)
return 0;
- bdi_bg_thresh = div_u64((u64)bdi_thresh * bg_thresh, thresh);
- bdi_setpoint = dirty_freerun_ceiling(bdi_thresh,
- bdi_bg_thresh);
+ wb_bg_thresh = div_u64((u64)wb_thresh * bg_thresh, thresh);
+ wb_setpoint = dirty_freerun_ceiling(wb_thresh, wb_bg_thresh);
- if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh)
+ if (wb_setpoint == 0 || wb_setpoint == wb_thresh)
return 0;
- bdi_pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty,
- bdi_thresh);
+ wb_pos_ratio = pos_ratio_polynom(wb_setpoint, wb_dirty,
+ wb_thresh);
/*
- * Typically, for strictlimit case, bdi_setpoint << setpoint
- * and pos_ratio >> bdi_pos_ratio. In the other words global
+ * Typically, for strictlimit case, wb_setpoint << setpoint
+ * and pos_ratio >> wb_pos_ratio. In the other words global
* state ("dirty") is not limiting factor and we have to
- * make decision based on bdi counters. But there is an
+ * make decision based on wb counters. But there is an
* important case when global pos_ratio should get precedence:
* global limits are exceeded (e.g. due to activities on other
- * BDIs) while given strictlimit BDI is below limit.
+ * wb's) while given strictlimit wb is below limit.
*
- * "pos_ratio * bdi_pos_ratio" would work for the case above,
+ * "pos_ratio * wb_pos_ratio" would work for the case above,
* but it would look too non-natural for the case of all
- * activity in the system coming from a single strictlimit BDI
+ * activity in the system coming from a single strictlimit wb
* with bdi->max_ratio == 100%.
*
* Note that min() below somewhat changes the dynamics of the
* control system. Normally, pos_ratio value can be well over 3
- * (when globally we are at freerun and bdi is well below bdi
+ * (when globally we are at freerun and wb is well below wb
* setpoint). Now the maximum pos_ratio in the same situation
* is 2. We might want to tweak this if we observe the control
* system is too slow to adapt.
*/
- return min(pos_ratio, bdi_pos_ratio);
+ return min(pos_ratio, wb_pos_ratio);
}
/*
* We have computed basic pos_ratio above based on global situation. If
- * the bdi is over/under its share of dirty pages, we want to scale
+ * the wb is over/under its share of dirty pages, we want to scale
* pos_ratio further down/up. That is done by the following mechanism.
*/
/*
- * bdi setpoint
+ * wb setpoint
*
- * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
+ * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint)
*
- * x_intercept - bdi_dirty
+ * x_intercept - wb_dirty
* := --------------------------
- * x_intercept - bdi_setpoint
+ * x_intercept - wb_setpoint
*
- * The main bdi control line is a linear function that subjects to
+ * The main wb control line is a linear function that subjects to
*
- * (1) f(bdi_setpoint) = 1.0
- * (2) k = - 1 / (8 * write_bw) (in single bdi case)
- * or equally: x_intercept = bdi_setpoint + 8 * write_bw
+ * (1) f(wb_setpoint) = 1.0
+ * (2) k = - 1 / (8 * write_bw) (in single wb case)
+ * or equally: x_intercept = wb_setpoint + 8 * write_bw
*
- * For single bdi case, the dirty pages are observed to fluctuate
+ * For single wb case, the dirty pages are observed to fluctuate
* regularly within range
- * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
+ * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2]
* for various filesystems, where (2) can yield in a reasonable 12.5%
* fluctuation range for pos_ratio.
*
- * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its
+ * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its
* own size, so move the slope over accordingly and choose a slope that
- * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh.
+ * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh.
*/
- if (unlikely(bdi_thresh > thresh))
- bdi_thresh = thresh;
+ if (unlikely(wb_thresh > thresh))
+ wb_thresh = thresh;
/*
- * It's very possible that bdi_thresh is close to 0 not because the
+ * It's very possible that wb_thresh is close to 0 not because the
* device is slow, but that it has remained inactive for long time.
* Honour such devices a reasonable good (hopefully IO efficient)
* threshold, so that the occasional writes won't be blocked and active
* writes can rampup the threshold quickly.
*/
- bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
+ wb_thresh = max(wb_thresh, (limit - dirty) / 8);
/*
- * scale global setpoint to bdi's:
- * bdi_setpoint = setpoint * bdi_thresh / thresh
+ * scale global setpoint to wb's:
+ * wb_setpoint = setpoint * wb_thresh / thresh
*/
- x = div_u64((u64)bdi_thresh << 16, thresh + 1);
- bdi_setpoint = setpoint * (u64)x >> 16;
+ x = div_u64((u64)wb_thresh << 16, thresh + 1);
+ wb_setpoint = setpoint * (u64)x >> 16;
/*
- * Use span=(8*write_bw) in single bdi case as indicated by
- * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
+ * Use span=(8*write_bw) in single wb case as indicated by
+ * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case.
*
- * bdi_thresh thresh - bdi_thresh
- * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
- * thresh thresh
+ * wb_thresh thresh - wb_thresh
+ * span = --------- * (8 * write_bw) + ------------------ * wb_thresh
+ * thresh thresh
*/
- span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
- x_intercept = bdi_setpoint + span;
+ span = (thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16;
+ x_intercept = wb_setpoint + span;
- if (bdi_dirty < x_intercept - span / 4) {
- pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty),
- x_intercept - bdi_setpoint + 1);
+ if (wb_dirty < x_intercept - span / 4) {
+ pos_ratio = div64_u64(pos_ratio * (x_intercept - wb_dirty),
+ x_intercept - wb_setpoint + 1);
} else
pos_ratio /= 4;
/*
- * bdi reserve area, safeguard against dirty pool underrun and disk idle
+ * wb reserve area, safeguard against dirty pool underrun and disk idle
* It may push the desired control point of global dirty pages higher
* than setpoint.
*/
- x_intercept = bdi_thresh / 2;
- if (bdi_dirty < x_intercept) {
- if (bdi_dirty > x_intercept / 8)
- pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
+ x_intercept = wb_thresh / 2;
+ if (wb_dirty < x_intercept) {
+ if (wb_dirty > x_intercept / 8)
+ pos_ratio = div_u64(pos_ratio * x_intercept, wb_dirty);
else
pos_ratio *= 8;
}
}
/*
- * Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
+ * Maintain wb->dirty_ratelimit, the base dirty throttle rate.
*
- * Normal bdi tasks will be curbed at or below it in long term.
+ * Normal wb tasks will be curbed at or below it in long term.
* Obviously it should be around (write_bw / N) when there are N dd tasks.
*/
static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
- unsigned long bdi_thresh,
- unsigned long bdi_dirty,
+ unsigned long wb_thresh,
+ unsigned long wb_dirty,
unsigned long dirtied,
unsigned long elapsed)
{
dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed;
pos_ratio = wb_position_ratio(wb, thresh, bg_thresh, dirty,
- bdi_thresh, bdi_dirty);
+ wb_thresh, wb_dirty);
/*
* task_ratelimit reflects each dd's dirty rate for the past 200ms.
*/
/*
* A linear estimation of the "balanced" throttle rate. The theory is,
- * if there are N dd tasks, each throttled at task_ratelimit, the bdi's
+ * if there are N dd tasks, each throttled at task_ratelimit, the wb's
* dirty_rate will be measured to be (N * task_ratelimit). So the below
* formula will yield the balanced rate limit (write_bw / N).
*
/*
* We could safely do this and return immediately:
*
- * bdi->dirty_ratelimit = balanced_dirty_ratelimit;
+ * wb->dirty_ratelimit = balanced_dirty_ratelimit;
*
* However to get a more stable dirty_ratelimit, the below elaborated
* code makes use of task_ratelimit to filter out singular points and
step = 0;
/*
- * For strictlimit case, calculations above were based on bdi counters
+ * For strictlimit case, calculations above were based on wb counters
* and limits (starting from pos_ratio = wb_position_ratio() and up to
* balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate).
- * Hence, to calculate "step" properly, we have to use bdi_dirty as
- * "dirty" and bdi_setpoint as "setpoint".
+ * Hence, to calculate "step" properly, we have to use wb_dirty as
+ * "dirty" and wb_setpoint as "setpoint".
*
- * We rampup dirty_ratelimit forcibly if bdi_dirty is low because
- * it's possible that bdi_thresh is close to zero due to inactivity
+ * We rampup dirty_ratelimit forcibly if wb_dirty is low because
+ * it's possible that wb_thresh is close to zero due to inactivity
* of backing device (see the implementation of wb_dirty_limit()).
*/
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
- dirty = bdi_dirty;
- if (bdi_dirty < 8)
- setpoint = bdi_dirty + 1;
+ dirty = wb_dirty;
+ if (wb_dirty < 8)
+ setpoint = wb_dirty + 1;
else
- setpoint = (bdi_thresh +
+ setpoint = (wb_thresh +
wb_dirty_limit(wb, bg_thresh)) / 2;
}
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
- unsigned long bdi_thresh,
- unsigned long bdi_dirty,
+ unsigned long wb_thresh,
+ unsigned long wb_dirty,
unsigned long start_time)
{
unsigned long now = jiffies;
if (thresh) {
global_update_bandwidth(thresh, dirty, now);
wb_update_dirty_ratelimit(wb, thresh, bg_thresh, dirty,
- bdi_thresh, bdi_dirty,
+ wb_thresh, wb_dirty,
dirtied, elapsed);
}
wb_update_write_bandwidth(wb, elapsed, written);
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
- unsigned long bdi_thresh,
- unsigned long bdi_dirty,
+ unsigned long wb_thresh,
+ unsigned long wb_dirty,
unsigned long start_time)
{
if (time_is_after_eq_jiffies(wb->bw_time_stamp + BANDWIDTH_INTERVAL))
return;
spin_lock(&wb->list_lock);
__wb_update_bandwidth(wb, thresh, bg_thresh, dirty,
- bdi_thresh, bdi_dirty, start_time);
+ wb_thresh, wb_dirty, start_time);
spin_unlock(&wb->list_lock);
}
}
static unsigned long wb_max_pause(struct bdi_writeback *wb,
- unsigned long bdi_dirty)
+ unsigned long wb_dirty)
{
unsigned long bw = wb->avg_write_bandwidth;
unsigned long t;
*
* 8 serves as the safety ratio.
*/
- t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
+ t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
t++;
return min_t(unsigned long, t, MAX_PAUSE);
static inline void wb_dirty_limits(struct bdi_writeback *wb,
unsigned long dirty_thresh,
unsigned long background_thresh,
- unsigned long *bdi_dirty,
- unsigned long *bdi_thresh,
- unsigned long *bdi_bg_thresh)
+ unsigned long *wb_dirty,
+ unsigned long *wb_thresh,
+ unsigned long *wb_bg_thresh)
{
unsigned long wb_reclaimable;
/*
- * bdi_thresh is not treated as some limiting factor as
+ * wb_thresh is not treated as some limiting factor as
* dirty_thresh, due to reasons
- * - in JBOD setup, bdi_thresh can fluctuate a lot
+ * - in JBOD setup, wb_thresh can fluctuate a lot
* - in a system with HDD and USB key, the USB key may somehow
- * go into state (bdi_dirty >> bdi_thresh) either because
- * bdi_dirty starts high, or because bdi_thresh drops low.
+ * go into state (wb_dirty >> wb_thresh) either because
+ * wb_dirty starts high, or because wb_thresh drops low.
* In this case we don't want to hard throttle the USB key
- * dirtiers for 100 seconds until bdi_dirty drops under
- * bdi_thresh. Instead the auxiliary bdi control line in
+ * dirtiers for 100 seconds until wb_dirty drops under
+ * wb_thresh. Instead the auxiliary wb control line in
* wb_position_ratio() will let the dirtier task progress
- * at some rate <= (write_bw / 2) for bringing down bdi_dirty.
+ * at some rate <= (write_bw / 2) for bringing down wb_dirty.
*/
- *bdi_thresh = wb_dirty_limit(wb, dirty_thresh);
+ *wb_thresh = wb_dirty_limit(wb, dirty_thresh);
- if (bdi_bg_thresh)
- *bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh *
- background_thresh,
- dirty_thresh) : 0;
+ if (wb_bg_thresh)
+ *wb_bg_thresh = dirty_thresh ? div_u64((u64)*wb_thresh *
+ background_thresh,
+ dirty_thresh) : 0;
/*
* In order to avoid the stacked BDI deadlock we need
* actually dirty; with m+n sitting in the percpu
* deltas.
*/
- if (*bdi_thresh < 2 * wb_stat_error(wb)) {
+ if (*wb_thresh < 2 * wb_stat_error(wb)) {
wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE);
- *bdi_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK);
+ *wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK);
} else {
wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE);
- *bdi_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK);
+ *wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK);
}
}
for (;;) {
unsigned long now = jiffies;
- unsigned long uninitialized_var(bdi_thresh);
+ unsigned long uninitialized_var(wb_thresh);
unsigned long thresh;
- unsigned long uninitialized_var(bdi_dirty);
+ unsigned long uninitialized_var(wb_dirty);
unsigned long dirty;
unsigned long bg_thresh;
if (unlikely(strictlimit)) {
wb_dirty_limits(wb, dirty_thresh, background_thresh,
- &bdi_dirty, &bdi_thresh, &bg_thresh);
+ &wb_dirty, &wb_thresh, &bg_thresh);
- dirty = bdi_dirty;
- thresh = bdi_thresh;
+ dirty = wb_dirty;
+ thresh = wb_thresh;
} else {
dirty = nr_dirty;
thresh = dirty_thresh;
/*
* Throttle it only when the background writeback cannot
* catch-up. This avoids (excessively) small writeouts
- * when the bdi limits are ramping up in case of !strictlimit.
+ * when the wb limits are ramping up in case of !strictlimit.
*
- * In strictlimit case make decision based on the bdi counters
- * and limits. Small writeouts when the bdi limits are ramping
+ * In strictlimit case make decision based on the wb counters
+ * and limits. Small writeouts when the wb limits are ramping
* up are the price we consciously pay for strictlimit-ing.
*/
if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh)) {
if (!strictlimit)
wb_dirty_limits(wb, dirty_thresh, background_thresh,
- &bdi_dirty, &bdi_thresh, NULL);
+ &wb_dirty, &wb_thresh, NULL);
- dirty_exceeded = (bdi_dirty > bdi_thresh) &&
+ dirty_exceeded = (wb_dirty > wb_thresh) &&
((nr_dirty > dirty_thresh) || strictlimit);
if (dirty_exceeded && !wb->dirty_exceeded)
wb->dirty_exceeded = 1;
wb_update_bandwidth(wb, dirty_thresh, background_thresh,
- nr_dirty, bdi_thresh, bdi_dirty,
- start_time);
+ nr_dirty, wb_thresh, wb_dirty, start_time);
dirty_ratelimit = wb->dirty_ratelimit;
pos_ratio = wb_position_ratio(wb, dirty_thresh,
background_thresh, nr_dirty,
- bdi_thresh, bdi_dirty);
+ wb_thresh, wb_dirty);
task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
RATELIMIT_CALC_SHIFT;
- max_pause = wb_max_pause(wb, bdi_dirty);
+ max_pause = wb_max_pause(wb, wb_dirty);
min_pause = wb_min_pause(wb, max_pause,
task_ratelimit, dirty_ratelimit,
&nr_dirtied_pause);
dirty_thresh,
background_thresh,
nr_dirty,
- bdi_thresh,
- bdi_dirty,
+ wb_thresh,
+ wb_dirty,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,
dirty_thresh,
background_thresh,
nr_dirty,
- bdi_thresh,
- bdi_dirty,
+ wb_thresh,
+ wb_dirty,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,
/*
* In the case of an unresponding NFS server and the NFS dirty
- * pages exceeds dirty_thresh, give the other good bdi's a pipe
+ * pages exceeds dirty_thresh, give the other good wb's a pipe
* to go through, so that tasks on them still remain responsive.
*
* In theory 1 page is enough to keep the comsumer-producer
* pipe going: the flusher cleans 1 page => the task dirties 1
- * more page. However bdi_dirty has accounting errors. So use
+ * more page. However wb_dirty has accounting errors. So use
* the larger and more IO friendly wb_stat_error.
*/
- if (bdi_dirty <= wb_stat_error(wb))
+ if (wb_dirty <= wb_stat_error(wb))
break;
if (fatal_signal_pending(current))
projects / cascardo / linux.git / commitdiff