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move c1-c2 backpresure to linear backpressure model; removes a few hundred lines of fussy code, and should enable further simplifiactions

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git-svn-id: svn+ssh://svn.corp.yahoo.com/yahoo/yrl/labs/pnuts/code/logstore@1488 8dad8b1f-cf64-0410-95b6-bcf113ffbcfe
This commit is contained in:
sears 2010-12-13 21:17:35 +00:00
parent 347a4126f3
commit 7e44641799
2 changed files with 42 additions and 157 deletions
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157
mergeManager.cpp
View file

@ -48,31 +48,6 @@ void mergeManager::new_merge(int mergeLevel) {
void mergeManager::set_c0_size(int64_t size) {
c0->target_size = size;
}
void mergeManager::sleep_on_mini_delta(mergeStats *s, int delta) {
s->mini_delta += delta;
if(/*s->merge_level < 2*/ s->merge_level == 1 && s->mergeable_size && delta) {
int64_t effective_max_delta = (int64_t)(UPDATE_PROGRESS_PERIOD * s->bps);
// if(s->merge_level == 0) { s->base_size = ltable->tree_bytes; }
if(s->mini_delta > effective_max_delta) {
struct timeval now;
gettimeofday(&now, 0);
double now_double = tv_to_double(&now);
double elapsed_delta = now_double - ts_to_double(&s->last_mini_tick);
double slp = UPDATE_PROGRESS_PERIOD - elapsed_delta;
if(slp > 0.001) {
struct timespec sleeptime;
double_to_ts(&sleeptime, slp);
nanosleep(&sleeptime, 0);
printf("%d Sleep A %f\n", s->merge_level, slp);
}
double_to_ts(&s->last_mini_tick, now_double);
s->mini_delta = 0;
}
}
}
void mergeManager::update_progress(mergeStats * s, int delta) {
s->delta += delta;
@ -125,111 +100,6 @@ void mergeManager::update_progress(mergeStats * s, int delta) {
}
}
void mergeManager::tick_based_on_merge_progress(mergeStats *s) {
/* model the effect of linux + stasis' write caches; at the end
of this merge, we need to force up to FORCE_INTERVAL bytes
after we think we're done writing the next component. */
int64_t overshoot_fudge = (int64_t)((s->out_progress) * ((double)FORCE_INTERVAL));
/* model the effect of amortizing this computation: we could
become this much more overshot if we don't act now. */
int64_t overshoot_fudge2 = UPDATE_PROGRESS_DELTA;
/* multiply by 2 for good measure. These are 'soft' walls, and
still let writes trickle through. Once we've exhausted the
fudge factors, we'll hit a hard wall, and stop writes
entirely, so it's better to start throttling too early than
too late. */
overshoot_fudge *= 2;
overshoot_fudge2 *= 4;
if(overshoot_fudge > 0.01 * s->target_size) { overshoot_fudge = (int64_t)(0.01 * (double)s->target_size); }
if(overshoot_fudge2 > 0.01 * s->target_size) { overshoot_fudge2 = (int64_t)(0.01 * (double)s->target_size); }
const double max_c0_sleep = 0.1;
const double min_c0_sleep = 0.01;
const double max_c1_sleep = 0.5;
const double min_c1_sleep = 0.1;
double max_sleep = s->merge_level == 0 ? max_c0_sleep : max_c1_sleep;
double min_sleep = s->merge_level == 0 ? min_c0_sleep : min_c1_sleep;
int spin = 0;
double total_sleep = 0.0;
while(1) {
int64_t overshoot = 0;
int64_t overshoot2 = 0;
int64_t raw_overshoot = 0;
double bps;
// This needs to be here (and not in update_progress), since the other guy's in_progress changes while we sleep.
mergeStats * s1;
if(s->merge_level == 0) {
// dead code
s1 = c1;
} else {
s1 = c2;
}
if(s->mergeable_size) { // only apply backpressure if the next merger is not waiting for us
rwlc_readlock(ltable->header_mut);
if(s1->active && s->mergeable_size) {
raw_overshoot = (int64_t)(((double)s->target_size) * (s->out_progress - s1->in_progress));
overshoot = raw_overshoot + overshoot_fudge;
overshoot2 = raw_overshoot + overshoot_fudge2;
bps = s1->bps;
}
rwlc_unlock(ltable->header_mut);
}
if(s->merge_level == 1) {
if(s1->active && s->mergeable_size) {
cur_c1_c2_progress_delta = s1->in_progress - s->out_progress;
} else if(!s->mergeable_size) {
cur_c1_c2_progress_delta = 1;
} else {
// s1 is not active.
cur_c1_c2_progress_delta = 0;
}
}
//#define PP_THREAD_INFO
#ifdef PP_THREAD_INFO
printf("\nMerge thread %d %6f %6f Overshoot: raw=%lld, d=%lld eff=%lld Throttle min(1, %6f) spin %d, total_sleep %6.3f\n", s->merge_level, c0_out_progress, c0_c1_in_progress, raw_overshoot, overshoot_fudge, overshoot, -1.0, spin, total_sleep);
#endif
bool one_threshold = (overshoot > 0 || overshoot2 > 0) || (raw_overshoot > 0);
bool two_threshold = (overshoot > 0 || overshoot2 > 0) && (raw_overshoot > 0);
if(one_threshold && (two_threshold || total_sleep < 0.01)) {
// throttle
// it took "elapsed" seconds to process "tick_length_bytes" mb
double sleeptime = 2.0 * fmax((double)overshoot,(double)overshoot2) / bps;
if(sleeptime < min_sleep) { sleeptime = min_sleep; }
if(sleeptime > max_sleep) { sleeptime = max_sleep; }
spin ++;
total_sleep += sleeptime;
if((spin > 40) || (total_sleep > (max_sleep * 20.0))) {
printf("\nMerge thread %d c0->out=%f c1->in=%f c1->out=%f c2->in=%f\n", s->merge_level, c0->out_progress, c1->in_progress, c1->out_progress, c2->in_progress);
printf("\nMerge thread %d Overshoot: raw=%lld, d=%lld eff=%lld eff2=%lld Throttle min(1, %6f) spin %d, total_sleep %6.3f\n", s->merge_level, (long long)raw_overshoot, (long long)overshoot_fudge, (long long)overshoot, (long long)overshoot2, sleeptime, spin, total_sleep);
}
sleeping[s->merge_level] = true;
struct timespec ts;
double_to_ts(&ts, sleeptime);
nanosleep(&ts, 0);
// printf("%d Sleep B %f\n", s->merge_level, sleeptime);
sleeping[s->merge_level] = false;
update_progress(s1, 0);
} else if(overshoot > 0 || overshoot2 > 0) { // this is our second time around the loop, so remember we're in the hole
s->need_tick ++;
if(s->need_tick > 500) { printf("need tick %d\n", s->need_tick); }
} else { // all is well in the world. we can run worry-free for a while.
s->need_tick = 0;
}
break;
}
}
/**
* This function is invoked periodically by the merge threads. It updates mergeManager's statistics, and applies
* backpressure as necessary.
@ -252,9 +122,27 @@ void mergeManager::tick_based_on_merge_progress(mergeStats *s) {
* bytes_consumed_by_merger = sum(bytes_in_small_delta)
*/
void mergeManager::tick(mergeStats * s) {
if(s->need_tick) {
if(s->merge_level == 1) { // apply backpressure based on merge progress.
tick_based_on_merge_progress(s);
if(s->need_tick) {
s->need_tick = 0;
// Only apply back pressure if next thread is not waiting on us.
rwlc_readlock(ltable->header_mut);
if(c1->mergeable_size && c2->active) {
double delta = c1->out_progress - c2->in_progress;
rwlc_unlock(ltable->header_mut);
if(delta > -0.01) {
delta += 0.01; // delta > 0;
double slp = 0.001 + delta;
struct timespec sleeptime;
DEBUG("\ndisk sleeping %0.6f tree_megabytes %0.3f\n", slp, ((double)ltable->tree_bytes)/(1024.0*1024.0));
double_to_ts(&sleeptime,slp);
nanosleep(&sleeptime, 0);
s->need_tick = 1;
}
} else {
rwlc_unlock(ltable->header_mut);
}
}
} else if(s->merge_level == 0) {
// Simple backpressure algorithm based on how full C0 is.
@ -271,16 +159,15 @@ void mergeManager::tick(mergeStats * s) {
double delta = ((double)ltable->tree_bytes)/(0.9*(double)ltable->max_c0_size); // 0 <= delta <= 1.111...
delta -= 1.0;
if(delta > 0.00005) {
double slp = 0.001 + 10.0 * delta; //0.0015 < slp < 1.112111..
double slp = 0.001 + 5.0 * delta; //0.0015 < slp < 1.112111..
DEBUG("\nsleeping %0.6f tree_megabytes %0.3f\n", slp, ((double)ltable->tree_bytes)/(1024.0*1024.0));
DEBUG("\nmem sleeping %0.6f tree_megabytes %0.3f\n", slp, ((double)ltable->tree_bytes)/(1024.0*1024.0));
struct timespec sleeptime;
double_to_ts(&sleeptime, slp);
DEBUG("%d Sleep C %f\n", s->merge_level, slp);
nanosleep(&sleeptime, 0);
}
}
}
}
void mergeManager::read_tuple_from_small_component(int merge_level, datatuple * tup) {

2
mergeManager.h
View file

@ -43,10 +43,8 @@ public:
void new_merge(int mergelevel);
void set_c0_size(int64_t size);
void sleep_on_mini_delta(mergeStats *s, int delta);
void update_progress(mergeStats *s, int delta);
void tick(mergeStats * s);
void tick_based_on_merge_progress(mergeStats * s);
mergeStats* get_merge_stats(int mergeLevel);
void read_tuple_from_small_component(int merge_level, datatuple * tup);
void read_tuple_from_large_component(int merge_level, datatuple * tup) {