Author: Tobias Weber <[email protected]>
Branch: c8-tcp-style-trx-length
Changeset: r2134:70e630a22710
Date: 2017-07-21 14:42 +0200
http://bitbucket.org/pypy/stmgc/changeset/70e630a22710/
Log: Decrease trx len just ten percent at a time below min
diff --git a/c8/stm/nursery.c b/c8/stm/nursery.c
--- a/c8/stm/nursery.c
+++ b/c8/stm/nursery.c
@@ -23,15 +23,19 @@
// corresponds to ~4 KB nursery fill
#define STM_MIN_RELATIVE_TRANSACTION_LENGTH (0.000001)
-#define BACKOFF_COUNT (10)
+#define BACKOFF_COUNT (5)
#define BACKOFF_MULTIPLIER (BACKOFF_COUNT /
-log10(STM_MIN_RELATIVE_TRANSACTION_LENGTH))
static inline void set_backoff(stm_thread_local_t *tl, double rel_trx_len) {
- // the shorter the trx, the more backoff: 100 at min trx length,
proportional decrease to 5 at max trx length (think a/x + b = backoff)
+ /* the shorter the trx, the more backoff:
+ think a*x + b = backoff, x := -log(rel-trx-len),
+ backoff is <BACKOFF_COUNT> + b at default trx length,
+ linear decrease to b at max trx length */
+ const int b = 5;
tl->transaction_length_backoff =
- (int)((BACKOFF_MULTIPLIER * -log10(rel_trx_len)) + 5);
+ (int)((BACKOFF_MULTIPLIER * -log10(rel_trx_len)) + b);
// printf("thread %d, backoff %d\n", tl->thread_local_counter,
tl->transaction_length_backoff);
- tl->linear_transaction_length_increment = rel_trx_len / BACKOFF_COUNT;
+ tl->linear_transaction_length_increment = rel_trx_len / (BACKOFF_COUNT +
b);
}
static inline double get_new_transaction_length(stm_thread_local_t *tl, bool
aborts) {
@@ -41,7 +45,8 @@
if (aborts) {
new = previous / multiplier;
if (new < STM_MIN_RELATIVE_TRANSACTION_LENGTH) {
- new = STM_MIN_RELATIVE_TRANSACTION_LENGTH;
+ // reached min trx length, only decrease slowly
+ new = 0.9 * previous;
}
set_backoff(tl, new);
} else if (tl->transaction_length_backoff == 0) {
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