stan/jdk-24
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

8290868: NMT: MallocSiteTable statistics improvements

Browse Source 
Reviewed-by: zgu, lucy
This commit is contained in:
Thomas Stuefe 2022-07-30 13:03:25 +00:00
parent 357902415d
commit 32d410a1af
1 changed files with 18 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
src/hotspot/share/services/mallocSiteTable.cpp
View File

@ -189,6 +189,10 @@ bool MallocSiteTable::walk_malloc_site(MallocSiteWalker* walker) {
return walk(walker);
}
static int qsort_helper(const void* a, const void* b) {
return *((uint16_t*)a) - *((uint16_t*)b);
}
void MallocSiteTable::print_tuning_statistics(outputStream* st) {
// Total number of allocation sites, include empty sites
int total_entries = 0;
@ -197,11 +201,16 @@ void MallocSiteTable::print_tuning_statistics(outputStream* st) {
// Number of captured call stack distribution
int stack_depth_distribution[NMT_TrackingStackDepth + 1] = { 0 };
// Chain lengths
int lengths[table_size] = { 0 };
uint16_t lengths[table_size] = { 0 };
// Unused buckets
int unused_buckets = 0;
for (int i = 0; i < table_size; i ++) {
int this_chain_length = 0;
const MallocSiteHashtableEntry* head = _table[i];
if (head == NULL) {
unused_buckets ++;
}
while (head != NULL) {
total_entries ++;
this_chain_length ++;
@ -214,43 +223,21 @@ void MallocSiteTable::print_tuning_statistics(outputStream* st) {
stack_depth_distribution[callstack_depth] ++;
head = head->next();
}
lengths[i] = this_chain_length;
lengths[i] = (uint16_t)MIN2(this_chain_length, USHRT_MAX);
}
st->print_cr("Malloc allocation site table:");
st->print_cr("\tTotal entries: %d", total_entries);
st->print_cr("\tEmpty entries: %d (%2.2f%%)", empty_entries, ((float)empty_entries * 100) / total_entries);
st->print_cr("\tEmpty entries (no outstanding mallocs): %d (%2.2f%%)",
empty_entries, ((float)empty_entries * 100) / total_entries);
st->cr();
// We report the hash distribution (chain length distribution) of the n shortest chains
// - under the assumption that this usually contains all lengths. Reporting threshold
// is 20, and the expected avg chain length is 5..6 (see table size).
static const int chain_length_threshold = 20;
int chain_length_distribution[chain_length_threshold] = { 0 };
int over_threshold = 0;
int longest_chain_length = 0;
for (int i = 0; i < table_size; i ++) {
if (lengths[i] >= chain_length_threshold) {
over_threshold ++;
} else {
chain_length_distribution[lengths[i]] ++;
}
longest_chain_length = MAX2(longest_chain_length, lengths[i]);
}
qsort(lengths, table_size, sizeof(uint16_t), qsort_helper);
st->print_cr("Hash distribution:");
if (chain_length_distribution[0] == 0) {
st->print_cr("no empty buckets.");
} else {
st->print_cr("%d buckets are empty.", chain_length_distribution[0]);
}
for (int len = 1; len < MIN2(longest_chain_length + 1, chain_length_threshold); len ++) {
st->print_cr("%2d %s: %d.", len, (len == 1 ? " entry" : "entries"), chain_length_distribution[len]);
}
if (longest_chain_length >= chain_length_threshold) {
st->print_cr(">=%2d entries: %d.", chain_length_threshold, over_threshold);
}
st->print_cr("most entries: %d.", longest_chain_length);
st->print_cr("Bucket chain length distribution:");
st->print_cr("unused: %d", unused_buckets);
st->print_cr("longest: %d", lengths[table_size - 1]);
st->print_cr("median: %d", lengths[table_size / 2]);
st->cr();
st->print_cr("Call stack depth distribution:");