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commit c226e98096c7bdb6296a96257439724e1f68217e
Author: Nathan Scott <nathans@redhat.com>
Date: Tue Apr 26 12:00:32 2022 +1000
libpcp: optimize indom handling in fetchgroup code
Looking into some pcp-ss issues I immediately encountered a
noticable elapsed time difference between executing just ss
versus pcp-ss. It turned out it was due to fetchgroup code
not really understanding how the underlying indom APIs work
and repeatedly refreshing shared indoms (all metrics in the
pcp-ss tool actually share one indom) once for every metric
that happens to use that indom - i.e. many times per fetch.
These changes resulted in a 5x speedup in pcp-ss and it now
completes instantly as expected. Additionally, we use alot
less memory now for the many-metrics-sharing-an-indom case.
diff -Naurp pcp-5.3.7.patched/src/libpcp/src/fetchgroup.c pcp-5.3.7/src/libpcp/src/fetchgroup.c
--- pcp-5.3.7.patched/src/libpcp/src/fetchgroup.c 2022-04-05 09:05:43.000000000 +1000
+++ pcp-5.3.7/src/libpcp/src/fetchgroup.c 2023-03-08 18:46:43.486916630 +1100
@@ -34,6 +34,19 @@
/* ------------------------------------------------------------------------ */
/*
+ * Cache to avoid unnecessary repeated calls to pmGetInDom for individual
+ * instance domains. This involves a round trip to pmcd and it does not
+ * change frequently (certainly not for processing results of one sample).
+ */
+struct __pmInDomCache {
+ pmInDom indom;
+ int *codes; /* saved from pmGetInDom */
+ char **names;
+ unsigned int size;
+ int refreshed;
+};
+
+/*
* An individual fetch-group is a linked list of requests tied to a
* particular pcp context (which the fetchgroup owns). NB: This is
* opaque to the PMAPI client.
@@ -43,8 +56,10 @@ struct __pmFetchGroup {
int wrap; /* wrap-handling flag, set at fg-create-time */
pmResult *prevResult;
struct __pmFetchGroupItem *items;
+ struct __pmInDomCache *unique_indoms;
pmID *unique_pmids;
size_t num_unique_pmids;
+ size_t num_unique_indoms;
};
/*
@@ -81,9 +96,6 @@ struct __pmFetchGroupItem {
struct {
pmID metric_pmid;
pmDesc metric_desc;
- int *indom_codes; /* saved from pmGetInDom */
- char **indom_names;
- unsigned indom_size;
struct __pmFetchGroupConversionSpec conv;
int *output_inst_codes; /* NB: may be NULL */
char **output_inst_names; /* NB: may be NULL */
@@ -168,9 +180,7 @@ pmfg_add_pmid(pmFG pmfg, pmID pmid)
/*
* Populate given pmFGI item structure based on common lookup &
* verification for pmfg inputs. Adjust instance profile to
- * include requested instance. If it's a derived metric, we
- * don't know what instance domain(s) it could involve, so we
- * clear the instance profile entirely.
+ * include requested instance.
*/
static int
pmfg_lookup_item(const char *metric, const char *instance, pmFGI item)
@@ -206,9 +216,12 @@ pmfg_lookup_item(const char *metric, con
/* Same for a whole indom. Add the whole instance profile. */
static int
-pmfg_lookup_indom(const char *metric, pmFGI item)
+pmfg_lookup_indom(pmFG pmfg, const char *metric, pmFGI item)
{
- int sts;
+ struct __pmInDomCache *indoms;
+ pmInDom indom;
+ size_t size;
+ int i, sts;
assert(item != NULL);
assert(item->type == pmfg_indom);
@@ -221,14 +234,34 @@ pmfg_lookup_indom(const char *metric, pm
return sts;
/* As a convenience to users, we also accept non-indom'd metrics */
- if (item->u.indom.metric_desc.indom == PM_INDOM_NULL)
+ if ((indom = item->u.indom.metric_desc.indom) == PM_INDOM_NULL)
return 0;
/*
+ * Insert into the instance domain cache if not seen previously
+ */
+ for (i = 0; i < pmfg->num_unique_indoms; i++) {
+ if (pmfg->unique_indoms[i].indom == indom)
+ return 0;
+ }
+
+ size = sizeof(struct __pmInDomCache) * (pmfg->num_unique_indoms + 1);
+ indoms = realloc(pmfg->unique_indoms, size);
+
+ if (indoms == NULL)
+ return -ENOMEM;
+ pmfg->unique_indoms = indoms;
+ pmfg->unique_indoms[pmfg->num_unique_indoms].indom = indom;
+ pmfg->unique_indoms[pmfg->num_unique_indoms].codes = NULL;
+ pmfg->unique_indoms[pmfg->num_unique_indoms].names = NULL;
+ pmfg->unique_indoms[pmfg->num_unique_indoms].refreshed = 0;
+ pmfg->num_unique_indoms++;
+
+ /*
* Add all instances; this will override any other past or future
* piecemeal instance requests from __pmExtendFetchGroup_lookup.
*/
- return pmAddProfile(item->u.indom.metric_desc.indom, 0, NULL);
+ return pmAddProfile(indom, 0, NULL);
}
/* Same for an event field. */
@@ -581,7 +614,7 @@ pmfg_reinit_indom(pmFGI item)
if (item->u.indom.output_inst_names)
for (i = 0; i < item->u.indom.output_maxnum; i++)
- item->u.indom.output_inst_names[i] = NULL; /* break ref into indom_names[] */
+ item->u.indom.output_inst_names[i] = NULL; /* ptr into names[] */
if (item->u.indom.output_stss)
for (i = 0; i < item->u.indom.output_maxnum; i++)
@@ -857,11 +890,11 @@ pmfg_fetch_timestamp(pmFG pmfg, pmFGI it
static void
pmfg_fetch_indom(pmFG pmfg, pmFGI item, pmResult *newResult)
{
- int sts = 0;
- int i;
- unsigned j;
- int need_indom_refresh;
+ int i, sts = 0;
+ unsigned int j, k;
+ struct __pmInDomCache *cache;
const pmValueSet *iv;
+ pmInDom indom;
assert(item != NULL);
assert(item->type == pmfg_indom);
@@ -901,36 +934,43 @@ pmfg_fetch_indom(pmFG pmfg, pmFGI item,
/*
* Analyze newResult to see whether it only contains instances we
- * already know. This is unfortunately an O(N**2) operation. It
- * could be made a bit faster if we build a pmGetInDom()- variant
- * that provides instances in sorted order.
+ * already know.
*/
- need_indom_refresh = 0;
- if (item->u.indom.output_inst_names) { /* Caller interested at all? */
- for (j = 0; j < (unsigned)iv->numval; j++) {
- unsigned k;
- for (k = 0; k < item->u.indom.indom_size; k++)
- if (item->u.indom.indom_codes[k] == iv->vlist[j].inst)
+ cache = NULL;
+ indom = item->u.indom.metric_desc.indom;
+ for (j = 0; j < pmfg->num_unique_indoms; j++) {
+ if (indom != pmfg->unique_indoms[j].indom)
+ continue;
+ cache = &pmfg->unique_indoms[j];
+ break;
+ }
+ if (cache && cache->refreshed &&
+ item->u.indom.output_inst_names) { /* Caller interested at all? */
+ for (j = 0; j < (unsigned int)iv->numval; j++) {
+ for (k = 0; k < cache->size; k++)
+ if (cache->codes[k] == iv->vlist[j].inst)
break;
- if (k >= item->u.indom.indom_size) {
- need_indom_refresh = 1;
+ if (k >= cache->size) {
+ cache->refreshed = 0;
break;
}
}
}
- if (need_indom_refresh) {
- free(item->u.indom.indom_codes);
- free(item->u.indom.indom_names);
- sts = pmGetInDom(item->u.indom.metric_desc.indom,
- &item->u.indom.indom_codes, &item->u.indom.indom_names);
+ if (cache && !cache->refreshed) {
+ cache->refreshed = 1;
+ free(cache->codes);
+ free(cache->names);
+ sts = pmGetInDom(indom, &cache->codes, &cache->names);
if (sts < 1) {
/* Need to manually clear; pmGetInDom claims they are undefined. */
- item->u.indom.indom_codes = NULL;
- item->u.indom.indom_names = NULL;
- item->u.indom.indom_size = 0;
+ cache->codes = NULL;
+ cache->names = NULL;
+ cache->size = 0;
}
else {
- item->u.indom.indom_size = sts;
+ if (sts < 0)
+ cache->refreshed = 0;
+ cache->size = sts;
}
/*
* NB: Even if the pmGetInDom failed, we can proceed with
@@ -965,18 +1005,19 @@ pmfg_fetch_indom(pmFG pmfg, pmFGI item,
* results from pmGetIndom.
*/
if (item->u.indom.output_inst_names) {
- unsigned k;
-
- for (k = 0; k < item->u.indom.indom_size; k++) {
- if (item->u.indom.indom_codes[k] == jv->inst) {
- /*
- * NB: copy the indom name char* by value.
- * The user is not supposed to modify / free this pointer,
- * or use it after a subsequent fetch or delete operation.
- */
- item->u.indom.output_inst_names[j] =
- item->u.indom.indom_names[k];
- break;
+ if (cache == NULL)
+ item->u.indom.output_inst_names[j] = NULL;
+ else {
+ for (k = 0; k < cache->size; k++) {
+ if (cache->codes[k] == jv->inst) {
+ /*
+ * NB: copy the indom name char* by value.
+ * User may not modify / free this pointer,
+ * nor use it after subsequent fetch / delete.
+ */
+ item->u.indom.output_inst_names[j] = cache->names[k];
+ break;
+ }
}
}
}
@@ -1201,8 +1242,7 @@ out:
static int
pmfg_clear_profile(pmFG pmfg)
{
- int sts;
- pmFGI item;
+ int i, sts;
sts = pmUseContext(pmfg->ctx);
if (sts != 0)
@@ -1216,10 +1256,9 @@ pmfg_clear_profile(pmFG pmfg)
* Any errors here are benign (or rather there's nothing we can do
* about 'em), so ignore pmDelProfile() return value.
*/
- for (item = pmfg->items; item; item = item->next) {
- if (item->u.item.metric_desc.indom != PM_INDOM_NULL)
- (void)pmDelProfile(item->u.item.metric_desc.indom, 0, NULL);
- }
+ for (i = 0; i < pmfg->num_unique_indoms; i++)
+ (void)pmDelProfile(pmfg->unique_indoms[i].indom, 0, NULL);
+
return 0;
}
@@ -1434,7 +1473,7 @@ pmExtendFetchGroup_indom(pmFG pmfg,
item->type = pmfg_indom;
- sts = pmfg_lookup_indom(metric, item);
+ sts = pmfg_lookup_indom(pmfg, metric, item);
if (sts != 0)
goto out;
@@ -1615,7 +1654,6 @@ pmFetchGroup(pmFG pmfg)
if (pmfg == NULL)
return -EINVAL;
-
/*
* Walk the fetchgroup, reinitializing every output spot, regardless of
* later errors.
@@ -1705,6 +1743,7 @@ int
pmClearFetchGroup(pmFG pmfg)
{
pmFGI item;
+ size_t n;
if (pmfg == NULL)
return -EINVAL;
@@ -1719,8 +1758,6 @@ pmClearFetchGroup(pmFG pmfg)
break;
case pmfg_indom:
pmfg_reinit_indom(item);
- free(item->u.indom.indom_codes);
- free(item->u.indom.indom_names);
break;
case pmfg_event:
pmfg_reinit_event(item);
@@ -1739,11 +1776,21 @@ pmClearFetchGroup(pmFG pmfg)
if (pmfg->prevResult)
pmFreeResult(pmfg->prevResult);
pmfg->prevResult = NULL;
+
if (pmfg->unique_pmids)
free(pmfg->unique_pmids);
pmfg->unique_pmids = NULL;
pmfg->num_unique_pmids = 0;
+ for (n = 0; n < pmfg->num_unique_indoms; n++) {
+ free(pmfg->unique_indoms[n].codes);
+ free(pmfg->unique_indoms[n].names);
+ }
+ if (pmfg->unique_indoms)
+ free(pmfg->unique_indoms);
+ pmfg->unique_indoms = NULL;
+ pmfg->num_unique_indoms = 0;
+
return pmfg_clear_profile(pmfg);
}
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