109 lines
4.5 KiB
Diff
109 lines
4.5 KiB
Diff
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From f8dc87ed130a0cfe1077242a4da2d621c4016bfb Mon Sep 17 00:00:00 2001
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From: Ken McDonell <kenj@kenj.id.au>
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Date: Thu, 4 Apr 2024 11:34:41 +1100
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Subject: [PATCH] libpcp: small derived metrics bug fix
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This is a partial fix for
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https://github.com/performancecopilot/pcp/issues/1921
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If the operand has the semantics of PM_SEM_COUNTER and the
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value goes backwards from one fetch to the next, then return
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no values for rate().
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There is QA to come, but this needs a final blessing from Oracle
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before the reproducer archive can be included.
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cherry-picked:- f8dc87ed130a0cfe1077242a4da2d621c4016bfb
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[Orabug: 36538820]
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Signed-off-by: sagar sagar <sagar.sagar@oracle.com>
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---
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man/man3/pmregisterderived.3 | 13 +++++++++----
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src/libpcp/src/derive_fetch.c | 23 ++++++++++++++++++++++-
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2 files changed, 31 insertions(+), 5 deletions(-)
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diff --git a/man/man3/pmregisterderived.3 b/man/man3/pmregisterderived.3
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index d8719f373..32963c3b3 100644
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--- a/man/man3/pmregisterderived.3
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+++ b/man/man3/pmregisterderived.3
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@@ -485,15 +485,20 @@ metric x with the dimension in the
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.B time
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domain decreased by one and scaling if required in the time utilization case
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where the operand is in units of time, and the derived metric is unitless.
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-This mimics the rate conversion applied to counter metrics by tools
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+There is one value in the result
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+for each instance that appears in both the current and the previous
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+sample, except in the case where the metric x has
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+the semantics of a counter, i.e. PM_SEM_COUNTER, and
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+current value of an instance is smaller than the previous value
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+of the same instance then no value is
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+returned for this instance (this corresponds to a ``counter wrap'' or a ``counter reset'').
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+These rules
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+mimic the rate conversion applied to counter metrics by tools
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such as
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.BR pmval (1),
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.BR pmie (1)
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and
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.BR pmchart (1).
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-There is one value in the result
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-for each instance that appears in both the current and the previous
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-sample.
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T}
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_
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instant(x) T{
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diff --git a/src/libpcp/src/derive_fetch.c b/src/libpcp/src/derive_fetch.c
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index 62921ece4..ed5f6ebcf 100644
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--- a/src/libpcp/src/derive_fetch.c
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+++ b/src/libpcp/src/derive_fetch.c
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@@ -847,7 +847,13 @@ eval_expr(__pmContext *ctxp, node_t *np, struct timespec *stamp, int numpmid,
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}
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}
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else {
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- /* rate() conversion, type will be DOUBLE */
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+ /*
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+ * rate() conversion, type will be DOUBLE
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+ *
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+ * For COUNTER metrics, return "no value" if the counter is
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+ * NOT monotonic increasing ... this matches what pmval(1)
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+ * and pmie(1) do in the same circumstances.
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+ */
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struct timespec stampdiff;
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stampdiff = np->data.info->stamp;
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@@ -857,18 +863,33 @@ eval_expr(__pmContext *ctxp, node_t *np, struct timespec *stamp, int numpmid,
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np->data.info->ivlist[k].value.d = (double)(np->left->data.info->ivlist[i].value.l - np->left->data.info->last_ivlist[j].value.l);
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break;
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case PM_TYPE_U32:
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+ if (np->left->desc.sem == PM_SEM_COUNTER &&
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+ np->left->data.info->ivlist[i].value.ul < np->left->data.info->last_ivlist[j].value.ul)
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+ continue;
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np->data.info->ivlist[k].value.d = (double)(np->left->data.info->ivlist[i].value.ul - np->left->data.info->last_ivlist[j].value.ul);
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break;
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case PM_TYPE_64:
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+ if (np->left->desc.sem == PM_SEM_COUNTER &&
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+ np->left->data.info->ivlist[i].value.ll < np->left->data.info->last_ivlist[j].value.ll)
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+ continue;
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np->data.info->ivlist[k].value.d = (double)(np->left->data.info->ivlist[i].value.ll - np->left->data.info->last_ivlist[j].value.ll);
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break;
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case PM_TYPE_U64:
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+ if (np->left->desc.sem == PM_SEM_COUNTER &&
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+ np->left->data.info->ivlist[i].value.ull < np->left->data.info->last_ivlist[j].value.ull)
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+ continue;
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np->data.info->ivlist[k].value.d = (double)(np->left->data.info->ivlist[i].value.ull - np->left->data.info->last_ivlist[j].value.ull);
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break;
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case PM_TYPE_FLOAT:
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+ if (np->left->desc.sem == PM_SEM_COUNTER &&
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+ np->left->data.info->ivlist[i].value.f < np->left->data.info->last_ivlist[j].value.f)
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+ continue;
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np->data.info->ivlist[k].value.d = (double)(np->left->data.info->ivlist[i].value.f - np->left->data.info->last_ivlist[j].value.f);
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break;
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case PM_TYPE_DOUBLE:
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+ if (np->left->desc.sem == PM_SEM_COUNTER &&
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+ np->left->data.info->ivlist[i].value.d < np->left->data.info->last_ivlist[j].value.d)
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+ continue;
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np->data.info->ivlist[k].value.d = np->left->data.info->ivlist[i].value.d - np->left->data.info->last_ivlist[j].value.d;
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break;
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default:
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--
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2.39.3
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