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ui: implement pivot for flamegraph
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This CL implements pivot support in the Perfetto UI bringing us to
full parity with the flamegraph tab of internal pprof for single
profiles.

Change-Id: I03e9b868ce6e99bf884b62a3d39ccaf9f0aaad94
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@LalitMaganti
LalitMaganti committed Jul 22, 2024
1 parent 1beb087 commit e127b95
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Showing 3 changed files with 240 additions and 64 deletions.
123 changes: 105 additions & 18 deletions src/trace_processor/perfetto_sql/stdlib/viz/flamegraph.sql
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,12 +15,15 @@

include perfetto module graphs.scan;

-- For each frame in |tab|, returns a row containing the result of running
-- all the filtering operations over that frame's name.
CREATE PERFETTO MACRO _viz_flamegraph_prepare_filter(
tab TableOrSubquery,
show_stack Expr,
hide_stack Expr,
show_from_frame Expr,
hide_frame Expr,
pivot Expr,
impossible_stack_bits Expr
)
RETURNS TableOrSubquery
Expand All @@ -29,11 +32,16 @@ AS (
*,
IIF($hide_stack, $impossible_stack_bits, $show_stack) AS stackBits,
$show_from_frame As showFromFrameBits,
$hide_frame = 0 AS showFrame
$hide_frame = 0 AS showFrame,
$pivot AS isPivot
FROM $tab
ORDER BY id
);

-- Walks the forest from root to leaf and performs the following operations:
-- 1) removes frames which were filtered out
-- 2) make any pivot nodes become the roots
-- 3) computes whether the stack as a whole should be retained or not
CREATE PERFETTO MACRO _viz_flamegraph_filter_frames(
source TableOrSubquery,
show_from_frame_bits Expr
Expand All @@ -54,6 +62,7 @@ AS (
NULL
) AS filteredId,
NULL AS filteredParentId,
NULL AS filteredUnpivotedParentId,
IIF(
showFrame,
showFromFrameBits,
Expand All @@ -70,12 +79,13 @@ AS (
SELECT
g.filteredId AS id,
g.filteredParentId AS parentId,
g.filteredUnpivotedParentId AS unpivotedParentId,
g.stackBits,
SUM(t.value) AS value
FROM _graph_scan!(
edges,
inits,
(filteredId, filteredParentId, showFromFrameBits, stackBits),
(filteredId, filteredParentId, filteredUnpivotedParentId, showFromFrameBits, stackBits),
(
SELECT
t.id,
Expand All @@ -86,9 +96,14 @@ AS (
) AS filteredId,
IIF(
x.showFrame AND (t.showFromFrameBits | x.showFromFrameBits) = $show_from_frame_bits,
t.filteredId,
IIF(x.isPivot, NULL, t.filteredId),
t.filteredParentId
) AS filteredParentId,
IIF(
x.showFrame AND (t.showFromFrameBits | x.showFromFrameBits) = $show_from_frame_bits,
t.filteredId,
t.filteredParentId
) AS filteredUnpivotedParentId,
IIF(
x.showFrame,
(t.showFromFrameBits | x.showFromFrameBits),
Expand All @@ -109,6 +124,10 @@ AS (
ORDER BY filteredId
);

-- Walks the forest from leaves to root and does the following:
-- 1) removes nodes whose stacks are filtered out
-- 2) computes the cumulative value for each node (i.e. the sum of the self
-- value of the node and all descendants).
CREATE PERFETTO MACRO _viz_flamegraph_accumulate(
filtered TableOrSubquery,
showStackBits Expr
Expand Down Expand Up @@ -149,34 +168,96 @@ AS (
ORDER BY id
);

CREATE PERFETTO MACRO _viz_flamegraph_hash(
-- Propogates the cumulative value of the pivot nodes to the roots
-- and computes the "fingerprint" of the path.
CREATE PERFETTO MACRO _viz_flamegraph_upwards_hash(
source TableOrSubquery,
filtered TableOrSubquery,
accumulated TableOrSubquery,
show_from_frame_bits Expr
accumulated TableOrSubquery
)
RETURNS TableOrSubquery
AS (
WITH edges AS (
SELECT id AS source_node_id, unpivotedParentId AS dest_node_id
FROM $filtered
WHERE unpivotedParentId IS NOT NULL
),
inits AS (
SELECT
f.id,
HASH(-1, s.name) AS hash,
NULL AS parentHash,
-1 AS depth,
a.cumulativeValue
FROM $filtered f
JOIN $source s USING (id)
JOIN $accumulated a USING (id)
WHERE f.parentId IS NULL
AND f.unpivotedParentId IS NOT NULL
AND a.cumulativeValue > 0
)
SELECT
g.id,
g.hash,
g.parentHash,
g.depth,
s.name,
f.value,
a.cumulativeValue
g.cumulativeValue
FROM _graph_scan!(
edges,
inits,
(hash, parentHash, depth, cumulativeValue),
(
SELECT parentId AS source_node_id, id AS dest_node_id
FROM $filtered
WHERE parentId IS NOT NULL
),
(
SELECT f.id, HASH(s.name) AS hash, NULL AS parentHash, 0 AS depth
FROM $filtered f
JOIN $source s USING (id)
WHERE f.parentId IS NULL
),
SELECT
t.id,
HASH(t.hash, x.name) AS hash,
t.hash AS parentHash,
t.depth - 1 AS depth,
t.cumulativeValue
FROM $table t
JOIN $source x USING (id)
)
) g
JOIN $source s USING (id)
JOIN $filtered f USING (id)
);

-- Computes the "fingerprint" of the path by walking from the laves
-- to the root.
CREATE PERFETTO MACRO _viz_flamegraph_downwards_hash(
source TableOrSubquery,
filtered TableOrSubquery,
accumulated TableOrSubquery
)
RETURNS TableOrSubquery
AS (
WITH edges AS (
SELECT parentId AS source_node_id, id AS dest_node_id
FROM $filtered
WHERE parentId IS NOT NULL
),
inits AS (
SELECT
f.id,
HASH(1, s.name) AS hash,
NULL AS parentHash,
1 AS depth
FROM $filtered f
JOIN $source s USING (id)
WHERE f.parentId IS NULL
)
SELECT
g.id,
g.hash,
g.parentHash,
g.depth,
s.name,
f.value,
a.cumulativeValue
FROM _graph_scan!(
edges,
inits,
(hash, parentHash, depth),
(
SELECT
Expand All @@ -194,6 +275,8 @@ AS (
ORDER BY hash
);

-- Converts a table of hashes and paretn hashes into ids and parent
-- ids, grouping all hashes together.
CREATE PERFETTO MACRO _viz_flamegraph_merge_hashes(
hashed TableOrSubquery
)
Expand All @@ -215,6 +298,8 @@ AS (
GROUP BY hash
);

-- Performs a "layout" of nodes in the flamegraph relative to their
-- siblings.
CREATE PERFETTO MACRO _viz_flamegraph_local_layout(
merged TableOrSubquery
)
Expand All @@ -228,7 +313,7 @@ AS (
FROM $merged
WHERE cumulativeValue > 0
WINDOW win AS (
PARTITION BY parentId
PARTITION BY parentId, depth
ORDER BY cumulativeValue DESC
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
)
Expand All @@ -238,6 +323,8 @@ AS (
ORDER BY id
);

-- Walks the graph from root to leaf, propogating the layout of
-- parents to their children.
CREATE PERFETTO MACRO _viz_flamegraph_global_layout(
merged TableOrSubquery,
layout TableOrSubquery
Expand Down
44 changes: 33 additions & 11 deletions ui/src/core/query_flamegraph.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,7 @@ export class QueryFlamegraph implements m.ClassComponent<QueryFlamegraphAttrs> {
hideStack: [],
showFromFrame: [],
hideFrame: [],
pivot: undefined,
};
private attrs: QueryFlamegraphAttrs;
private selMonitor = new Monitor([() => this.attrs.metrics]);
Expand Down Expand Up @@ -143,13 +144,21 @@ async function computeFlamegraphTree(
engine: Engine,
dependencySql: string | undefined,
sql: string,
{showStack, hideStack, showFromFrame, hideFrame}: FlamegraphFilters,
{showStack, hideStack, showFromFrame, hideFrame, pivot}: FlamegraphFilters,
) {
// Pivot also essentially acts as a "show stack" filter so treat it like one.
const showStackAndPivot = [...showStack];
if (pivot !== undefined) {
showStackAndPivot.push(pivot);
}

const showStackFilter =
showStack.length === 0
showStackAndPivot.length === 0
? '0'
: showStack.map((x, i) => `((name like '%${x}%') << ${i})`).join(' | ');
const showStackBits = (1 << showStack.length) - 1;
: showStackAndPivot
.map((x, i) => `((name like '%${x}%') << ${i})`)
.join(' | ');
const showStackBits = (1 << showStackAndPivot.length) - 1;

const hideStackFilter =
hideStack.length === 0
Expand All @@ -169,6 +178,8 @@ async function computeFlamegraphTree(
? 'false'
: hideFrame.map((x) => `name like '%${x}%'`).join(' OR ');

const pivotFilter = pivot === undefined ? '0' : `name like '%${pivot}%'`;

if (dependencySql !== undefined) {
await engine.query(dependencySql);
}
Expand All @@ -190,7 +201,8 @@ async function computeFlamegraphTree(
(${hideStackFilter}),
(${showFromFrameFilter}),
(${hideFrameFilter}),
${1 << showStack.length}
(${pivotFilter}),
${1 << showStackAndPivot.length}
)
`,
),
Expand Down Expand Up @@ -229,12 +241,19 @@ async function computeFlamegraphTree(
`_flamegraph_hash_${uuid}`,
`
select *
from _viz_flamegraph_hash!(
from _viz_flamegraph_downwards_hash!(
_flamegraph_source_${uuid},
_flamegraph_filtered_${uuid},
_flamegraph_accumulated_${uuid},
${showStackBits}
_flamegraph_accumulated_${uuid}
)
union all
select *
from _viz_flamegraph_upwards_hash!(
_flamegraph_source_${uuid},
_flamegraph_filtered_${uuid},
_flamegraph_accumulated_${uuid}
)
order by hash
`,
),
);
Expand All @@ -243,7 +262,8 @@ async function computeFlamegraphTree(
engine,
`_flamegraph_merged_${uuid}`,
`
select * from _viz_flamegraph_merge_hashes!(
select *
from _viz_flamegraph_merge_hashes!(
_flamegraph_hash_${uuid}
)
`,
Expand Down Expand Up @@ -279,6 +299,7 @@ async function computeFlamegraphTree(
xEnd: NUM,
});
let allRootsCumulativeValue = 0;
let minDepth = 0;
let maxDepth = 0;
const nodes = [];
for (; it.valid(); it.next()) {
Expand All @@ -292,12 +313,13 @@ async function computeFlamegraphTree(
xStart: it.xStart,
xEnd: it.xEnd,
});
if (it.parentId === -1) {
if (it.depth === 1) {
allRootsCumulativeValue += it.cumulativeValue;
}
minDepth = Math.min(minDepth, it.depth);
maxDepth = Math.max(maxDepth, it.depth);
}
return {nodes, allRootsCumulativeValue, maxDepth};
return {nodes, allRootsCumulativeValue, minDepth, maxDepth};
}

export const USE_NEW_FLAMEGRAPH_IMPL = featureFlags.register({
Expand Down
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