flameGraph

用于根据 stacktraces 列表构建火焰图的聚合函数。

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flameGraph

引入版本：v23.8.0

根据 stacktraces 列表构建一个 火焰图。 输出一个字符串数组，可供 flamegraph.pl 工具用于渲染火焰图的 SVG。

在 ptr != 0 的情况下，flameGraph 会将 size 和 ptr 相同的内存分配 (size > 0) 与释放 (size < 0) 进行映射。 仅显示尚未释放的内存分配。 未映射到的释放会被忽略。

语法

flameGraph(traces[, size[, ptr]])

参数

• traces — 一条调用栈，可以是原始地址，也可以是已解析符号的字符串 (例如 arrayMap(addressToSymbol, trace)) 。Array(UInt64) 或 Array(String)
• size — 可选。用于内存性能分析的分配大小 (默认值为 1) 。UInt64
• ptr — 可选。分配地址 (默认值为 0) 。UInt64

返回值

返回一个供 flamegraph.pl 工具使用的字符串数组。Array(String)

示例

基于 CPU 查询分析器构建火焰图

Query

SET query_profiler_cpu_time_period_ns=10000000;
SELECT SearchPhrase, COUNT(DISTINCT UserID) AS u FROM hits WHERE SearchPhrase <> '' GROUP BY SearchPhrase ORDER BY u DESC LIMIT 10;

Response

clickhouse client --allow_introspection_functions=1 -q "select arrayJoin(flameGraph(arrayReverse(trace))) from system.trace_log where trace_type = 'CPU' and query_id = 'xxx'" | ~/dev/FlameGraph/flamegraph.pl  > flame_cpu.svg

使用内存查询分析器构建显示所有内存分配的 火焰图

Query

SET memory_profiler_sample_probability=1, max_untracked_memory=1;
SELECT SearchPhrase, COUNT(DISTINCT UserID) AS u FROM hits WHERE SearchPhrase <> '' GROUP BY SearchPhrase ORDER BY u DESC LIMIT 10;

Response

clickhouse client --allow_introspection_functions=1 -q "select arrayJoin(flameGraph(trace, size)) from system.trace_log where trace_type = 'MemorySample' and query_id = 'xxx'" | ~/dev/FlameGraph/flamegraph.pl --countname=bytes --color=mem > flame_mem.svg

根据内存查询分析器构建的 火焰图，显示未释放的内存分配

Query

SET memory_profiler_sample_probability=1, max_untracked_memory=1, use_uncompressed_cache=1, merge_tree_max_rows_to_use_cache=100000000000, merge_tree_max_bytes_to_use_cache=1000000000000;
SELECT SearchPhrase, COUNT(DISTINCT UserID) AS u FROM hits WHERE SearchPhrase <> '' GROUP BY SearchPhrase ORDER BY u DESC LIMIT 10;

Response

clickhouse client --allow_introspection_functions=1 -q "SELECT arrayJoin(flameGraph(trace, size, ptr)) FROM system.trace_log WHERE trace_type = 'MemorySample' AND query_id = 'xxx'" | ~/dev/FlameGraph/flamegraph.pl --countname=bytes --color=mem > flame_mem_untracked.svg

基于内存查询分析器生成火焰图，显示某一固定时刻的活跃分配

Query

SET memory_profiler_sample_probability=1, max_untracked_memory=1;
SELECT SearchPhrase, COUNT(DISTINCT UserID) AS u FROM hits WHERE SearchPhrase <> '' GROUP BY SearchPhrase ORDER BY u DESC LIMIT 10;

-- 1. 每秒内存使用量
SELECT event_time, m, formatReadableSize(max(s) AS m) FROM (SELECT event_time, sum(size) OVER (ORDER BY event_time) AS s FROM system.trace_log WHERE query_id = 'xxx' AND trace_type = 'MemorySample') GROUP BY event_time ORDER BY event_time;

-- 2. 找到内存使用量最大的时间点
SELECT argMax(event_time, s), max(s) FROM (SELECT event_time, sum(size) OVER (ORDER BY event_time) AS s FROM system.trace_log WHERE query_id = 'xxx' AND trace_type = 'MemorySample');

Response

-- 3. 修复特定时间点的活跃分配
clickhouse client --allow_introspection_functions=1 -q "SELECT arrayJoin(flameGraph(trace, size, ptr)) FROM (SELECT * FROM system.trace_log WHERE trace_type = 'MemorySample' AND query_id = 'xxx' AND event_time <= 'yyy' ORDER BY event_time\)\" | ~/dev/FlameGraph/flamegraph.pl --countname=bytes --color=mem > flame_mem_time_point_pos.svg

-- 4. 查找特定时间点的释放
clickhouse client --allow_introspection_functions=1 -q "SELECT arrayJoin(flameGraph(trace, -size, ptr)) FROM (SELECT * FROM system.trace_log WHERE trace_type = 'MemorySample' AND query_id = 'xxx' AND event_time > 'yyy' ORDER BY event_time desc\)\" | ~/dev/FlameGraph/flamegraph.pl --countname=bytes --color=mem > flame_mem_time_point_neg.svg