flameGraph

引入版本：v23.8

使用堆栈跟踪列表构建一个火焰图（flamegraph）。输出一个字符串数组，可供 flamegraph.pl 工具使用，用于渲染该火焰图的 SVG。

注意

在 ptr != 0 的情况下，flameGraph 会将具有相同 size 和 ptr 的分配（size > 0）与释放（size < 0）对应起来。只显示尚未被释放的分配。未对应上的释放操作会被忽略。

语法

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

参数

traces — 堆栈回溯。Array(UInt64)
size — 可选。用于内存分析的分配大小（默认值为 1）。UInt64
ptr — 可选。分配地址（默认值为 0）。UInt64

返回值

返回一个字符串数组，用于配合 flamegraph.pl 实用工具使用。Array(String)

示例

基于 CPU 查询分析器构建火焰图

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;

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

基于内存查询分析器构建火焰图，展示所有内存分配情况

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;

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

基于内存查询分析器构建火焰图，用于展示尚未释放的内存分配

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;

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构建火焰图，在某个固定时间点展示活动内存分配情况

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. Memory usage per second
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. Find a time point with maximal memory usage
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');

-- 3. Fix active allocations at fixed point of time
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. Find deallocations at fixed point of time
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

flameGraph​

flameGraph