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flameGraph

聚合函数，它使用堆栈跟踪列表构建 火焰图。输出一个字符串数组，该数组可由 flamegraph.pl 实用程序 使用，以渲染火焰图的 SVG。

语法​

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

参数​

  • traces — 堆栈跟踪。数组(UInt64)。
  • size — 用于内存分析的分配大小。（可选 - 默认为 1）。UInt64。
  • ptr — 分配地址。（可选 - 默认为 0）。UInt64。
注意

在 ptr != 0 的情况下，flameGraph 将使用相同的大小和 ptr 映射分配（size > 0）和释放（size < 0）。仅显示未释放的分配。未映射的释放将被忽略。

返回值​

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，显示所有分配​

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，显示在查询上下文中未释放的分配​

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，显示在固定时间点的活动分配​

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');
  • 3 - 在固定时间点固定活动分配
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 - 在固定时间点查找释放
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