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[#15990] docdb: Update /pprof/heap to work with new tcmalloc.
Summary:
The new tcmalloc (--use-google-tcmalloc) uses a sampling-based profiler (and got rid of the old all-allocation profiler).
This diff updates /pprof/heap to use the sampling profiler. The output of this endpoint was previously parsed by yb-prof, but since the new format is structured, it's easy enough to output directly as a table (and makes testability and symbolization easier).
There are 3 arguments that can passed to passed to /pprof/heap as url arguments:
1. `seconds` controls how long to profile for
2. `sample_freq_bytes` controls how often we sample for allocations.
3. `only_growth` controls whether we output only call stacks for allocations for which we did not observe a corresponding deallocation. Pass only growth if you want the equivalent of `yb-prof`'s in_use_bytes.html, and do not pass it if you want the equivalent of `alloc_bytes.html`. NB: Both alloc_bytes.html and in_use_bytes were essentially the same data, just sorted differently (i.e. both had the allocated bytes and in use bytes for each call stack). In the new endpoints, I kept the information separate (if we want this back we can change it though).
For example, if you want to profile allocations for 60s, sampling every 2MiB, you would go to (for a tserver):
```
IP:9000/pprof/heap?seconds=60&sample_freq_bytes=2000000
```
If you wanted the same as above but with only allocations that were not deallocated you would go to:
```
IP:9000/pprof/heap?seconds=60&sample_freq_bytes=2000000&only_growth=true
```
Example output for the /pprof/heap endpoint:
{F34511}
{F34512}
This diff also adds a /pprof/heap_snapshot endpoint that gives an instantaneous view of the heap at either the time of peak heap usage (if the `peak_heap` url argument is true) or at the current time (if `peak_heap` is false). For this endpoint to be used, the `enable_process_lifetime_heap_profiling` gflag must have been set to true since the last restart (samples are taken according to the frequency in the new `profiler_sample_freq_bytes` gflag).
Test Plan: Manually tested by running `CassandraBatchTimeseries` against a cluster and verifying that for `only_growth = True` we only see stacks that were not deallocated (rocksdb inserts), and with `only_growth = False` we see all stacks.
Reviewers: amitanand, bogdan, esheng
Reviewed By: esheng
Subscribers: ybase
Differential Revision: https://phabricator.dev.yugabyte.com/D22780- Loading branch information
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