Exclude profiler

src/main.rs

@@ -220,6 +220,9 @@ struct Cli {
         help = "Derived from constant MAX_PROCESSES"
     )]
     mapsize_rate_limits: u32,
+    // Exclude myself from profiling
+    #[arg(long, help = "Do not profile the profiler (myself)")]
+    exclude_self: bool,
 }
 
 /// Exit the main thread if any thread panics. We prefer this behaviour because pretty much every
@@ -308,6 +311,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         mapsize_unwind_info_chunks: args.mapsize_unwind_info_chunks,
         mapsize_unwind_tables: args.mapsize_unwind_tables,
         mapsize_rate_limits: args.mapsize_rate_limits,
+        exclude_self: args.exclude_self,
     };
 
     let (stop_signal_sender, stop_signal_receive) = bounded(1);
@@ -399,8 +403,7 @@ mod tests {
         cmd.assert().success();
         let actual = String::from_utf8(cmd.unwrap().stdout).unwrap();
         insta::assert_yaml_snapshot!(actual, @r###"
-        ---
-        "Usage: lightswitch [OPTIONS]\n\nOptions:\n      --pids <PIDS>\n          Specific PIDs to profile\n\n      --tids <TIDS>\n          Specific TIDs to profile (these can be outside the PIDs selected above)\n\n      --show-unwind-info <PATH_TO_BINARY>\n          Show unwind info for given binary\n\n      --show-info <PATH_TO_BINARY>\n          Show build ID for given binary\n\n  -D, --duration <DURATION>\n          How long this agent will run in seconds\n          \n          [default: 18446744073709551615]\n\n      --libbpf-logs\n          Enable libbpf logs. This includes the BPF verifier output\n\n      --bpf-logging\n          Enable BPF programs logging\n\n      --logging <LOGGING>\n          Set lightswitch's logging level\n          \n          [default: info]\n          [possible values: trace, debug, info, warn, error]\n\n      --sample-freq <SAMPLE_FREQ_IN_HZ>\n          Per-CPU Sampling Frequency in Hz\n          \n          [default: 19]\n\n      --profile-format <PROFILE_FORMAT>\n          Output file for Flame Graph in SVG format\n          \n          [default: flame-graph]\n          [possible values: none, flame-graph, pprof]\n\n      --profile-name <PROFILE_NAME>\n          Name for the generated profile\n\n      --sender <SENDER>\n          Where to write the profile\n          \n          [default: local-disk]\n\n          Possible values:\n          - none:       Discard the profile. Used for kernel tests\n          - local-disk\n          - remote\n\n      --perf-buffer-bytes <PERF_BUFFER_BYTES>\n          Size of each profiler perf buffer, in bytes (must be a power of 2)\n          \n          [default: 524288]\n\n      --mapsize-info\n          Print eBPF map sizes after creation\n\n      --mapsize-stacks <MAPSIZE_STACKS>\n          max number of individual stacks to capture before aggregation\n          \n          [default: 100000]\n\n      --mapsize-aggregated-stacks <MAPSIZE_AGGREGATED_STACKS>\n          Derived from constant MAX_AGGREGATED_STACKS_ENTRIES - max number of unique stacks after aggregation\n          \n          [default: 10000]\n\n      --mapsize-unwind-info-chunks <MAPSIZE_UNWIND_INFO_CHUNKS>\n          max number of chunks allowed inside a shard\n          \n          [default: 5000]\n\n      --mapsize-unwind-tables <MAPSIZE_UNWIND_TABLES>\n          Derived from constant MAX_UNWIND_INFO_SHARDS\n          \n          [default: 65]\n\n      --mapsize-rate-limits <MAPSIZE_RATE_LIMITS>\n          Derived from constant MAX_PROCESSES\n          \n          [default: 5000]\n\n  -h, --help\n          Print help (see a summary with '-h')\n"
+        "Usage: lightswitch [OPTIONS]\n\nOptions:\n      --pids <PIDS>\n          Specific PIDs to profile\n\n      --tids <TIDS>\n          Specific TIDs to profile (these can be outside the PIDs selected above)\n\n      --show-unwind-info <PATH_TO_BINARY>\n          Show unwind info for given binary\n\n      --show-info <PATH_TO_BINARY>\n          Show build ID for given binary\n\n  -D, --duration <DURATION>\n          How long this agent will run in seconds\n          \n          [default: 18446744073709551615]\n\n      --libbpf-logs\n          Enable libbpf logs. This includes the BPF verifier output\n\n      --bpf-logging\n          Enable BPF programs logging\n\n      --logging <LOGGING>\n          Set lightswitch's logging level\n          \n          [default: info]\n          [possible values: trace, debug, info, warn, error]\n\n      --sample-freq <SAMPLE_FREQ_IN_HZ>\n          Per-CPU Sampling Frequency in Hz\n          \n          [default: 19]\n\n      --profile-format <PROFILE_FORMAT>\n          Output file for Flame Graph in SVG format\n          \n          [default: flame-graph]\n          [possible values: none, flame-graph, pprof]\n\n      --profile-name <PROFILE_NAME>\n          Name for the generated profile\n\n      --sender <SENDER>\n          Where to write the profile\n          \n          [default: local-disk]\n\n          Possible values:\n          - none:       Discard the profile. Used for kernel tests\n          - local-disk\n          - remote\n\n      --perf-buffer-bytes <PERF_BUFFER_BYTES>\n          Size of each profiler perf buffer, in bytes (must be a power of 2)\n          \n          [default: 524288]\n\n      --mapsize-info\n          Print eBPF map sizes after creation\n\n      --mapsize-stacks <MAPSIZE_STACKS>\n          max number of individual stacks to capture before aggregation\n          \n          [default: 100000]\n\n      --mapsize-aggregated-stacks <MAPSIZE_AGGREGATED_STACKS>\n          Derived from constant MAX_AGGREGATED_STACKS_ENTRIES - max number of unique stacks after aggregation\n          \n          [default: 10000]\n\n      --mapsize-unwind-info-chunks <MAPSIZE_UNWIND_INFO_CHUNKS>\n          max number of chunks allowed inside a shard\n          \n          [default: 5000]\n\n      --mapsize-unwind-tables <MAPSIZE_UNWIND_TABLES>\n          Derived from constant MAX_UNWIND_INFO_SHARDS\n          \n          [default: 65]\n\n      --mapsize-rate-limits <MAPSIZE_RATE_LIMITS>\n          Derived from constant MAX_PROCESSES\n          \n          [default: 5000]\n\n      --exclude-self\n          Do not profile the profiler (myself)\n\n  -h, --help\n          Print help (see a summary with '-h')\n"
         "###);
     }
 

src/profiler.rs

@@ -197,6 +197,8 @@ pub struct Profiler<'bpf> {
     // Size of each perf buffer, in bytes
     perf_buffer_bytes: usize,
     session_duration: Duration,
+    // Whether the profiler (this process) should be excluded from profiling
+    exclude_self: bool,
 }
 
 // Static config
@@ -326,6 +328,7 @@ pub struct ProfilerConfig {
     pub mapsize_unwind_info_chunks: u32,
     pub mapsize_unwind_tables: u32,
     pub mapsize_rate_limits: u32,
+    pub exclude_self: bool,
 }
 
 // Note that we normally pass in the defaults from Clap, and we don't want
@@ -346,6 +349,7 @@ impl Default for ProfilerConfig {
             mapsize_unwind_info_chunks: 5000,
             mapsize_unwind_tables: 65,
             mapsize_rate_limits: 5000,
+            exclude_self: false,
         }
     }
 }
@@ -398,6 +402,7 @@ impl Profiler<'_> {
             .lightswitch_config
             .verbose_logging
             .write(profiler_config.bpf_logging);
+        let exclude_self = profiler_config.exclude_self;
         let bpf = open_skel.load().expect("load skel");
         info!("native unwinder BPF program loaded");
         let native_unwinder_maps = bpf.maps();
@@ -491,6 +496,7 @@ impl Profiler<'_> {
             sample_freq,
             perf_buffer_bytes,
             session_duration: Duration::from_secs(5),
+            exclude_self,
         }
     }
 
@@ -1216,6 +1222,10 @@ impl Profiler<'_> {
     }
 
     fn should_profile(&self, pid: i32) -> bool {
+        if self.exclude_self && (pid == std::process::id().try_into().unwrap()) {
+            return false;
+        }
+
         if self.filter_pids.is_empty() {
             return true;
         }