Improve unwind info code organisation

Split it in different files, added some more docs, and call the unwind
info optimisers directly.

Error handling improvements, more docs, and especially more tests coming
later. As this is a rather load-bearing part of the project, any issues
pop up pretty quickly in CI.

Test Plan
=========

CI

src/bpf/profiler_bindings.rs

@@ -5,7 +5,7 @@
 use plain::Plain;
 use std::ops::Add;
 
-use crate::unwind_info::CompactUnwindRow;
+use crate::unwind_info::types::CompactUnwindRow;
 
 include!(concat!(env!("OUT_DIR"), "/profiler_bindings.rs"));
 

src/main.rs

@@ -27,10 +27,8 @@ use lightswitch_metadata_provider::metadata_provider::ThreadSafeGlobalMetadataPr
 use lightswitch::profile::symbolize_profile;
 use lightswitch::profile::{fold_profile, to_pprof};
 use lightswitch::profiler::{Profiler, ProfilerConfig};
-use lightswitch::unwind_info::in_memory_unwind_info;
-use lightswitch::unwind_info::remove_redundant;
-use lightswitch::unwind_info::remove_unnecesary_markers;
-use lightswitch::unwind_info::UnwindInfoBuilder;
+use lightswitch::unwind_info::compact_unwind_info;
+use lightswitch::unwind_info::CompactUnwindInfoBuilder;
 use lightswitch_object::ObjectFile;
 
 const SAMPLE_FREQ_RANGE: RangeInclusive<usize> = 1..=1009;
@@ -237,10 +235,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     let args = Cli::parse();
 
     if let Some(path) = args.show_unwind_info {
-        let mut unwind_info = in_memory_unwind_info(&path).unwrap();
-        remove_unnecesary_markers(&mut unwind_info);
-        remove_redundant(&mut unwind_info);
-
+        let unwind_info = compact_unwind_info(&path).unwrap();
         for compact_row in unwind_info {
             let pc = compact_row.pc;
             let cfa_type = compact_row.cfa_type;
@@ -272,8 +267,8 @@ fn main() -> Result<(), Box<dyn Error>> {
     if let Some(path) = args.show_info {
         let objet_file = ObjectFile::new(&PathBuf::from(path.clone())).unwrap();
         println!("build id {:?}", objet_file.build_id());
-        let unwind_info: Result<UnwindInfoBuilder<'_>, anyhow::Error> =
-            UnwindInfoBuilder::with_callback(&path, |_| {});
+        let unwind_info: Result<CompactUnwindInfoBuilder<'_>, anyhow::Error> =
+            CompactUnwindInfoBuilder::with_callback(&path, |_| {});
         println!("unwind info {:?}", unwind_info.unwrap().process());
 
         return Ok(());

src/profiler.rs

@@ -33,9 +33,9 @@ use crate::bpf::tracers_bindings::*;
 use crate::bpf::tracers_skel::{TracersSkel, TracersSkelBuilder};
 use crate::collector::*;
 use crate::perf_events::setup_perf_event;
+use crate::unwind_info::compact_unwind_info;
 use crate::unwind_info::log_unwind_info_sections;
-use crate::unwind_info::CompactUnwindRow;
-use crate::unwind_info::{in_memory_unwind_info, remove_redundant, remove_unnecesary_markers};
+use crate::unwind_info::types::CompactUnwindRow;
 use crate::util::{get_online_cpus, summarize_address_range};
 use lightswitch_object::ElfLoad;
 use lightswitch_object::{BuildId, ExecutableId, ObjectFile};
@@ -1140,7 +1140,7 @@ impl Profiler<'_> {
         executable_id: u64,
         bucket_id: u32,
     ) {
-        let pages = crate::unwind_info::to_pages(unwind_info);
+        let pages = crate::unwind_info::pages::to_pages(unwind_info);
         for page in pages {
             let page_key = page_key_t {
                 file_offset: page.address,
@@ -1445,40 +1445,32 @@ impl Profiler<'_> {
             )
             .entered();
 
-            let mut found_unwind_info: Vec<CompactUnwindRow>;
-
-            match in_memory_unwind_info(&executable_path.to_string_lossy()) {
-                Ok(unwind_info) => {
-                    found_unwind_info = unwind_info;
-                }
-                Err(e) => {
-                    let executable_path_str = executable.path.to_string_lossy();
-                    let known_naughty = executable_path_str.contains("libicudata");
-
-                    // tracing doesn't support a level chosen at runtime: https://github.com/tokio-rs/tracing/issues/2730
-                    if known_naughty {
-                        debug!(
-                            "failed to get unwind information for {} with {}",
-                            executable_path_str, e
-                        );
-                    } else {
-                        info!(
-                            "failed to get unwind information for {} with {}",
-                            executable_path_str, e
-                        );
+            let found_unwind_info: Vec<CompactUnwindRow> =
+                match compact_unwind_info(&executable_path.to_string_lossy()) {
+                    Ok(unwind_info) => unwind_info,
+                    Err(e) => {
+                        let executable_path_str = executable.path.to_string_lossy();
+                        let known_naughty = executable_path_str.contains("libicudata");
+
+                        // tracing doesn't support a level chosen at runtime: https://github.com/tokio-rs/tracing/issues/2730
+                        if known_naughty {
+                            debug!(
+                                "failed to get unwind information for {} with {}",
+                                executable_path_str, e
+                            );
+                        } else {
+                            info!(
+                                "failed to get unwind information for {} with {}",
+                                executable_path_str, e
+                            );
 
-                        if let Err(e) = log_unwind_info_sections(&executable_path) {
-                            warn!("log_unwind_info_sections failed with {}", e);
+                            if let Err(e) = log_unwind_info_sections(&executable_path) {
+                                warn!("log_unwind_info_sections failed with {}", e);
+                            }
                         }
+                        continue;
                     }
-                    continue;
-                }
-            }
-            span.exit();
-
-            let span: span::EnteredSpan = span!(Level::DEBUG, "optimize unwind info").entered();
-            remove_unnecesary_markers(&mut found_unwind_info);
-            remove_redundant(&mut found_unwind_info);
+                };
             span.exit();
 
             // Evicting object files can get complicated real quick... this can be implemented once