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Source file src/runtime/pprof/internal/profile/prune.go

Documentation: runtime/pprof/internal/profile

  // Copyright 2014 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // Implements methods to remove frames from profiles.
  
  package profile
  
  import (
  	"fmt"
  	"regexp"
  )
  
  // Prune removes all nodes beneath a node matching dropRx, and not
  // matching keepRx. If the root node of a Sample matches, the sample
  // will have an empty stack.
  func (p *Profile) Prune(dropRx, keepRx *regexp.Regexp) {
  	prune := make(map[uint64]bool)
  	pruneBeneath := make(map[uint64]bool)
  
  	for _, loc := range p.Location {
  		var i int
  		for i = len(loc.Line) - 1; i >= 0; i-- {
  			if fn := loc.Line[i].Function; fn != nil && fn.Name != "" {
  				funcName := fn.Name
  				// Account for leading '.' on the PPC ELF v1 ABI.
  				if funcName[0] == '.' {
  					funcName = funcName[1:]
  				}
  				if dropRx.MatchString(funcName) {
  					if keepRx == nil || !keepRx.MatchString(funcName) {
  						break
  					}
  				}
  			}
  		}
  
  		if i >= 0 {
  			// Found matching entry to prune.
  			pruneBeneath[loc.ID] = true
  
  			// Remove the matching location.
  			if i == len(loc.Line)-1 {
  				// Matched the top entry: prune the whole location.
  				prune[loc.ID] = true
  			} else {
  				loc.Line = loc.Line[i+1:]
  			}
  		}
  	}
  
  	// Prune locs from each Sample
  	for _, sample := range p.Sample {
  		// Scan from the root to the leaves to find the prune location.
  		// Do not prune frames before the first user frame, to avoid
  		// pruning everything.
  		foundUser := false
  		for i := len(sample.Location) - 1; i >= 0; i-- {
  			id := sample.Location[i].ID
  			if !prune[id] && !pruneBeneath[id] {
  				foundUser = true
  				continue
  			}
  			if !foundUser {
  				continue
  			}
  			if prune[id] {
  				sample.Location = sample.Location[i+1:]
  				break
  			}
  			if pruneBeneath[id] {
  				sample.Location = sample.Location[i:]
  				break
  			}
  		}
  	}
  }
  
  // RemoveUninteresting prunes and elides profiles using built-in
  // tables of uninteresting function names.
  func (p *Profile) RemoveUninteresting() error {
  	var keep, drop *regexp.Regexp
  	var err error
  
  	if p.DropFrames != "" {
  		if drop, err = regexp.Compile("^(" + p.DropFrames + ")$"); err != nil {
  			return fmt.Errorf("failed to compile regexp %s: %v", p.DropFrames, err)
  		}
  		if p.KeepFrames != "" {
  			if keep, err = regexp.Compile("^(" + p.KeepFrames + ")$"); err != nil {
  				return fmt.Errorf("failed to compile regexp %s: %v", p.KeepFrames, err)
  			}
  		}
  		p.Prune(drop, keep)
  	}
  	return nil
  }
  

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