90 lines
1.9 KiB
Go
90 lines
1.9 KiB
Go
// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package pprof
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import "unsafe"
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// A profMap is a map from (stack, tag) to mapEntry.
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// It grows without bound, but that's assumed to be OK.
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type profMap struct {
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hash map[uintptr]*profMapEntry
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all *profMapEntry
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last *profMapEntry
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free []profMapEntry
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freeStk []uintptr
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}
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// A profMapEntry is a single entry in the profMap.
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type profMapEntry struct {
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nextHash *profMapEntry // next in hash list
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nextAll *profMapEntry // next in list of all entries
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stk []uintptr
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tag unsafe.Pointer
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count int64
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}
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func (m *profMap) lookup(stk []uint64, tag unsafe.Pointer) *profMapEntry {
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// Compute hash of (stk, tag).
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h := uintptr(0)
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for _, x := range stk {
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h = h<<8 | (h >> (8 * (unsafe.Sizeof(h) - 1)))
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h += uintptr(x) * 41
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}
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h = h<<8 | (h >> (8 * (unsafe.Sizeof(h) - 1)))
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h += uintptr(tag) * 41
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// Find entry if present.
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var last *profMapEntry
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Search:
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for e := m.hash[h]; e != nil; last, e = e, e.nextHash {
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if len(e.stk) != len(stk) || e.tag != tag {
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continue
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}
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for j := range stk {
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if e.stk[j] != uintptr(stk[j]) {
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continue Search
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}
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}
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// Move to front.
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if last != nil {
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last.nextHash = e.nextHash
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e.nextHash = m.hash[h]
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m.hash[h] = e
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}
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return e
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}
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// Add new entry.
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if len(m.free) < 1 {
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m.free = make([]profMapEntry, 128)
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}
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e := &m.free[0]
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m.free = m.free[1:]
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e.nextHash = m.hash[h]
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e.tag = tag
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if len(m.freeStk) < len(stk) {
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m.freeStk = make([]uintptr, 1024)
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}
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e.stk = m.freeStk[:len(stk)]
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m.freeStk = m.freeStk[len(stk):]
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for j := range stk {
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e.stk[j] = uintptr(stk[j])
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}
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if m.hash == nil {
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m.hash = make(map[uintptr]*profMapEntry)
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}
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m.hash[h] = e
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if m.all == nil {
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m.all = e
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m.last = e
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} else {
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m.last.nextAll = e
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m.last = e
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}
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return e
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}
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