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// Copyright 2009 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.
// Per-P malloc cache for small objects.
//
// See malloc.h for an overview.
package runtime
import "unsafe"
// dummy MSpan that contains no free objects.
var emptymspan mspan
func allocmcache() *mcache {
lock(&mheap_.lock)
c := (*mcache)(fixAlloc_Alloc(&mheap_.cachealloc))
unlock(&mheap_.lock)
memclr(unsafe.Pointer(c), unsafe.Sizeof(*c))
for i := 0; i < _NumSizeClasses; i++ {
c.alloc[i] = &emptymspan
}
// Set first allocation sample size.
rate := MemProfileRate
if rate > 0x3fffffff { // make 2*rate not overflow
rate = 0x3fffffff
}
if rate != 0 {
c.next_sample = int32(int(fastrand1()) % (2 * rate))
}
return c
}
func freemcache(c *mcache) {
systemstack(func() {
mCache_ReleaseAll(c)
stackcache_clear(c)
gcworkbuffree(c.gcworkbuf)
lock(&mheap_.lock)
purgecachedstats(c)
fixAlloc_Free(&mheap_.cachealloc, unsafe.Pointer(c))
unlock(&mheap_.lock)
})
}
// Gets a span that has a free object in it and assigns it
// to be the cached span for the given sizeclass. Returns this span.
func mCache_Refill(c *mcache, sizeclass int32) *mspan {
_g_ := getg()
_g_.m.locks++
// Return the current cached span to the central lists.
s := c.alloc[sizeclass]
if s.freelist != nil {
gothrow("refill on a nonempty span")
}
if s != &emptymspan {
s.incache = false
}
// Get a new cached span from the central lists.
s = mCentral_CacheSpan(&mheap_.central[sizeclass].mcentral)
if s == nil {
gothrow("out of memory")
}
if s.freelist == nil {
println(s.ref, (s.npages<<_PageShift)/s.elemsize)
gothrow("empty span")
}
c.alloc[sizeclass] = s
_g_.m.locks--
return s
}
func mCache_ReleaseAll(c *mcache) {
for i := 0; i < _NumSizeClasses; i++ {
s := c.alloc[i]
if s != &emptymspan {
mCentral_UncacheSpan(&mheap_.central[i].mcentral, s)
c.alloc[i] = &emptymspan
}
}
}
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