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runtime: zero 2-word memory blocks in-place 

Currently for 2-word blocks we set the flag to clear the flag. Makes no sense.
In particular on 32-bits we call memclr always.

R=golang-codereviews, dave, iant
CC=golang-codereviews, khr, rsc
https://golang.org/cl/41170044
This commit is contained in:
Dmitriy Vyukov 2014-01-21 10:53:51 +04:00
parent b039abfc3e
commit d5a36cd6bb
2 changed files with 8 additions and 4 deletions
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6
src/pkg/runtime/malloc.goc
View File

@ -75,7 +75,7 @@ runtime·mallocgc(uintptr size, uintptr typ, uint32 flag)
if(!(flag & FlagNoZero)) { if(!(flag & FlagNoZero)) {
v->next = nil; v->next = nil;
// block is zeroed iff second word is zero ... // block is zeroed iff second word is zero ...
if(size > sizeof(uintptr) && ((uintptr*)v)[1] != 0) if(size > 2*sizeof(uintptr) && ((uintptr*)v)[1] != 0)
runtime·memclr((byte*)v, size); runtime·memclr((byte*)v, size);
} }
c->local_cachealloc += size; c->local_cachealloc += size;
@ -205,8 +205,10 @@ runtime·free(void *v)
c->local_largefree += size; c->local_largefree += size;
} else { } else {
// Small object. // Small object.
if(size > sizeof(uintptr)) if(size > 2*sizeof(uintptr))
((uintptr*)v)[1] = (uintptr)0xfeedfeedfeedfeedll; // mark as "needs to be zeroed" ((uintptr*)v)[1] = (uintptr)0xfeedfeedfeedfeedll; // mark as "needs to be zeroed"
else if(size > sizeof(uintptr))
((uintptr*)v)[1] = 0;
// Must mark v freed before calling MCache_Free: // Must mark v freed before calling MCache_Free:
// it might coalesce v and other blocks into a bigger span // it might coalesce v and other blocks into a bigger span
// and change the bitmap further. // and change the bitmap further.

6
src/pkg/runtime/mgc0.c
View File

@ -1867,9 +1867,11 @@ sweepspan(ParFor *desc, uint32 idx)
*(byte*)type_data = 0; *(byte*)type_data = 0;
break; break;
} }
if(size > sizeof(uintptr)) if(size > 2*sizeof(uintptr))
((uintptr*)p)[1] = (uintptr)0xdeaddeaddeaddeadll; // mark as "needs to be zeroed" ((uintptr*)p)[1] = (uintptr)0xdeaddeaddeaddeadll; // mark as "needs to be zeroed"
else if(size > sizeof(uintptr))
((uintptr*)p)[1] = 0;
end->next = (MLink*)p; end->next = (MLink*)p;
end = (MLink*)p; end = (MLink*)p;
nfree++; nfree++;