runtime: introduce helper persistentalloc() function

It is a caching wrapper around SysAlloc() that can allocate small chunks.
Use it for symtab allocations. Reduces number of symtab walks from 4 to 3
(reduces buildfuncs time from 10ms to 7.5ms on a large binary,
reduces initial heap size by 680K on the same binary).
Also can be used for type info allocation, itab allocation.
There are also several places in GC where we do the same thing,
they can be changed to use persistentalloc().
Also can be used in FixAlloc, because each instance of FixAlloc allocates
in 128K regions, which is too eager.

R=golang-dev, daniel.morsing, khr
CC=golang-dev
https://golang.org/cl/9805043

diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc
index b59693b5989cc9cda47ecb55e35765e527654ef4..cf18e8c9e59d0ef35018fcf373bf4e7e231bf353 100644 (file)
--- a/src/pkg/runtime/malloc.goc
+++ b/src/pkg/runtime/malloc.goc
@@ -484,6 +484,53 @@ runtime·MHeap_SysAlloc(MHeap *h, uintptr n)
        return p;
 }
 
+static struct
+{
+       Lock;
+       byte*   pos;
+       byte*   end;
+} persistent;
+
+enum
+{
+       PersistentAllocChunk    = 256<<10,
+       PersistentAllocMaxBlock = 64<<10,  // VM reservation granularity is 64K on windows
+};
+
+// Wrapper around SysAlloc that can allocate small chunks.
+// There is no associated free operation.
+// Intended for things like function/type/debug-related persistent data.
+// If align is 0, uses default align (currently 8).
+void*
+runtime·persistentalloc(uintptr size, uintptr align)
+{
+       byte *p;
+
+       if(align) {
+               if(align&(align-1))
+                       runtime·throw("persistentalloc: align is now a power of 2");
+               if(align > PageSize)
+                       runtime·throw("persistentalloc: align is too large");
+       } else
+               align = 8;
+       if(size >= PersistentAllocMaxBlock)
+               return runtime·SysAlloc(size);
+       runtime·lock(&persistent);
+       persistent.pos = (byte*)ROUND((uintptr)persistent.pos, align);
+       if(persistent.pos + size > persistent.end) {
+               persistent.pos = runtime·SysAlloc(PersistentAllocChunk);
+               if(persistent.pos == nil) {
+                       runtime·unlock(&persistent);
+                       runtime·throw("runtime: cannot allocate memory");
+               }
+               persistent.end = persistent.pos + PersistentAllocChunk;
+       }
+       p = persistent.pos;
+       persistent.pos += size;
+       runtime·unlock(&persistent);
+       return p; 
+}
+
 static Lock settype_lock;
 
 void

diff --git a/src/pkg/runtime/malloc.h b/src/pkg/runtime/malloc.h
index e732e3d15d652f2e24713f3053c6d98631ca8c37..99a1966071698ad6e3bbc1e0726b52a82453a82c 100644 (file)
--- a/src/pkg/runtime/malloc.h
+++ b/src/pkg/runtime/malloc.h
@@ -445,6 +445,7 @@ void        runtime·MHeap_MapBits(MHeap *h);
 void   runtime·MHeap_Scavenger(void);
 
 void*  runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed);
+void*  runtime·persistentalloc(uintptr size, uintptr align);
 int32  runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **s);
 void   runtime·gc(int32 force);
 void   runtime·markallocated(void *v, uintptr n, bool noptr);

diff --git a/src/pkg/runtime/symtab.c b/src/pkg/runtime/symtab.c
index 5edcb49bda8c5ed35affbb31264874099bd7a630..fdebe2cae374e72507858622f200f2483438dc4d 100644 (file)
--- a/src/pkg/runtime/symtab.c
+++ b/src/pkg/runtime/symtab.c
@@ -69,11 +69,6 @@ struct Sym
 
 static uintptr mainoffset;
 
-// A dynamically allocated string containing multiple substrings.
-// Individual strings are slices of hugestring.
-static String hugestring;
-static int32 hugestring_len;
-
 extern void main·main(void);
 
 static uintptr
@@ -288,7 +283,6 @@ makepath(byte *buf, int32 nbuf, byte *path)
        return p - buf;
 }
 
-// appends p to hugestring
 static String
 gostringn(byte *p, int32 l)
 {
@@ -296,13 +290,8 @@ gostringn(byte *p, int32 l)
 
        if(l == 0)
                return runtime·emptystring;
-       if(hugestring.str == nil) {
-               hugestring_len += l;
-               return runtime·emptystring;
-       }
-       s.str = hugestring.str + hugestring.len;
        s.len = l;
-       hugestring.len += s.len;
+       s.str = runtime·persistentalloc(l, 1);
        runtime·memmove(s.str, p, l);
        return s;
 }
@@ -333,8 +322,6 @@ dosrcline(Sym *sym)
        switch(sym->symtype) {
        case 't':
        case 'T':
-               if(hugestring.str == nil)
-                       break;
                if(runtime·strcmp(sym->name, (byte*)"etext") == 0)
                        break;
                f = &func[nfunc++];
@@ -559,11 +546,12 @@ buildfuncs(void)
        walksymtab(dofunc);
 
        // Initialize tables.
-       // Can use FlagNoPointers - all pointers either point into sections of the executable
-       // or point into hugestring.
-       func = runtime·mallocgc((nfunc+1)*sizeof func[0], FlagNoPointers, 0, 1);
+       // Memory obtained from runtime·persistentalloc() is not scanned by GC,
+       // this is fine because all pointers either point into sections of the executable
+       // or also obtained from persistentmalloc().
+       func = runtime·persistentalloc((nfunc+1)*sizeof func[0], 0);
        func[nfunc].entry = (uint64)etext;
-       fname = runtime·mallocgc(nfname*sizeof fname[0], FlagNoPointers, 0, 1);
+       fname = runtime·persistentalloc(nfname*sizeof fname[0], 0);
        nfunc = 0;
        lastvalue = 0;
        walksymtab(dofunc);
@@ -573,15 +561,9 @@ buildfuncs(void)
 
        // record src file and line info for each func
        files = runtime·malloc(maxfiles * sizeof(files[0]));
-       walksymtab(dosrcline);  // pass 1: determine hugestring_len
-       hugestring.str = runtime·mallocgc(hugestring_len, FlagNoPointers, 0, 0);
-       hugestring.len = 0;
-       walksymtab(dosrcline);  // pass 2: fill and use hugestring
+       walksymtab(dosrcline);
        files = nil;
 
-       if(hugestring.len != hugestring_len)
-               runtime·throw("buildfunc: problem in initialization procedure");
-
        m->nomemprof--;
 }