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Re: parallelized 'ld'?
- From: DJ Delorie <dj at redhat dot com>
- To: cynbe at muq dot org
- Cc: binutils at sources dot redhat dot com, asmundak at cisco dot com
- Date: Tue, 26 Aug 2003 14:04:31 -0400
- Subject: Re: parallelized 'ld'?
- References: <200307150234.h6F2YsNW028337@tully.CS.Berkeley.EDU> <87d6f63jes.fsf@muq.org>
> Automatically expanding hashtables when they reach ludicrous overload
> levels isn't that hard -- I've been doing it without a second thought
> in everything I've written for the last twenty years. No?
Here's a quick patch to implement that, at least in a naive way. See
if this makes a difference in link speed (at least for large apps; I
don't notice a significant speedup for linking cc1) and if it's worth
the effort I'll document it, clean it up, test it, and commit it.
Index: bfd/bfd-in.h
===================================================================
RCS file: /cvs/src/src/bfd/bfd-in.h,v
retrieving revision 1.64
diff -p -2 -r1.64 bfd/bfd-in.h
*** bfd/bfd-in.h 11 Jul 2003 14:59:40 -0000 1.64
--- bfd/bfd-in.h 26 Aug 2003 17:58:40 -0000
*************** struct bfd_hash_table
*** 386,389 ****
--- 386,391 ----
/* The number of slots in the hash table. */
unsigned int size;
+ /* The number of entries in the hash table. */
+ unsigned int count;
/* A function used to create new elements in the hash table. The
first entry is itself a pointer to an element. When this
Index: bfd/bfd-in2.h
===================================================================
RCS file: /cvs/src/src/bfd/bfd-in2.h,v
retrieving revision 1.233
diff -p -2 -r1.233 bfd/bfd-in2.h
*** bfd/bfd-in2.h 8 Aug 2003 10:14:50 -0000 1.233
--- bfd/bfd-in2.h 26 Aug 2003 17:58:40 -0000
*************** struct bfd_hash_table
*** 393,396 ****
--- 393,398 ----
/* The number of slots in the hash table. */
unsigned int size;
+ /* The number of entries in the hash table. */
+ unsigned int count;
/* A function used to create new elements in the hash table. The
first entry is itself a pointer to an element. When this
Index: bfd/hash.c
===================================================================
RCS file: /cvs/src/src/bfd/hash.c,v
retrieving revision 1.9
diff -p -2 -r1.9 bfd/hash.c
*** bfd/hash.c 30 Nov 2002 08:39:39 -0000 1.9
--- bfd/hash.c 26 Aug 2003 17:58:41 -0000
*************** SUBSUBSECTION
*** 296,300 ****
/* The default number of entries to use when creating a hash table. */
! #define DEFAULT_SIZE (4051)
/* Create a new hash table, given a number of entries. */
--- 296,365 ----
/* The default number of entries to use when creating a hash table. */
! #define DEFAULT_SIZE (4093)
!
! /* The following function returns a nearest prime number which is
! greater than N, and near a power of two. Copied from libiberty. */
!
! static unsigned long
! higher_prime_number (n)
! unsigned long n;
! {
! /* These are primes that are near, but slightly smaller than, a
! power of two. */
! static const unsigned long primes[] = {
! (unsigned long) 7,
! (unsigned long) 13,
! (unsigned long) 31,
! (unsigned long) 61,
! (unsigned long) 127,
! (unsigned long) 251,
! (unsigned long) 509,
! (unsigned long) 1021,
! (unsigned long) 2039,
! (unsigned long) 4093,
! (unsigned long) 8191,
! (unsigned long) 16381,
! (unsigned long) 32749,
! (unsigned long) 65521,
! (unsigned long) 131071,
! (unsigned long) 262139,
! (unsigned long) 524287,
! (unsigned long) 1048573,
! (unsigned long) 2097143,
! (unsigned long) 4194301,
! (unsigned long) 8388593,
! (unsigned long) 16777213,
! (unsigned long) 33554393,
! (unsigned long) 67108859,
! (unsigned long) 134217689,
! (unsigned long) 268435399,
! (unsigned long) 536870909,
! (unsigned long) 1073741789,
! (unsigned long) 2147483647,
! /* 4294967291L */
! ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
! };
!
! const unsigned long *low = &primes[0];
! const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
!
! while (low != high)
! {
! const unsigned long *mid = low + (high - low) / 2;
! if (n >= *mid)
! low = mid + 1;
! else
! high = mid;
! }
!
! /* If we've run out of primes, abort. */
! if (n > *low)
! {
! fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
! abort ();
! }
!
! return *low;
! }
/* Create a new hash table, given a number of entries. */
*************** bfd_hash_table_init_n (table, newfunc, s
*** 327,330 ****
--- 392,396 ----
memset ((PTR) table->table, 0, alloc);
table->size = size;
+ table->count = 0;
table->newfunc = newfunc;
return TRUE;
*************** bfd_hash_lookup (table, string, create,
*** 397,400 ****
--- 463,467 ----
if (hashp == (struct bfd_hash_entry *) NULL)
return (struct bfd_hash_entry *) NULL;
+ table->count ++;
if (copy)
{
*************** bfd_hash_lookup (table, string, create,
*** 415,418 ****
--- 482,514 ----
hashp->next = table->table[index];
table->table[index] = hashp;
+
+ if (table->count > table->size * 3 / 4)
+ {
+ int newsize = higher_prime_number (table->size);
+ struct bfd_hash_entry **newtable, *he;
+ unsigned int hi;
+ unsigned int alloc;
+
+ alloc = newsize * sizeof (struct bfd_hash_entry *);
+
+ fprintf(stderr, "dj: expand count %d size %d to %d\n", table->count, table->size, newsize);
+
+ newtable = ((struct bfd_hash_entry **)
+ objalloc_alloc ((struct objalloc *) table->memory, alloc));
+ memset ((PTR) newtable, 0, alloc);
+
+ for (hi = 0; hi < table->size; hi ++)
+ while (table->table[hi])
+ {
+ int index;
+ he = table->table[hi];
+ table->table[hi] = he->next;
+ index = he->hash % newsize;
+ he->next = newtable[index];
+ newtable[index] = he;
+ }
+ table->table = newtable;
+ table->size = newsize;
+ }
return hashp;
Index: libiberty/hashtab.c
===================================================================
RCS file: /cvs/src/src/libiberty/hashtab.c,v
retrieving revision 1.23
diff -p -2 -r1.23 libiberty/hashtab.c
*** libiberty/hashtab.c 19 Jun 2003 20:05:36 -0000 1.23
--- libiberty/hashtab.c 26 Aug 2003 17:58:41 -0000
*************** higher_prime_number (n)
*** 125,129 ****
{
const unsigned long *mid = low + (high - low) / 2;
! if (n > *mid)
low = mid + 1;
else
--- 125,129 ----
{
const unsigned long *mid = low + (high - low) / 2;
! if (n >= *mid)
low = mid + 1;
else