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Zap the rotor, it was a wrong idea. Cluebat applied by kshe who

came also up with this diff. Simple, no bias and benchmarks show the extra
random calls disappear in te measurement noise.
OPENBSD_6_3
otto 6 years ago
parent
commit
d471572632
1 changed files with 3 additions and 6 deletions
  1. +3
    -6
      src/lib/libc/stdlib/malloc.c

+ 3
- 6
src/lib/libc/stdlib/malloc.c View File

@ -1,4 +1,4 @@
/* $OpenBSD: malloc.c,v 1.240 2018/01/18 08:37:28 otto Exp $ */
/* $OpenBSD: malloc.c,v 1.241 2018/01/18 20:06:16 otto Exp $ */
/*
* Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
* Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@ -172,7 +172,6 @@ struct chunk_info {
u_short free; /* how many free chunks */
u_short total; /* how many chunks */
u_short offset; /* requested size table offset */
u_short rotor; /* randomization rotor */
u_short bits[1]; /* which chunks are free */
};
@ -941,7 +940,7 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
j = find_chunksize(size);
r = getrbyte(d);
r = ((u_int)getrbyte(d) << 8) | getrbyte(d);
listnum = r % MALLOC_CHUNK_LISTS;
/* If it's empty, make a page more of that size chunks */
if ((bp = LIST_FIRST(&d->chunk_dir[j][listnum])) == NULL) {
@ -953,9 +952,7 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
if (bp->canary != (u_short)d->canary1)
wrterror(d, "chunk info corrupted");
if (bp->free > 1)
bp->rotor += r;
i = bp->rotor++ & (bp->total - 1);
i = (r / MALLOC_CHUNK_LISTS) & (bp->total - 1);
/* start somewhere in a short */
lp = &bp->bits[i / MALLOC_BITS];


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