perf: clear vfs audit_cache before each run
When generating a stream clone, we spend a large amount of time auditing path.
Before this changes, the first run was warming the vfs cache for the other
runs, leading to a large runtime difference and a "faulty" reported timing for
the operation.
We now clear this important cache between run to get a more realistic timing.
Below are some example of median time change when clearing these cases. The
maximum time for a run did not changed significantly.
### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog
# benchmark.name = hg.perf.exchange.stream.generate
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.version = latest
no-clearing: 17.289905
cache-clearing: 21.587965 (+24.86%, +4.30)
## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog
no-clearing: 32.670748
cache-clearing: 40.467095 (+23.86%, +7.80)
## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog
no-clearing: 37.838858
cache-clearing: 46.072749 (+21.76%, +8.23)
## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog
no-clearing: 32.969395
cache-clearing: 39.646209 (+20.25%, +6.68)
In addition, this significantly reduce the timing difference between the
performance command, from the perf extensions and a `real `hg bundle` call
producing a stream bundle. Some significant differences remain especially on
the "mozilla-try" repositories, but they are now smaller.
Note that some of that difference will actually not be
attributable to the stream generation (like maybe phases or branch map
computation).
Below are some benchmarks done on a currently draft changeset fixing some
unrelated slowness in `hg bundle` (34a78972af409d1ff37c29e60f6ca811ad1a457d)
### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
hg.perf.exchange.stream.generate: 21.587965
hg.command.bundle: 24.301799 (+12.57%, +2.71)
## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 40.467095
hg.command.bundle: 44.831317 (+10.78%, +4.36)
## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 39.646209
hg.command.bundle: 45.395258 (+14.50%, +5.75)
## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 46.072749
hg.command.bundle: 55.882608 (+21.29%, +9.81)
## data-env-vars.name = mozilla-try-2023-03-22-zlib-general-delta
hg.perf.exchange.stream.generate: 334.716708
hg.command.bundle: 377.856767 (+12.89%, +43.14)
## data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 302.972301
hg.command.bundle: 326.098755 (+7.63%, +23.13)
/*
mpatch.c - efficient binary patching for Mercurial
This implements a patch algorithm that's O(m + nlog n) where m is the
size of the output and n is the number of patches.
Given a list of binary patches, it unpacks each into a hunk list,
then combines the hunk lists with a treewise recursion to form a
single hunk list. This hunk list is then applied to the original
text.
The text (or binary) fragments are copied directly from their source
Python objects into a preallocated output string to avoid the
allocation of intermediate Python objects. Working memory is about 2x
the total number of hunks.
Copyright 2005, 2006 Olivia Mackall <olivia@selenic.com>
This software may be used and distributed according to the terms
of the GNU General Public License, incorporated herein by reference.
*/
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "bitmanipulation.h"
#include "compat.h"
#include "mpatch.h"
/* VC9 doesn't include bool and lacks stdbool.h based on cext/util.h */
#if defined(_MSC_VER) || __STDC_VERSION__ < 199901L
#define true 1
#define false 0
typedef unsigned char bool;
#else
#include <stdbool.h>
#endif
static struct mpatch_flist *lalloc(ssize_t size)
{
struct mpatch_flist *a = NULL;
if (size < 1) {
size = 1;
}
a = (struct mpatch_flist *)malloc(sizeof(struct mpatch_flist));
if (a) {
a->base = (struct mpatch_frag *)malloc(
sizeof(struct mpatch_frag) * size);
if (a->base) {
a->head = a->tail = a->base;
return a;
}
free(a);
}
return NULL;
}
void mpatch_lfree(struct mpatch_flist *a)
{
if (a) {
free(a->base);
free(a);
}
}
static ssize_t lsize(struct mpatch_flist *a)
{
return a->tail - a->head;
}
/* add helper to add src and *dest iff it won't overflow */
static inline bool safeadd(int src, int *dest)
{
if ((src > 0) == (*dest > 0)) {
if (*dest > 0) {
if (src > (INT_MAX - *dest)) {
return false;
}
} else {
if (src < (INT_MIN - *dest)) {
return false;
}
}
}
*dest += src;
return true;
}
/* subtract src from dest and store result in dest */
static inline bool safesub(int src, int *dest)
{
if (((src > 0) && (*dest < INT_MIN + src)) ||
((src < 0) && (*dest > INT_MAX + src))) {
return false;
}
*dest -= src;
return true;
}
/* move hunks in source that are less cut to dest, compensating
for changes in offset. the last hunk may be split if necessary.
*/
static int gather(struct mpatch_flist *dest, struct mpatch_flist *src, int cut,
int offset)
{
struct mpatch_frag *d = dest->tail, *s = src->head;
int postend, c, l;
while (s != src->tail) {
int soffset = s->start;
if (!safeadd(offset, &soffset)) {
break; /* add would overflow, oh well */
}
if (soffset >= cut) {
break; /* we've gone far enough */
}
postend = offset;
if (!safeadd(s->start, &postend) ||
!safeadd(s->len, &postend)) {
break;
}
if (postend <= cut) {
/* save this hunk */
int tmp = s->start;
if (!safesub(s->end, &tmp)) {
break;
}
if (!safeadd(s->len, &tmp)) {
break;
}
if (!safeadd(tmp, &offset)) {
break; /* add would overflow, oh well */
}
*d++ = *s++;
} else {
/* break up this hunk */
c = cut;
if (!safesub(offset, &c)) {
break;
}
if (s->end < c) {
c = s->end;
}
l = cut - offset - s->start;
if (s->len < l) {
l = s->len;
}
offset += s->start + l - c;
d->start = s->start;
d->end = c;
d->len = l;
d->data = s->data;
d++;
s->start = c;
s->len = s->len - l;
s->data = s->data + l;
break;
}
}
dest->tail = d;
src->head = s;
return offset;
}
/* like gather, but with no output list */
static int discard(struct mpatch_flist *src, int cut, int offset)
{
struct mpatch_frag *s = src->head;
int postend, c, l;
while (s != src->tail) {
int cmpcut = s->start;
if (!safeadd(offset, &cmpcut)) {
break;
}
if (cmpcut >= cut) {
break;
}
postend = offset;
if (!safeadd(s->start, &postend)) {
break;
}
if (!safeadd(s->len, &postend)) {
break;
}
if (postend <= cut) {
/* do the subtraction first to avoid UB integer overflow
*/
int tmp = s->start;
if (!safesub(s->end, &tmp)) {
break;
}
if (!safeadd(s->len, &tmp)) {
break;
}
if (!safeadd(tmp, &offset)) {
break;
}
s++;
} else {
c = cut;
if (!safesub(offset, &c)) {
break;
}
if (s->end < c) {
c = s->end;
}
l = cut - offset - s->start;
if (s->len < l) {
l = s->len;
}
offset += s->start + l - c;
s->start = c;
s->len = s->len - l;
s->data = s->data + l;
break;
}
}
src->head = s;
return offset;
}
/* combine hunk lists a and b, while adjusting b for offset changes in a/
this deletes a and b and returns the resultant list. */
static struct mpatch_flist *combine(struct mpatch_flist *a,
struct mpatch_flist *b)
{
struct mpatch_flist *c = NULL;
struct mpatch_frag *bh, *ct;
int offset = 0, post;
if (a && b) {
c = lalloc((lsize(a) + lsize(b)) * 2);
}
if (c) {
for (bh = b->head; bh != b->tail; bh++) {
/* save old hunks */
offset = gather(c, a, bh->start, offset);
/* discard replaced hunks */
post = discard(a, bh->end, offset);
/* insert new hunk */
ct = c->tail;
ct->start = bh->start;
ct->end = bh->end;
if (!safesub(offset, &(ct->start)) ||
!safesub(post, &(ct->end))) {
/* It was already possible to exit
* this function with a return value
* of NULL before the safesub()s were
* added, so this should be fine. */
mpatch_lfree(c);
c = NULL;
goto done;
}
ct->len = bh->len;
ct->data = bh->data;
c->tail++;
offset = post;
}
/* hold on to tail from a */
memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a));
c->tail += lsize(a);
}
done:
mpatch_lfree(a);
mpatch_lfree(b);
return c;
}
/* decode a binary patch into a hunk list */
int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res)
{
struct mpatch_flist *l;
struct mpatch_frag *lt;
int pos = 0;
/* assume worst case size, we won't have many of these lists */
l = lalloc(len / 12 + 1);
if (!l) {
return MPATCH_ERR_NO_MEM;
}
lt = l->tail;
/* We check against len-11 to ensure we have at least 12 bytes
left in the patch so we can read our three be32s out of it. */
while (pos >= 0 && pos < (len - 11)) {
lt->start = getbe32(bin + pos);
lt->end = getbe32(bin + pos + 4);
lt->len = getbe32(bin + pos + 8);
if (lt->start < 0 || lt->start > lt->end || lt->len < 0) {
break; /* sanity check */
}
if (!safeadd(12, &pos)) {
break;
}
lt->data = bin + pos;
if (!safeadd(lt->len, &pos)) {
break;
}
lt++;
}
if (pos != len) {
mpatch_lfree(l);
return MPATCH_ERR_CANNOT_BE_DECODED;
}
l->tail = lt;
*res = l;
return 0;
}
/* calculate the size of resultant text */
ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l)
{
ssize_t outlen = 0, last = 0;
struct mpatch_frag *f = l->head;
while (f != l->tail) {
if (f->start < last || f->end > len) {
return MPATCH_ERR_INVALID_PATCH;
}
outlen += f->start - last;
last = f->end;
outlen += f->len;
f++;
}
outlen += len - last;
return outlen;
}
int mpatch_apply(char *buf, const char *orig, ssize_t len,
struct mpatch_flist *l)
{
struct mpatch_frag *f = l->head;
int last = 0;
char *p = buf;
while (f != l->tail) {
if (f->start < last || f->start > len || f->end > len ||
last < 0) {
return MPATCH_ERR_INVALID_PATCH;
}
memcpy(p, orig + last, f->start - last);
p += f->start - last;
memcpy(p, f->data, f->len);
last = f->end;
p += f->len;
f++;
}
if (last < 0) {
return MPATCH_ERR_INVALID_PATCH;
}
memcpy(p, orig + last, len - last);
return 0;
}
/* recursively generate a patch of all bins between start and end */
struct mpatch_flist *
mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t),
ssize_t start, ssize_t end)
{
ssize_t len;
if (start + 1 == end) {
/* trivial case, output a decoded list */
return get_next_item(bins, start);
}
/* divide and conquer, memory management is elsewhere */
len = (end - start) / 2;
return combine(mpatch_fold(bins, get_next_item, start, start + len),
mpatch_fold(bins, get_next_item, start + len, end));
}