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![Jeff King](/assets/img/avatar_default.png)
Long ago, in97bfeb34df
(Release pack windows before reporting out of memory., 2006-12-24), we taught xmalloc() and friends to try unmapping pack windows when malloc() failed. It's unlikely that his helps a lot in practice, and it has some downsides. First, the downsides: 1. It makes xmalloc() not thread-safe. We've worked around this in pack-objects.c, which installs its own locking version of the try_to_free_routine(). But other threaded code doesn't. 2. It makes the system as a whole harder to reason about. Functions which allocate heap memory under the hood may have farther-reaching effects than expected. That might be worth the tradeoff if there's a benefit. But in practice, it seems unlikely. We're generally dealing with mmap'd files, so the OS is going to do a much better job at responding to memory pressure by dropping individual pages (the exception is systems with NO_MMAP, but even there the OS can probably respond just as well with swapping). So the only thing we're really freeing is address space. On 64-bit systems, we have plenty of that to go around. On 32-bit systems, it could possibly help. But around the same time we made two other changes:77ccc5bbd1
(Introduce new config option for mmap limit., 2006-12-23) and60bb8b1453
(Fully activate the sliding window pack access., 2006-12-23). Together that means that a 32-bit system should have no more than 256MB total of packed-git mmaps at one time, split between a few 32MB windows. It's unlikely we have any address space problems since then, but we don't have any data since the features were all added at the same time. Likewise, xmmap() will try to free memory. At first glance, it seems like we'd need this (when we try to mmap a new window, we might need to close an old one to save address space on a 32-bit system). But we're saved again by core.packedGitLimit: if we're going to exceed our 256MB limit, we'll close an existing window before we even call mmap(). So it seems unlikely that this feature is actually doing anything useful. And while we don't have reports of it harming anything (probably because it rarely if ever kicks in), it would be nice to simplify the system overall. This patch drops the whole try_to_free system from xmalloc(), as well as the manual pack memory release in xmmap(). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
490 lines
12 KiB
C
490 lines
12 KiB
C
/*
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* GIT - The information manager from hell
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*
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* Copyright (C) 2000-2002 Michael R. Elkins <me@mutt.org>
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* Copyright (C) 2002-2004 Oswald Buddenhagen <ossi@users.sf.net>
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* Copyright (C) 2004 Theodore Y. Ts'o <tytso@mit.edu>
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* Copyright (C) 2006 Mike McCormack
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* Copyright (C) 2006 Christian Couder
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include "cache.h"
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#include "quote.h"
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struct trace_key trace_default_key = { "GIT_TRACE", 0, 0, 0 };
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struct trace_key trace_perf_key = TRACE_KEY_INIT(PERFORMANCE);
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struct trace_key trace_setup_key = TRACE_KEY_INIT(SETUP);
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/* Get a trace file descriptor from "key" env variable. */
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static int get_trace_fd(struct trace_key *key)
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{
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const char *trace;
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/* don't open twice */
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if (key->initialized)
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return key->fd;
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trace = getenv(key->key);
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if (!trace || !strcmp(trace, "") ||
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!strcmp(trace, "0") || !strcasecmp(trace, "false"))
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key->fd = 0;
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else if (!strcmp(trace, "1") || !strcasecmp(trace, "true"))
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key->fd = STDERR_FILENO;
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else if (strlen(trace) == 1 && isdigit(*trace))
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key->fd = atoi(trace);
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else if (is_absolute_path(trace)) {
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int fd = open(trace, O_WRONLY | O_APPEND | O_CREAT, 0666);
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if (fd == -1) {
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warning("could not open '%s' for tracing: %s",
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trace, strerror(errno));
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trace_disable(key);
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} else {
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key->fd = fd;
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key->need_close = 1;
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}
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} else {
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warning("unknown trace value for '%s': %s\n"
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" If you want to trace into a file, then please set %s\n"
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" to an absolute pathname (starting with /)",
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key->key, trace, key->key);
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trace_disable(key);
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}
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key->initialized = 1;
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return key->fd;
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}
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void trace_disable(struct trace_key *key)
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{
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if (key->need_close)
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close(key->fd);
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key->fd = 0;
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key->initialized = 1;
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key->need_close = 0;
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}
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static int prepare_trace_line(const char *file, int line,
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struct trace_key *key, struct strbuf *buf)
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{
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static struct trace_key trace_bare = TRACE_KEY_INIT(BARE);
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struct timeval tv;
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struct tm tm;
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time_t secs;
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if (!trace_want(key))
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return 0;
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/* unit tests may want to disable additional trace output */
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if (trace_want(&trace_bare))
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return 1;
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/* print current timestamp */
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gettimeofday(&tv, NULL);
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secs = tv.tv_sec;
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localtime_r(&secs, &tm);
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strbuf_addf(buf, "%02d:%02d:%02d.%06ld ", tm.tm_hour, tm.tm_min,
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tm.tm_sec, (long) tv.tv_usec);
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#ifdef HAVE_VARIADIC_MACROS
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/* print file:line */
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strbuf_addf(buf, "%s:%d ", file, line);
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/* align trace output (column 40 catches most files names in git) */
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while (buf->len < 40)
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strbuf_addch(buf, ' ');
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#endif
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return 1;
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}
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static void trace_write(struct trace_key *key, const void *buf, unsigned len)
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{
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if (write_in_full(get_trace_fd(key), buf, len) < 0) {
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warning("unable to write trace for %s: %s",
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key->key, strerror(errno));
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trace_disable(key);
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}
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}
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void trace_verbatim(struct trace_key *key, const void *buf, unsigned len)
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{
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if (!trace_want(key))
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return;
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trace_write(key, buf, len);
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}
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static void print_trace_line(struct trace_key *key, struct strbuf *buf)
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{
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strbuf_complete_line(buf);
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trace_write(key, buf->buf, buf->len);
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}
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static void trace_vprintf_fl(const char *file, int line, struct trace_key *key,
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const char *format, va_list ap)
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{
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struct strbuf buf = STRBUF_INIT;
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if (!prepare_trace_line(file, line, key, &buf))
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return;
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strbuf_vaddf(&buf, format, ap);
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print_trace_line(key, &buf);
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strbuf_release(&buf);
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}
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static void trace_argv_vprintf_fl(const char *file, int line,
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const char **argv, const char *format,
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va_list ap)
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{
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struct strbuf buf = STRBUF_INIT;
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if (!prepare_trace_line(file, line, &trace_default_key, &buf))
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return;
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strbuf_vaddf(&buf, format, ap);
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sq_quote_argv_pretty(&buf, argv);
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print_trace_line(&trace_default_key, &buf);
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strbuf_release(&buf);
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}
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void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
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const struct strbuf *data)
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{
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struct strbuf buf = STRBUF_INIT;
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if (!prepare_trace_line(file, line, key, &buf))
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return;
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strbuf_addbuf(&buf, data);
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print_trace_line(key, &buf);
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strbuf_release(&buf);
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}
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static uint64_t perf_start_times[10];
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static int perf_indent;
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uint64_t trace_performance_enter(void)
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{
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uint64_t now;
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if (!trace_want(&trace_perf_key))
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return 0;
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now = getnanotime();
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perf_start_times[perf_indent] = now;
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if (perf_indent + 1 < ARRAY_SIZE(perf_start_times))
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perf_indent++;
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else
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BUG("Too deep indentation");
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return now;
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}
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static void trace_performance_vprintf_fl(const char *file, int line,
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uint64_t nanos, const char *format,
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va_list ap)
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{
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static const char space[] = " ";
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struct strbuf buf = STRBUF_INIT;
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if (!prepare_trace_line(file, line, &trace_perf_key, &buf))
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return;
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strbuf_addf(&buf, "performance: %.9f s", (double) nanos / 1000000000);
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if (format && *format) {
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if (perf_indent >= strlen(space))
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BUG("Too deep indentation");
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strbuf_addf(&buf, ":%.*s ", perf_indent, space);
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strbuf_vaddf(&buf, format, ap);
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}
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print_trace_line(&trace_perf_key, &buf);
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strbuf_release(&buf);
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}
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#ifndef HAVE_VARIADIC_MACROS
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void trace_printf(const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_vprintf_fl(NULL, 0, &trace_default_key, format, ap);
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va_end(ap);
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}
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void trace_printf_key(struct trace_key *key, const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_vprintf_fl(NULL, 0, key, format, ap);
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va_end(ap);
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}
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void trace_argv_printf(const char **argv, const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_argv_vprintf_fl(NULL, 0, argv, format, ap);
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va_end(ap);
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}
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void trace_strbuf(struct trace_key *key, const struct strbuf *data)
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{
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trace_strbuf_fl(NULL, 0, key, data);
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}
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void trace_performance(uint64_t nanos, const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_performance_vprintf_fl(NULL, 0, nanos, format, ap);
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va_end(ap);
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}
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void trace_performance_since(uint64_t start, const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_performance_vprintf_fl(NULL, 0, getnanotime() - start,
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format, ap);
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va_end(ap);
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}
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void trace_performance_leave(const char *format, ...)
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{
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va_list ap;
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uint64_t since;
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if (perf_indent)
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perf_indent--;
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if (!format) /* Allow callers to leave without tracing anything */
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return;
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since = perf_start_times[perf_indent];
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va_start(ap, format);
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trace_performance_vprintf_fl(NULL, 0, getnanotime() - since,
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format, ap);
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va_end(ap);
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}
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#else
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void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
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const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_vprintf_fl(file, line, key, format, ap);
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va_end(ap);
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}
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void trace_argv_printf_fl(const char *file, int line, const char **argv,
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const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_argv_vprintf_fl(file, line, argv, format, ap);
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va_end(ap);
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}
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void trace_performance_fl(const char *file, int line, uint64_t nanos,
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const char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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trace_performance_vprintf_fl(file, line, nanos, format, ap);
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va_end(ap);
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}
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void trace_performance_leave_fl(const char *file, int line,
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uint64_t nanos, const char *format, ...)
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{
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va_list ap;
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uint64_t since;
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if (perf_indent)
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perf_indent--;
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if (!format) /* Allow callers to leave without tracing anything */
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return;
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since = perf_start_times[perf_indent];
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va_start(ap, format);
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trace_performance_vprintf_fl(file, line, nanos - since, format, ap);
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va_end(ap);
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}
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#endif /* HAVE_VARIADIC_MACROS */
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static const char *quote_crnl(const char *path)
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{
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static struct strbuf new_path = STRBUF_INIT;
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if (!path)
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return NULL;
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strbuf_reset(&new_path);
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while (*path) {
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switch (*path) {
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case '\\': strbuf_addstr(&new_path, "\\\\"); break;
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case '\n': strbuf_addstr(&new_path, "\\n"); break;
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case '\r': strbuf_addstr(&new_path, "\\r"); break;
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default:
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strbuf_addch(&new_path, *path);
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}
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path++;
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}
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return new_path.buf;
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}
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/* FIXME: move prefix to startup_info struct and get rid of this arg */
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void trace_repo_setup(const char *prefix)
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{
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const char *git_work_tree;
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char *cwd;
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if (!trace_want(&trace_setup_key))
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return;
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cwd = xgetcwd();
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if (!(git_work_tree = get_git_work_tree()))
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git_work_tree = "(null)";
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if (!prefix)
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prefix = "(null)";
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trace_printf_key(&trace_setup_key, "setup: git_dir: %s\n", quote_crnl(get_git_dir()));
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trace_printf_key(&trace_setup_key, "setup: git_common_dir: %s\n", quote_crnl(get_git_common_dir()));
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trace_printf_key(&trace_setup_key, "setup: worktree: %s\n", quote_crnl(git_work_tree));
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trace_printf_key(&trace_setup_key, "setup: cwd: %s\n", quote_crnl(cwd));
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trace_printf_key(&trace_setup_key, "setup: prefix: %s\n", quote_crnl(prefix));
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free(cwd);
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}
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int trace_want(struct trace_key *key)
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{
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return !!get_trace_fd(key);
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}
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#if defined(HAVE_CLOCK_GETTIME) && defined(HAVE_CLOCK_MONOTONIC)
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static inline uint64_t highres_nanos(void)
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{
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struct timespec ts;
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if (clock_gettime(CLOCK_MONOTONIC, &ts))
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return 0;
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return (uint64_t) ts.tv_sec * 1000000000 + ts.tv_nsec;
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}
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#elif defined (GIT_WINDOWS_NATIVE)
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static inline uint64_t highres_nanos(void)
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{
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static uint64_t high_ns, scaled_low_ns;
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static int scale;
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LARGE_INTEGER cnt;
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if (!scale) {
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if (!QueryPerformanceFrequency(&cnt))
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return 0;
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/* high_ns = number of ns per cnt.HighPart */
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high_ns = (1000000000LL << 32) / (uint64_t) cnt.QuadPart;
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/*
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* Number of ns per cnt.LowPart is 10^9 / frequency (or
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* high_ns >> 32). For maximum precision, we scale this factor
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* so that it just fits within 32 bit (i.e. won't overflow if
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* multiplied with cnt.LowPart).
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*/
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scaled_low_ns = high_ns;
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scale = 32;
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while (scaled_low_ns >= 0x100000000LL) {
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scaled_low_ns >>= 1;
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scale--;
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}
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}
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/* if QPF worked on initialization, we expect QPC to work as well */
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QueryPerformanceCounter(&cnt);
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return (high_ns * cnt.HighPart) +
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((scaled_low_ns * cnt.LowPart) >> scale);
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}
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#else
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# define highres_nanos() 0
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#endif
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static inline uint64_t gettimeofday_nanos(void)
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{
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struct timeval tv;
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gettimeofday(&tv, NULL);
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return (uint64_t) tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
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}
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/*
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* Returns nanoseconds since the epoch (01/01/1970), for performance tracing
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* (i.e. favoring high precision over wall clock time accuracy).
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*/
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uint64_t getnanotime(void)
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{
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static uint64_t offset;
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if (offset > 1) {
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/* initialization succeeded, return offset + high res time */
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return offset + highres_nanos();
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} else if (offset == 1) {
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/* initialization failed, fall back to gettimeofday */
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return gettimeofday_nanos();
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} else {
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/* initialize offset if high resolution timer works */
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uint64_t now = gettimeofday_nanos();
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uint64_t highres = highres_nanos();
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if (highres)
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offset = now - highres;
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else
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offset = 1;
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return now;
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}
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}
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static struct strbuf command_line = STRBUF_INIT;
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static void print_command_performance_atexit(void)
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{
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trace_performance_leave("git command:%s", command_line.buf);
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}
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void trace_command_performance(const char **argv)
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{
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if (!trace_want(&trace_perf_key))
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return;
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if (!command_line.len)
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atexit(print_command_performance_atexit);
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strbuf_reset(&command_line);
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sq_quote_argv_pretty(&command_line, argv);
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trace_performance_enter();
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}
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