From: Justin Erenkrantz Date: Wed, 19 Sep 2001 06:53:26 +0000 (+0000) Subject: The call to apr_explode_localtime() in mod_log_config is one of the more X-Git-Tag: 2.0.26~218 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=867166bede959c9ba2d18a66d72e4a442fdb0102;p=thirdparty%2Fapache%2Fhttpd.git The call to apr_explode_localtime() in mod_log_config is one of the more expensive operations in the httpd. This patch attempts to reduce the overhead by caching the result for 15 seconds. Submitted by: Brian Pane Reviewed by: Cliff Woolley, Ryan Bloom, Dean Gaudet, Justin Erenkrantz git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91083 13f79535-47bb-0310-9956-ffa450edef68 --- diff --git a/CHANGES b/CHANGES index 4089a46f794..d915380d541 100644 --- a/CHANGES +++ b/CHANGES @@ -1,5 +1,8 @@ Changes with Apache 2.0.26-dev + *) Cache apr_explode_localtime() value for 15 seconds. + [Brian Pane ] + *) Fix mod_include to not return ETag or Last-Modified headers. [Ian Holsman ] diff --git a/include/util_time.h b/include/util_time.h new file mode 100644 index 00000000000..704d0e02d55 --- /dev/null +++ b/include/util_time.h @@ -0,0 +1,111 @@ +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2001 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, + * if any, must include the following acknowledgment: + * "This product includes software developed by the + * Apache Software Foundation (http://www.apache.org/)." + * Alternately, this acknowledgment may appear in the software itself, + * if and wherever such third-party acknowledgments normally appear. + * + * 4. The names "Apache" and "Apache Software Foundation" must + * not be used to endorse or promote products derived from this + * software without prior written permission. For written + * permission, please contact apache@apache.org. + * + * 5. Products derived from this software may not be called "Apache", + * nor may "Apache" appear in their name, without prior written + * permission of the Apache Software Foundation. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * . + * + */ + +#ifndef APACHE_UTIL_TIME_H +#define APACHE_UTIL_TIME_H + +#include "apr.h" +#include "apr_time.h" +#include "httpd.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/** + * @package Apache date/time handling functions + */ + +/* Maximum delta from the current time, in seconds, for a past time + * to qualify as "recent" for use in the ap_explode_recent_*() functions: + */ +#define AP_TIME_RECENT_THRESHOLD 15 + +/** + * convert a recent time to its human readable components in local timezone + * @param tm the exploded time + * @param t the time to explode: MUST be within the last + * AP_TIME_RECENT_THRESHOLD seconds + * @note This is a faster alternative to apr_explode_localtime that uses + * a cache of pre-exploded time structures. It is useful for things + * that need to explode the current time multiple times per second, + * like loggers. + * @return APR_SUCCESS iff successful + * @deffunc apr_status_t ap_explode_recent_localtime(apr_exploded_time_t *tm, apr_time_t t); + */ +AP_DECLARE(apr_status_t) ap_explode_recent_localtime(apr_exploded_time_t *tm, + apr_time_t t); + +/** + * convert a recent time to its human readable components in GMT timezone + * @param tm the exploded time + * @param t the time to explode: MUST be within the last + * AP_TIME_RECENT_THRESHOLD seconds + * @note This is a faster alternative to apr_explode_gmt that uses + * a cache of pre-exploded time structures. It is useful for things + * that need to explode the current time multiple times per second, + * like loggers. + * @return APR_SUCCESS iff successful + * @deffunc apr_status_t ap_explode_recent_gmt(apr_exploded_time_t *tm, apr_time_t t); + */ +AP_DECLARE(apr_status_t) ap_explode_recent_gmt(apr_exploded_time_t *tm, + apr_time_t t); + + +#ifdef __cplusplus +} +#endif + +#endif /* !APACHE_UTIL_TIME_H */ diff --git a/modules/loggers/mod_log_config.c b/modules/loggers/mod_log_config.c index e6f2a713a4d..95ff9d7ad78 100644 --- a/modules/loggers/mod_log_config.c +++ b/modules/loggers/mod_log_config.c @@ -196,6 +196,7 @@ #include "http_core.h" /* For REMOTE_NAME */ #include "http_log.h" #include "http_protocol.h" +#include "util_time.h" #if APR_HAVE_UNISTD_H #include @@ -463,9 +464,9 @@ static const char *log_request_time(request_rec *r, char *a) a problem with this, you can set the define. -djg */ #ifdef I_INSIST_ON_EXTRA_CYCLES_FOR_CLF_COMPLIANCE - apr_explode_localtime(&xt, apr_time_now()); + ap_explode_recent_localtime(&xt, apr_time_now()); #else - apr_explode_localtime(&xt, r->request_time); + ap_explode_recent_localtime(&xt, r->request_time); #endif if (a && *a) { /* Custom format */ apr_strftime(tstr, &retcode, MAX_STRING_LEN, a, &xt); diff --git a/server/Makefile.in b/server/Makefile.in index bc872a35f42..556a5a4e2f6 100644 --- a/server/Makefile.in +++ b/server/Makefile.in @@ -11,10 +11,10 @@ LTLIBRARY_NAME = libmain.la LTLIBRARY_SOURCES = \ test_char.h \ config.c log.c main.c vhost.c util.c \ - util_script.c util_md5.c util_cfgtree.c util_ebcdic.c \ + util_script.c util_md5.c util_cfgtree.c util_ebcdic.c util_time.c \ rfc1413.c connection.c listen.c \ - mpm_common.c util_charset.c util_debug.c util_xml.c \ - util_filter.c exports.c buildmark.c scoreboard.c \ + mpm_common.c util_charset.c util_debug.c util_xml.c \ + util_filter.c exports.c buildmark.c scoreboard.c \ error_bucket.c protocol.c core.c request.c TARGETS = delete-exports $(LTLIBRARY_NAME) $(CORE_IMPLIB_FILE) export_vars.h httpd.exp diff --git a/server/util_time.c b/server/util_time.c new file mode 100644 index 00000000000..3db076bceab --- /dev/null +++ b/server/util_time.c @@ -0,0 +1,175 @@ +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2001 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, + * if any, must include the following acknowledgment: + * "This product includes software developed by the + * Apache Software Foundation (http://www.apache.org/)." + * Alternately, this acknowledgment may appear in the software itself, + * if and wherever such third-party acknowledgments normally appear. + * + * 4. The names "Apache" and "Apache Software Foundation" must + * not be used to endorse or promote products derived from this + * software without prior written permission. For written + * permission, please contact apache@apache.org. + * + * 5. Products derived from this software may not be called "Apache", + * nor may "Apache" appear in their name, without prior written + * permission of the Apache Software Foundation. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * . + * + */ + +#include "util_time.h" + +/* Cache for exploded values of recent timestamps + */ + +struct exploded_time_cache_element { + apr_int64_t t; + apr_exploded_time_t xt; + apr_int64_t t_validate; /* please see comments in cached_explode() */ +}; + +/* the "+ 1" is for the current second: */ +#define TIME_CACHE_SIZE (AP_TIME_RECENT_THRESHOLD + 1) + +static struct exploded_time_cache_element exploded_cache_localtime[TIME_CACHE_SIZE]; +static struct exploded_time_cache_element exploded_cache_gmt[TIME_CACHE_SIZE]; + + +static apr_status_t cached_explode(apr_exploded_time_t *xt, apr_time_t t, + struct exploded_time_cache_element *cache, + int use_gmt) +{ + apr_int64_t seconds = t / APR_USEC_PER_SEC; + struct exploded_time_cache_element *cache_element = + &(cache[seconds % TIME_CACHE_SIZE]); + struct exploded_time_cache_element cache_element_snapshot; + + /* The cache is implemented as a ring buffer. Each second, + * it uses a different element in the buffer. The timestamp + * in the element indicates whether the element contains the + * exploded time for the current second (vs the time + * 'now - AP_TIME_RECENT_THRESHOLD' seconds ago). If the + * cached value is for the current time, we use it. Otherwise, + * we compute the apr_exploded_time_t and store it in this + * cache element. Note that the timestamp in the cache + * element is updated only after the exploded time. Thus + * if two threads hit this cache element simultaneously + * at the start of a new second, they'll both explode the + * time and store it. I.e., the writers will collide, but + * they'll be writing the same value. + */ + if (cache_element->t >= seconds) { + /* There is an intentional race condition in this design: + * in a multithreaded app, one thread might be reading + * from this cache_element to resolve a timestamp from + * TIME_CACHE_SIZE seconds ago at the same time that + * another thread is copying the exploded form of the + * current time into the same cache_element. (I.e., the + * first thread might hit this element of the ring buffer + * just as the element is being recycled.) This can + * also happen at the start of a new second, if a + * reader accesses the cache_element after a writer + * has updated cache_element.t but before the writer + * has finished updating the whole cache_element. + * + * Rather than trying to prevent this race condition + * with locks, we allow it to happen and then detect + * and correct it. The detection works like this: + * Step 1: Take a "snapshot" of the cache element by + * copying it into a temporary buffer. + * Step 2: Check whether the snapshot contains consistent + * data: the timestamps at the start and end of + * the cache_element should both match the 'seconds' + * value that we computed from the input time. + * If these three don't match, then the snapshot + * shows the cache_element in the middle of an + * update, and its contents are invalid. + * Step 3: If the snapshot is valid, use it. Otherwise, + * just give up on the cache and explode the + * input time. + */ + memcpy(&cache_element_snapshot, cache_element, + sizeof(struct exploded_time_cache_element)); + if ((seconds != cache_element_snapshot.t) || + (seconds != cache_element_snapshot.t_validate)) { + /* Invalid snapshot */ + if (use_gmt) { + return apr_explode_gmt(xt, t); + } + else { + return apr_explode_localtime(xt, t); + } + } + else { + /* Valid snapshot */ + memcpy(xt, &(cache_element_snapshot.xt), + sizeof(apr_exploded_time_t)); + } + } + else { + apr_status_t r; + if (use_gmt) { + r = apr_explode_gmt(xt, t); + } + else { + r = apr_explode_localtime(xt, t); + } + if (!APR_STATUS_IS_SUCCESS(r)) { + return r; + } + cache_element->t = seconds; + memcpy(&(cache_element->xt), xt, sizeof(apr_exploded_time_t)); + cache_element->t_validate = seconds; + } + xt->tm_usec = t % APR_USEC_PER_SEC; + return APR_SUCCESS; +} + + +AP_DECLARE(apr_status_t) ap_explode_recent_localtime(apr_exploded_time_t * tm, + apr_time_t t) +{ + return cached_explode(tm, t, exploded_cache_localtime, 0); +} + +AP_DECLARE(apr_status_t) ap_explode_recent_gmt(apr_exploded_time_t * tm, + apr_time_t t) +{ + return cached_explode(tm, t, exploded_cache_gmt, 1); +}