Commit 5772498e authored by Stefan Fritsch's avatar Stefan Fritsch
Browse files

Optimize memory access pattern of ap_merge_per_dir_configs() 

According to Linux perf, this is twice as fast as the old loop.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1066869 13f79535-47bb-0310-9956-ffa450edef68
parent 8d2254ab

server/config.c

+18 −7
Changes for server/config.c: 18 added lines, 7 removed lines.
Original line number Diff line number Diff line
@@ -210,6 +210,14 @@ typedef int (*handler_func)(request_rec *); 
typedef void *(*dir_maker_func)(apr_pool_t *, char *);

typedef void *(*merger_func)(apr_pool_t *, void *, void *);



/* A list of the merge_dir_config functions of all loaded modules, sorted

 * by module_index.

 * Using this list in ap_merge_per_dir_configs() is faster than following

 * the module->next linked list because of better memory locality (resulting

 * in better cache usage).

 */

static merger_func *merger_func_cache;



/* maximum nesting level for config directories */

#ifndef AP_MAX_INCLUDE_DIR_DEPTH

#define AP_MAX_INCLUDE_DIR_DEPTH (128)
@@ -254,16 +262,14 @@ AP_CORE_DECLARE(ap_conf_vector_t *) ap_merge_per_dir_configs(apr_pool_t *p, 
    void **conf_vector = apr_palloc(p, sizeof(void *) * conf_vector_length);

    void **base_vector = (void **)base;

    void **new_vector = (void **)new_conf;

    module *modp;



    for (modp = ap_top_module; modp; modp = modp->next) {

        int i = modp->module_index;

    int i;



    for (i = 0; i < total_modules; i++) {

        if (!new_vector[i]) {

            conf_vector[i] = base_vector[i];

        }

        else {

            merger_func df = modp->merge_dir_config;

            const merger_func df = merger_func_cache[i];

            if (df && base_vector[i]) {

                conf_vector[i] = (*df)(p, base_vector[i], new_vector[i]);

            }
@@ -571,6 +577,7 @@ AP_DECLARE(const char *) ap_add_module(module *m, apr_pool_t *p, 


        ap_module_short_names[m->module_index] = strdup(sym_name);

        ap_module_short_names[m->module_index][len] = '\0';

        merger_func_cache[m->module_index] = m->merge_dir_config;

    }
@@ -648,6 +655,7 @@ AP_DECLARE(void) ap_remove_module(module *m) 


    free(ap_module_short_names[m->module_index]);

    ap_module_short_names[m->module_index] = NULL;

    merger_func_cache[m->module_index] = NULL;



    m->module_index = -1; /* simulate being unloaded, should

                           * be unnecessary */
@@ -743,9 +751,12 @@ AP_DECLARE(const char *) ap_setup_prelinked_modules(process_rec *process) 
    if (!ap_module_short_names)

        ap_module_short_names = calloc(sizeof(char *), conf_vector_length);



    if (ap_loaded_modules == NULL || ap_module_short_names == NULL) {

    if (!merger_func_cache)

        merger_func_cache = calloc(sizeof(merger_func), conf_vector_length);



    if (ap_loaded_modules == NULL || ap_module_short_names == NULL

        || merger_func_cache == NULL)

        return "Ouch! Out of memory in ap_setup_prelinked_modules()!";

    }



    for (m = ap_preloaded_modules, m2 = ap_loaded_modules; *m != NULL; )

        *m2++ = *m++;