[Opensrf-commits] r1888 - trunk/src/libopensrf (scottmk)
svn at svn.open-ils.org
svn at svn.open-ils.org
Sat Jan 9 15:55:02 EST 2010
Author: scottmk
Date: 2010-01-09 15:54:57 -0500 (Sat, 09 Jan 2010)
New Revision: 1888
Modified:
trunk/src/libopensrf/osrf_prefork.c
Log:
1. For keeping track of the child processes: use a doubly-linked
list instead of a singly-linked list. The resulting list manipulations
are both simpler (fewer special cases) and faster (no need to traverse
then entire list just to find the end).
2. Maintain a free list of prefork_child structures that have been
allocated but are not currently in use. Allocate from the free list
when possible, in order to avoid churning through malloc() and free().
3. When initializing prefork_child.appname: assign it the same value
as the corresponding field in the parental prefork_simple, instead of
creating a separate copy. The parental copy will remain valid until
after all the prefork_children are gone.
M src/libopensrf/osrf_prefork.c
Modified: trunk/src/libopensrf/osrf_prefork.c
===================================================================
--- trunk/src/libopensrf/osrf_prefork.c 2010-01-09 20:23:05 UTC (rev 1887)
+++ trunk/src/libopensrf/osrf_prefork.c 2010-01-09 20:54:57 UTC (rev 1888)
@@ -9,7 +9,7 @@
child dies, either deliberately or otherwise, we can spawn another one to replace it,
keeping the number of children within a predefined range.
- Use a singly-linked circular list to keep track of the children, forwarding requests to them
+ Use a doubly-linked circular list to keep track of the children, forwarding requests to them
in an approximately round-robin fashion.
For each child, set up two pipes:
@@ -51,9 +51,13 @@
int data_to_parent; /**< Unused. */
int current_num_children; /**< How many children are currently on the list. */
int keepalive; /**< Keepalive time for stateful sessions. */
- char* appname; /**< Name of the application.
+ char* appname; /**< Name of the application. */
/** Points to a circular linked list of children */
struct prefork_child_struct* first_child;
+ /** List of allocated but unused prefork_children, available for reuse. Each one is just
+ raw memory, apart from the "next" pointer used to stitch them together. In particular,
+ there is no child process for them, and the file descriptors are not open. */
+ struct prefork_child_struct* free_list;
transport_client* connection; /**< Connection to Jabber */
} prefork_simple;
@@ -65,9 +69,10 @@
int write_status_fd; /**< Child uses to notify parent when it's available again */
int available; /**< Boolean; true when the child is between requests */
int max_requests; /**< How many requests a child can process before terminating */
- char* appname; /**< Name of the application */
+ const char* appname; /**< Name of the application */
int keepalive; /**< Keepalive time for stateful sessions. */
struct prefork_child_struct* next; /**< Linkage pointer for linked list */
+ struct prefork_child_struct* prev; /**< Linkage pointer for linked list */
};
typedef struct prefork_child_struct prefork_child;
@@ -83,14 +88,14 @@
static void check_children( prefork_simple* forker, int forever );
static void prefork_child_process_request(prefork_child*, char* data);
static int prefork_child_init_hook(prefork_child*);
-static prefork_child* prefork_child_init(
- int max_requests, int read_data_fd, int write_data_fd,
+static prefork_child* prefork_child_init( prefork_simple* forker,
+ int read_data_fd, int write_data_fd,
int read_status_fd, int write_status_fd );
/* listens on the 'data_to_child' fd and wait for incoming data */
static void prefork_child_wait( prefork_child* child );
static void prefork_clear( prefork_simple* );
-static void prefork_child_free( prefork_child* );
+static void prefork_child_free( prefork_simple* forker, prefork_child* );
static void osrf_prefork_register_routers( const char* appname );
static void osrf_prefork_child_exit( prefork_child* );
@@ -406,6 +411,7 @@
prefork->keepalive = 0;
prefork->appname = NULL;
prefork->first_child = NULL;
+ prefork->free_list = NULL;
prefork->connection = client;
return 0;
@@ -430,13 +436,9 @@
osrfLogInternal( OSRF_LOG_MARK, "Pipes: %d %d %d %d",
data_fd[0], data_fd[1], status_fd[0], status_fd[1] );
- prefork_child* child = prefork_child_init( forker->max_requests, data_fd[0],
+ prefork_child* child = prefork_child_init( forker, data_fd[0],
data_fd[1], status_fd[0], status_fd[1] );
- child->appname = strdup(forker->appname);
- child->keepalive = forker->keepalive;
-
-
add_prefork_child( forker, child );
if( (pid=fork()) < 0 ) {
@@ -791,7 +793,7 @@
}
/**
- @brief Add a prefork_child to the list.
+ @brief Add a prefork_child to the end of the list.
@param forker Pointer to the prefork_simple that owns the list.
@param child Pointer to the prefork_child to be added.
*/
@@ -801,24 +803,17 @@
// Simplest case: list is initially empty.
forker->first_child = child;
child->next = child;
- return;
- }
+ child->prev = child;
+ } else {
+ // Find the last node in the circular list.
+ prefork_child* last_child = forker->first_child->prev;
- // Reposition forker->first_child to the last node by walking around the circle.
- prefork_child* start_child = forker->first_child;
- while(1) {
- if( forker->first_child->next == start_child )
- break;
- forker->first_child = forker->first_child->next;
+ // Insert the new child between the last and first children.
+ last_child->next = child;
+ child->prev = last_child;
+ child->next = forker->first_child;
+ forker->first_child->prev = child;
}
-
- // Insert the new child after forker->first_child.
- forker->first_child->next = child;
- child->next = start_child;
- return;
-
- // What had been the last node in the list is now the first node,
- // and the new node is second.
}
/**
@@ -830,57 +825,39 @@
*/
static void del_prefork_child( prefork_simple* forker, pid_t pid ) {
- if( forker->first_child == NULL ) { return; }
+ if( forker->first_child == NULL )
+ return; // Empty list; bail out.
- (forker->current_num_children)--;
osrfLogDebug( OSRF_LOG_MARK, "Deleting Child: %d", pid );
- prefork_child* start_child = forker->first_child; /* starting point */
- prefork_child* cur_child = start_child; /* current pointer */
- prefork_child* prev_child = start_child; /* the trailing pointer */
-
- /* special case where there is only one in the list */
- if( start_child == start_child->next ) {
- if( start_child->pid == pid ) {
- forker->first_child = NULL;
- prefork_child_free( start_child );
- }
- return;
- }
-
-
- /* special case where the first item in the list needs to be removed */
- if( start_child->pid == pid ) {
-
- /* find the last one so we can remove the start_child */
- do {
- prev_child = cur_child;
- cur_child = cur_child->next;
- } while( cur_child != start_child );
-
- /* now cur_child == start_child */
- prev_child->next = cur_child->next;
- forker->first_child = prev_child;
- prefork_child_free( cur_child );
- return;
- }
-
- do {
- prev_child = cur_child;
+ // Find the node in question
+ prefork_child* cur_child = forker->first_child; /* current pointer */
+ while( cur_child->pid != pid && cur_child->next != forker->first_child )
cur_child = cur_child->next;
- if( cur_child->pid == pid ) {
- prev_child->next = cur_child->next;
- prefork_child_free( cur_child );
- return;
+ if( cur_child->pid == pid ) {
+ // We found the right node. Remove it from the list.
+ if( cur_child->next == cur_child )
+ forker->first_child = NULL; // only child in the list
+ else {
+ if( forker->first_child == cur_child )
+ forker->first_child = cur_child->next; // Reseat forker->first_child
+
+ // Stitch the nodes on either side together
+ cur_child->prev->next = cur_child->next;
+ cur_child->next->prev = cur_child->prev;
}
-
- } while(cur_child != start_child);
+ --forker->current_num_children;
+
+ //Destroy the node
+ prefork_child_free( forker, cur_child );
+
+ } // else we didn't find a matching node; bail out
}
/**
@brief Create and initialize a prefork_child.
- @param max_requests How many requests to service before terminating.
+ @param forker Pointer to the prefork_simple that will own the prefork_child.
@param read_data_fd Used by child to read request from parent.
@param write_data_fd Used by parent to write request to child.
@param read_status_fd Used by parent to read status from child.
@@ -890,21 +867,30 @@
The calling code is responsible for freeing the prefork_child by calling
prefork_child_free().
*/
-static prefork_child* prefork_child_init(
- int max_requests, int read_data_fd, int write_data_fd,
+static prefork_child* prefork_child_init( prefork_simple* forker,
+ int read_data_fd, int write_data_fd,
int read_status_fd, int write_status_fd ) {
- prefork_child* child = (prefork_child*) safe_malloc(sizeof(prefork_child));
+ // Allocate a prefork_child -- from the free list if possible, or from
+ // the heap if necessary. The free list is a non-circular, singly-linked list.
+ prefork_child* child;
+ if( forker->free_list ) {
+ child = forker->free_list;
+ forker->free_list = child->next;
+ } else
+ child = (prefork_child*) safe_malloc(sizeof(prefork_child));
+
child->pid = 0;
- child->max_requests = max_requests;
child->read_data_fd = read_data_fd;
child->write_data_fd = write_data_fd;
child->read_status_fd = read_status_fd;
child->write_status_fd = write_status_fd;
child->available = 1;
- child->appname = NULL;
- child->keepalive = 0;
+ child->max_requests = forker->max_requests;
+ child->appname = forker->appname; // We don't make a separate copy
+ child->keepalive = forker->keepalive;
child->next = NULL;
+ child->prev = NULL;
return child;
}
@@ -920,7 +906,7 @@
// Kill all the child processes with a single call, not by killing each one separately.
// Implication: we can't have more than one prefork_simple outstanding, because
- // destroying one would kill the children of both.
+ // destroying one would kill the children of all.
while( prefork->first_child != NULL ) {
osrfLogInfo( OSRF_LOG_MARK, "Killing child processes ..." );
kill( 0, SIGKILL );
@@ -933,19 +919,34 @@
while( (child_pid = waitpid(-1, NULL, WNOHANG)) > 0)
del_prefork_child( prefork, child_pid );
- client_free(prefork->connection); // Close the Jabber connection
+ // Close the Jabber connection
+ client_free(prefork->connection);
+
+ // Physically free the free list of prefork_children.
+ prefork_child* child = prefork->first_child;
+ while( child ) {
+ prefork_child* temp = child->next;
+ free( child );
+ child = temp;
+ }
+
free(prefork->appname);
}
/**
@brief Destroy and deallocate a prefork_child.
+ @param forker Pointer to the prefork_simple that owns the prefork_child.
@param child Pointer to the prefork_child to be destroyed.
*/
-static void prefork_child_free( prefork_child* child ) {
- free(child->appname);
+static void prefork_child_free( prefork_simple* forker, prefork_child* child ) {
close( child->read_data_fd );
close( child->write_data_fd );
close( child->read_status_fd );
close( child->write_status_fd );
- free( child );
+
+ // Stick the prefork_child in a free list for potential reuse. This is a
+ // non-circular, singly linked list.
+ child->prev = NULL;
+ child->next = forker->free_list;
+ forker->free_list = child;
}
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