introduce a generic priority queue implementation

src/Makefile.am

@@ -53,8 +53,8 @@ mandatory_sources = colours.c colours.h combine.c combine.h common.c common.h \
 		conky.cc conky.h core.cc core.h diskio.c diskio.h entropy.c entropy.h \
 		exec.c exec.h fs.c fs.h logging.h mail.c mail.h mixer.c mixer.h net_stat.c \
 		net_stat.h template.c template.h timed_thread.c timed_thread.h mboxscan.c \
-		mboxscan.h read_tcp.c read_tcp.h scroll.c scroll.h specials.c \
-		specials.h tailhead.c tailhead.h temphelper.c temphelper.h \
+		mboxscan.h prioqueue.c prioqueue.h read_tcp.c read_tcp.h scroll.c scroll.h \
+		specials.c specials.h tailhead.c tailhead.h temphelper.c temphelper.h \
 		text_object.c text_object.h timeinfo.c timeinfo.h top.c top.h algebra.c \
 		algebra.h proc.c proc.h user.c user.h
 

src/prioqueue.c

@@ -0,0 +1,207 @@
+/* -*- mode: c; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: t -*-
+ * vim: ts=4 sw=4 noet ai cindent syntax=c
+ *
+ * prioqueue:  a simple priority queue implementation
+ *
+ * The queue organises it's data internally using a doubly linked
+ * list, into which elements are inserted at the right position. This
+ * is definitely not the best algorithm for a priority queue, but it
+ * fits best for the given purpose, i.e. the top process sorting.
+ * This means we have a rather little amount of total elements (~200
+ * on a normal system), which are to be inserted into a queue of only
+ * the few top-most elements (10 at the current state). Additionally,
+ * at each update interval, the queue is drained completely and
+ * refilled from scratch.
+ *
+ * Copyright (C) 2009 Phil Sutter <phil@nwl.cc>
+ *
+ * Initially based on the former implementation of sorted processes in
+ * top.c, Copyright (C) 2005 David Carter <boojit@pundo.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <limits.h>	/* INT_MAX */
+#include <stdlib.h>
+#include <string.h>
+
+struct prio_elem {
+	struct prio_elem *next, *prev;
+	void *data;
+};
+
+struct prio_queue {
+	/* Compare a and b. Return:
+	 * <0 if a should come before b,
+	 * >0 if b should come before a,
+	 *  0 if don't care */
+	int (*compare)(void *a, void *b);
+
+	/* Free element payload. Called when dropping elements. */
+	void (*free)(void *a);
+
+	/* Maximum size of queue. The first
+	 * elements in the list take precedence. */
+	int max_size;
+
+	/* The pointers to the actual list. */
+	struct prio_elem *head, *tail;
+
+	/* The current number of elements in the list. */
+	int cur_size;
+};
+
+/* nop callback to save us from conditional calling */
+static void pq_free_nop(void *a) { (void)a; }
+
+struct prio_queue *init_prio_queue(void)
+{
+	struct prio_queue *retval;
+
+	retval = malloc(sizeof(struct prio_queue));
+	memset(retval, 0, sizeof(struct prio_queue));
+
+	/* use pq_free_nop by default */
+	retval->free = &pq_free_nop;
+
+	/* Default to maximum possible size as restricted
+	 * by the used data type. This also saves us from
+	 * checking if caller has set this field or not. */
+	retval->max_size = INT_MAX;
+
+	return retval;
+}
+
+void pq_set_compare(struct prio_queue *queue, int (*pqcompare)(void *a, void *b))
+{
+	if (pqcompare)
+		queue->compare = pqcompare;
+}
+
+void pq_set_free(struct prio_queue *queue, void (*pqfree)(void *a))
+{
+	if (pqfree)
+		queue->free = pqfree;
+}
+
+void pq_set_max_size(struct prio_queue *queue, int max_size)
+{
+	if (max_size >= 0)
+		queue->max_size = max_size;
+}
+
+int pq_get_cur_size(struct prio_queue *queue)
+{
+	return queue->cur_size;
+}
+
+static struct prio_elem *init_prio_elem(void *data)
+{
+	struct prio_elem *retval;
+
+	retval = malloc(sizeof(struct prio_elem));
+	memset(retval, 0, sizeof(struct prio_elem));
+
+	retval->data = data;
+	return retval;
+}
+
+void insert_prio_elem(struct prio_queue *queue, void *data)
+{
+	struct prio_elem *cur;
+
+	/* queue->compare is a must-have */
+	if (!queue->compare)
+		return;
+
+	/* empty queue, insert the first item */
+	if (!queue->cur_size) {
+		queue->cur_size++;
+		queue->head = queue->tail = init_prio_elem(data);
+		return;
+	}
+
+	/* short-cut 1: new item is lower than all others */
+	if (queue->compare(queue->tail->data, data) <= 0) {
+		if (queue->cur_size < queue->max_size) {
+			queue->cur_size++;
+			queue->tail->next = init_prio_elem(data);
+			queue->tail->next->prev = queue->tail;
+			queue->tail = queue->tail->next;
+		} else	/* list was already full */
+			(*queue->free)(data);
+		return;
+	}
+
+	/* short-cut 2: we have a new maximum */
+	if (queue->compare(queue->head->data, data) >= 0) {
+		queue->cur_size++;
+		queue->head->prev = init_prio_elem(data);
+		queue->head->prev->next = queue->head;
+		queue->head = queue->head->prev;
+		goto check_cur_size;
+	}
+
+	/* find the actual position if short-cuts failed */
+	for (cur = queue->head->next; cur; cur = cur->next) {
+		if (queue->compare(cur->data, data) >= 0) {
+			queue->cur_size++;
+			cur->prev->next = init_prio_elem(data);
+			cur->prev->next->prev = cur->prev;
+			cur->prev->next->next = cur;
+			cur->prev = cur->prev->next;
+			break;
+		}
+	}
+
+check_cur_size:
+	/* drop the lowest item if queue overrun */
+	if (queue->cur_size > queue->max_size) {
+		queue->cur_size--;
+		queue->tail = queue->tail->prev;
+		(*queue->free)(queue->tail->next->data);
+		free(queue->tail->next);
+		queue->tail->next = NULL;
+	}
+}
+
+void *pop_prio_elem(struct prio_queue *queue)
+{
+	struct prio_elem *tmp;
+	void *data;
+
+	if (queue->cur_size <= 0)
+		return NULL;
+
+	tmp = queue->head;
+	data = tmp->data;
+
+	queue->head = queue->head->next;
+	queue->cur_size--;
+	if (queue->head)
+		queue->head->prev = NULL;
+	else	/* list is now empty */
+		queue->tail = NULL;
+
+	free(tmp);
+	return data;
+}
+
+void free_prio_queue(struct prio_queue *queue)
+{
+	void *data;
+	while((data = pop_prio_elem(queue)))
+		(*queue->free)(data);
+	free(queue);
+}

src/prioqueue.h

@@ -0,0 +1,66 @@
+/* -*- mode: c; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: t -*-
+ * vim: ts=4 sw=4 noet ai cindent syntax=c
+ *
+ * prioqueue:  a simple priority queue implementation
+ *
+ * Copyright (C) 2009 Phil Sutter <phil@nwl.cc>
+ *
+ * Initially based on the former implementation of sorted processes in
+ * top.c, Copyright (C) 2005 David Carter <boojit@pundo.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef _PRIOQUEUE_H
+#define _PRIOQUEUE_H
+
+/* forward-define for private data */
+struct prio_queue;
+
+/* typedef for a distinct prioqueue object */
+typedef struct prio_queue *prio_queue_t;
+
+/* initialise a prioqueue object (mandatory) */
+prio_queue_t init_prio_queue(void);
+
+/* set the compare function (mandatory)
+ * (*compare) shall return:
+ * <0 if a should come before b,
+ * >0 if b should come before a,
+ *  0 if doesn't matter */
+void pq_set_compare(prio_queue_t, int (*compare)(void *a, void *b));
+
+/* set the data free function (optional)
+ * (*free) will be called when:
+ * - dropping elements from the end of a limited size queue and
+ * - free_prio_queue() finds leftover elements in the given queue */
+void pq_set_free(prio_queue_t, void (*free)(void *));
+
+/* set a maximum queue size (optional) (defaults to INT_MAX) */
+void pq_set_max_size(prio_queue_t, int);
+
+/* insert an element into the given queue */
+void insert_prio_elem(prio_queue_t, void *);
+
+/* return the number of elements in the queue */
+int pq_get_cur_size(prio_queue_t queue);
+
+/* pop the top-most element from the queue
+ * returns NULL if queue is empty */
+void *pop_prio_elem(prio_queue_t);
+
+/* clear and free the given queue */
+void free_prio_queue(prio_queue_t);
+
+#endif /* _PRIOQUEUE_H */

src/top.c

@@ -29,6 +29,7 @@
  *
  */
 
+#include "prioqueue.h"
 #include "top.h"
 #include "logging.h"
 
@@ -595,25 +596,11 @@ static void calc_io_each(void)
  * Find the top processes				  *
  ******************************************/
 
-/* free a sp_process structure */
-static void free_sp(struct sorted_process *sp)
+/* cpu comparison function for prio queue */
+static int compare_cpu(void *va, void *vb)
 {
-	free(sp);
-}
+	struct process *a = va, *b = vb;
 
-/* create a new sp_process structure */
-static struct sorted_process *malloc_sp(struct process *proc)
-{
-	struct sorted_process *sp;
-	sp = malloc(sizeof(struct sorted_process));
-	memset(sp, 0, sizeof(struct sorted_process));
-	sp->proc = proc;
-	return sp;
-}
-
-/* cpu comparison function for insert_sp_element */
-static int compare_cpu(struct process *a, struct process *b)
-{
 	if (a->amount < b->amount) {
 		return 1;
 	} else if (a->amount > b->amount) {
@@ -623,9 +610,11 @@ static int compare_cpu(struct process *a, struct process *b)
 	}
 }
 
-/* mem comparison function for insert_sp_element */
-static int compare_mem(struct process *a, struct process *b)
+/* mem comparison function for prio queue */
+static int compare_mem(void *va, void *vb)
 {
+	struct process *a = va, *b = vb;
+
 	if (a->rss < b->rss) {
 		return 1;
 	} else if (a->rss > b->rss) {
@@ -635,16 +624,20 @@ static int compare_mem(struct process *a, struct process *b)
 	}
 }
 
-/* CPU time comparision function for insert_sp_element */
-static int compare_time(struct process *a, struct process *b)
+/* CPU time comparision function for prio queue */
+static int compare_time(void *va, void *vb)
 {
+	struct process *a = va, *b = vb;
+
 	return b->total_cpu_time - a->total_cpu_time;
 }
 
 #ifdef IOSTATS
-/* I/O comparision function for insert_sp_element */
-static int compare_io(struct process *a, struct process *b)
+/* I/O comparision function for prio queue */
+static int compare_io(void *va, void *vb)
 {
+	struct process *a = va, *b = vb;
+
 	if (a->io_perc < b->io_perc) {
 		return 1;
 	} else if (a->io_perc > b->io_perc) {
@@ -655,78 +648,6 @@ static int compare_io(struct process *a, struct process *b)
 }
 #endif /* IOSTATS */
 
-/* insert this process into the list in a sorted fashion,
- * or destroy it if it doesn't fit on the list */
-static int insert_sp_element(struct sorted_process *sp_cur,
-		struct sorted_process **p_sp_head, struct sorted_process **p_sp_tail,
-		int max_elements, int compare_funct(struct process *, struct process *))
-{
-
-	struct sorted_process *sp_readthru = NULL, *sp_destroy = NULL;
-	int did_insert = 0, x = 0;
-
-	if (*p_sp_head == NULL) {
-		*p_sp_head = sp_cur;
-		*p_sp_tail = sp_cur;
-		return 1;
-	}
-	for (sp_readthru = *p_sp_head, x = 0;
-			sp_readthru != NULL && x < max_elements;
-			sp_readthru = sp_readthru->less, x++) {
-		if (compare_funct(sp_readthru->proc, sp_cur->proc) > 0 && !did_insert) {
-			/* sp_cur is bigger than sp_readthru
-			 * so insert it before sp_readthru */
-			sp_cur->less = sp_readthru;
-			if (sp_readthru == *p_sp_head) {
-				/* insert as the new head of the list */
-				*p_sp_head = sp_cur;
-			} else {
-				/* insert inside the list */
-				sp_readthru->greater->less = sp_cur;
-				sp_cur->greater = sp_readthru->greater;
-			}
-			sp_readthru->greater = sp_cur;
-			/* element was inserted, so increase the counter */
-			did_insert = ++x;
-		}
-	}
-	if (x < max_elements && sp_readthru == NULL && !did_insert) {
-		/* sp_cur is the smallest element and list isn't full,
-		 * so insert at the end */
-		(*p_sp_tail)->less = sp_cur;
-		sp_cur->greater = *p_sp_tail;
-		*p_sp_tail = sp_cur;
-		did_insert = x;
-	} else if (x >= max_elements) {
-		/* We inserted an element and now the list is too big by one.
-		 * Destroy the smallest element */
-		sp_destroy = *p_sp_tail;
-		*p_sp_tail = sp_destroy->greater;
-		(*p_sp_tail)->less = NULL;
-		free_sp(sp_destroy);
-	}
-	if (!did_insert) {
-		/* sp_cur wasn't added to the sorted list, so destroy it */
-		free_sp(sp_cur);
-	}
-	return did_insert;
-}
-
-/* copy the procs in the sorted list to the array, and destroy the list */
-static void sp_acopy(struct sorted_process *sp_head, struct process **ar, int max_size)
-{
-	struct sorted_process *sp_cur, *sp_tmp;
-	int x;
-
-	sp_cur = sp_head;
-	for (x = 0; x < max_size && sp_cur != NULL; x++) {
-		ar[x] = sp_cur->proc;
-		sp_tmp = sp_cur;
-		sp_cur = sp_cur->less;
-		free_sp(sp_tmp);
-	}
-}
-
 /* ****************************************************************** *
  * Get a sorted list of the top cpu hogs and top mem hogs.			  *
  * Results are stored in the cpu,mem arrays in decreasing order[0-9]. *
@@ -739,14 +660,14 @@ void process_find_top(struct process **cpu, struct process **mem,
 #endif /* IOSTATS */
 		)
 {
-	struct sorted_process *spc_head = NULL, *spc_tail = NULL, *spc_cur = NULL;
-	struct sorted_process *spm_head = NULL, *spm_tail = NULL, *spm_cur = NULL;
-	struct sorted_process *spt_head = NULL, *spt_tail = NULL, *spt_cur = NULL;
+	prio_queue_t cpu_queue, mem_queue, time_queue
 #ifdef IOSTATS
-	struct sorted_process *spi_head = NULL, *spi_tail = NULL, *spi_cur = NULL;
-#endif /* IOSTATS */
+		, io_queue
+#endif
+		;
 	struct process *cur_proc = NULL;
 	unsigned long long total = 0;
+	int i;
 
 	if (!top_cpu && !top_mem && !top_time
 #ifdef IOSTATS
@@ -757,6 +678,24 @@ void process_find_top(struct process **cpu, struct process **mem,
 		return;
 	}
 
+	cpu_queue = init_prio_queue();
+	pq_set_compare(cpu_queue, &compare_cpu);
+	pq_set_max_size(cpu_queue, MAX_SP);
+
+	mem_queue = init_prio_queue();
+	pq_set_compare(mem_queue, &compare_mem);
+	pq_set_max_size(mem_queue, MAX_SP);
+
+	time_queue = init_prio_queue();
+	pq_set_compare(time_queue, &compare_time);
+	pq_set_max_size(time_queue, MAX_SP);
+
+#ifdef IOSTATS
+	io_queue = init_prio_queue();
+	pq_set_compare(io_queue, &compare_io);
+	pq_set_max_size(io_queue, MAX_SP);
+#endif
+
 	total = calc_cpu_total();	/* calculate the total of the processor */
 	update_process_table();		/* update the table with process list */
 	calc_cpu_each(total);		/* and then the percentage for each task */
@@ -769,35 +708,39 @@ void process_find_top(struct process **cpu, struct process **mem,
 
 	while (cur_proc != NULL) {
 		if (top_cpu) {
-			spc_cur = malloc_sp(cur_proc);
-			insert_sp_element(spc_cur, &spc_head, &spc_tail, MAX_SP,
-					&compare_cpu);
+			insert_prio_elem(cpu_queue, cur_proc);
 		}
 		if (top_mem) {
-			spm_cur = malloc_sp(cur_proc);
-			insert_sp_element(spm_cur, &spm_head, &spm_tail, MAX_SP,
-					&compare_mem);
+			insert_prio_elem(mem_queue, cur_proc);
 		}
 		if (top_time) {
-			spt_cur = malloc_sp(cur_proc);
-			insert_sp_element(spt_cur, &spt_head, &spt_tail, MAX_SP,
-					&compare_time);
+			insert_prio_elem(time_queue, cur_proc);
 		}
 #ifdef IOSTATS
 		if (top_io) {
-			spi_cur = malloc_sp(cur_proc);
-			insert_sp_element(spi_cur, &spi_head, &spi_tail, MAX_SP,
-					&compare_io);
+			insert_prio_elem(io_queue, cur_proc);
 		}
 #endif /* IOSTATS */
 		cur_proc = cur_proc->next;
 	}
 
-	if (top_cpu)	sp_acopy(spc_head, cpu,		MAX_SP);
-	if (top_mem)	sp_acopy(spm_head, mem,		MAX_SP);
-	if (top_time)	sp_acopy(spt_head, ptime,	MAX_SP);
+	for (i = 0; i < MAX_SP; i++) {
+		if (top_cpu)
+			cpu[i] = pop_prio_elem(cpu_queue);
+		if (top_mem)
+			mem[i] = pop_prio_elem(mem_queue);
+		if (top_time)
+			ptime[i] = pop_prio_elem(time_queue);
 #ifdef IOSTATS
-	if (top_io)		sp_acopy(spi_head, io,		MAX_SP);
+		if (top_io)
+			io[i] = pop_prio_elem(io_queue);
+#endif /* IOSTATS */
+	}
+	free_prio_queue(cpu_queue);
+	free_prio_queue(mem_queue);
+	free_prio_queue(time_queue);
+#ifdef IOSTATS
+	free_prio_queue(io_queue);
 #endif /* IOSTATS */
 }