mem_fb: keep spare pages on a free list

Snapshotting made page alloc/free more frequent, and
modules/mixer really hammers on snapshots in fade mode... drizzle
as well, but mixer snapshots both module outputs per frame.

So by keeping these around the reclaimed page snapshots can be
held onto at within the fb as spares for quicker allocation.  In
practice it should just hit a high water mark of a working set
for spare pages, once in a steady state, assuming snapshots
aren't leaking.

Future commits will replicate this change in {drm,sdl}_fb

1 files changed, 22 insertions, 6 deletions

diff --git a/src/mem_fb.c b/src/mem_fb.c
index 2dfa5bb..fc9406b 100644
--- a/src/mem_fb.c
+++ b/src/mem_fb.c
@@ -11,7 +11,7 @@
 typedef struct mem_fb_page_t mem_fb_page_t;
 
 struct mem_fb_page_t {
-	void			*unused;
+	mem_fb_page_t		*next_spare;
 	uint32_t		buf[];
 };
 
@@ -22,6 +22,7 @@ typedef struct mem_fb_setup_t {
 
 typedef struct mem_fb_t {
 	mem_fb_setup_t		setup;
+	mem_fb_page_t		*spare_pages;
 } mem_fb_t;
 
 
@@ -90,9 +91,15 @@ _err:
 static void mem_fb_shutdown(til_fb_t *fb, void *context)
 {
 	mem_fb_t	*c = context;
+	mem_fb_page_t	*p;
 
 	assert(c);
 
+	while ((p = c->spare_pages)) {
+		c->spare_pages = p->next_spare;
+		free(p);
+	}
+
 	free(c);
 }
 
@@ -111,11 +118,18 @@ static void mem_fb_release(til_fb_t *fb, void *context)
 static void * mem_fb_page_alloc(til_fb_t *fb, void *context, til_fb_fragment_t *res_fragment)
 {
 	mem_fb_t	*c = context;
-	mem_fb_page_t	*p;
+	mem_fb_page_t	*p = NULL;
 
-	p = calloc(1, sizeof(mem_fb_page_t) + c->setup.width * c->setup.height * sizeof(uint32_t));
-	if (!p)
-		return NULL;
+	if (c->spare_pages) {
+		p = c->spare_pages;
+		c->spare_pages = p->next_spare;
+	}
+
+	if (!p) {
+		p = calloc(1, sizeof(mem_fb_page_t) + c->setup.width * c->setup.height * sizeof(uint32_t));
+		if (!p)
+			return NULL;
+	}
 
 	*res_fragment =	(til_fb_fragment_t){
 				.buf = p->buf,
@@ -132,9 +146,11 @@ static void * mem_fb_page_alloc(til_fb_t *fb, void *context, til_fb_fragment_t *
 
 static int mem_fb_page_free(til_fb_t *fb, void *context, void *page)
 {
+	mem_fb_t	*c = context;
 	mem_fb_page_t	*p = page;
 
-	free(p);
+	p->next_spare = c->spare_pages;
+	c->spare_pages = p;
 
 	return 0;
 }