From 38b253f3b6c6c975aa8a5660ab19fa44a7804297 Mon Sep 17 00:00:00 2001
From: Vincent Fu <vincent.fu@wdc.com>
Date: Tue, 30 Jul 2019 12:07:26 -0400
Subject: [PATCH] smalloc: print debug info on oom error

Provide more details about the request and the state of the memory pools
when smalloc encounters an oom situation.
---
 smalloc.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 smalloc.h |  1 +
 2 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/smalloc.c b/smalloc.c
index a2ad25a0..c1ae08bd 100644
--- a/smalloc.c
+++ b/smalloc.c
@@ -48,6 +48,12 @@ struct block_hdr {
 #endif
 };
 
+/*
+ * This suppresses the voluminous potential bitmap printout when
+ * smalloc encounters an OOM error
+ */
+static const bool enable_smalloc_debug = false;
+
 static struct pool mp[MAX_POOLS];
 static unsigned int nr_pools;
 static unsigned int last_pool;
@@ -387,10 +393,9 @@ fail:
 	return ret;
 }
 
-static void *smalloc_pool(struct pool *pool, size_t size)
+static size_t size_to_alloc_size(size_t size)
 {
 	size_t alloc_size = size + sizeof(struct block_hdr);
-	void *ptr;
 
 	/*
 	 * Round to int alignment, so that the postred pointer will
@@ -401,6 +406,14 @@ static void *smalloc_pool(struct pool *pool, size_t size)
 	alloc_size = (alloc_size + int_mask) & ~int_mask;
 #endif
 
+	return alloc_size;
+}
+
+static void *smalloc_pool(struct pool *pool, size_t size)
+{
+	size_t alloc_size = size_to_alloc_size(size);
+	void *ptr;
+
 	ptr = __smalloc_pool(pool, alloc_size);
 	if (ptr) {
 		struct block_hdr *hdr = ptr;
@@ -415,6 +428,72 @@ static void *smalloc_pool(struct pool *pool, size_t size)
 	return ptr;
 }
 
+static void smalloc_print_bitmap(struct pool *pool)
+{
+	size_t nr_blocks = pool->nr_blocks;
+	unsigned int *bitmap = pool->bitmap;
+	unsigned int i, j;
+	char *buffer;
+
+	if (!enable_smalloc_debug)
+		return;
+
+	buffer = malloc(SMALLOC_BPI + 1);
+	if (!buffer)
+		return;
+	buffer[SMALLOC_BPI] = '\0';
+
+	for (i = 0; i < nr_blocks; i++) {
+		unsigned int line = bitmap[i];
+
+		/* skip completely full lines */
+		if (line == -1U)
+			continue;
+
+		for (j = 0; j < SMALLOC_BPI; j++)
+			if ((1 << j) & line)
+				buffer[SMALLOC_BPI-1-j] = '1';
+			else
+				buffer[SMALLOC_BPI-1-j] = '0';
+
+		log_err("smalloc: bitmap %5u, %s\n", i, buffer);
+	}
+
+	free(buffer);
+}
+
+void smalloc_debug(size_t size)
+{
+	unsigned int i;
+	size_t alloc_size = size_to_alloc_size(size);
+	size_t alloc_blocks;
+
+	alloc_blocks = size_to_blocks(alloc_size);
+
+	if (size)
+		log_err("smalloc: size = %lu, alloc_size = %lu, blocks = %lu\n",
+			(unsigned long) size, (unsigned long) alloc_size,
+			(unsigned long) alloc_blocks);
+	for (i = 0; i < nr_pools; i++) {
+		log_err("smalloc: pool %u, free/total blocks %u/%u\n", i,
+			(unsigned int) (mp[i].free_blocks),
+			(unsigned int) (mp[i].nr_blocks*sizeof(unsigned int)*8));
+		if (size && mp[i].free_blocks >= alloc_blocks) {
+			void *ptr = smalloc_pool(&mp[i], size);
+			if (ptr) {
+				sfree(ptr);
+				last_pool = i;
+				log_err("smalloc: smalloc_pool %u succeeded\n", i);
+			} else {
+				log_err("smalloc: smalloc_pool %u failed\n", i);
+				log_err("smalloc: next_non_full=%u, nr_blocks=%u\n",
+					(unsigned int) mp[i].next_non_full, (unsigned int) mp[i].nr_blocks);
+				smalloc_print_bitmap(&mp[i]);
+			}
+		}
+	}
+}
+
 void *smalloc(size_t size)
 {
 	unsigned int i, end_pool;
@@ -445,6 +524,7 @@ void *smalloc(size_t size)
 
 	log_err("smalloc: OOM. Consider using --alloc-size to increase the "
 		"shared memory available.\n");
+	smalloc_debug(size);
 	return NULL;
 }
 
diff --git a/smalloc.h b/smalloc.h
index 8df10e6f..1f7716f4 100644
--- a/smalloc.h
+++ b/smalloc.h
@@ -9,6 +9,7 @@ extern void sfree(void *);
 extern char *smalloc_strdup(const char *);
 extern void sinit(void);
 extern void scleanup(void);
+extern void smalloc_debug(size_t);
 
 extern unsigned int smalloc_pool_size;
 
-- 
2.25.1