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From 0bf728030e0ad7a49e6e1737ea06ae74da9279d3 Mon Sep 17 00:00:00 2001
From: Xavi Hernandez <xhernandez@redhat.com>
Date: Fri, 21 Jun 2019 11:28:08 +0200
Subject: [PATCH 212/221] core: fix memory allocation issues
Two problems have been identified that caused that gluster's memory
usage were twice higher than required.
1. An off by 1 error caused that all objects allocated from the memory
pools were taken from a pool bigger than required. Since each pool
corresponds to a size equal to a power of two, this was wasting half
of the available memory.
2. The header information used for accounting on each memory object was
not taken into consideration when searching for a suitable memory
pool. It was added later when each individual block was allocated.
This made this space "invisible" to memory accounting.
Credits: Thanks to Nithya Balachandran for identifying this problem and
testing this patch.
Upstream patch:
> BUG: 1722802
> Upstream patch link: https://review.gluster.org/c/glusterfs/+/22921
> Change-Id: I90e27ad795fe51ca11c13080f62207451f6c138c
> Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>
Fixes: bz#1722801
Change-Id: I90e27ad795fe51ca11c13080f62207451f6c138c
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>
Reviewed-on: https://code.engineering.redhat.com/gerrit/174714
Tested-by: RHGS Build Bot <nigelb@redhat.com>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
---
libglusterfs/src/glusterfs/mem-pool.h | 5 ++-
libglusterfs/src/mem-pool.c | 57 +++++++++++++++++++----------------
2 files changed, 35 insertions(+), 27 deletions(-)
diff --git a/libglusterfs/src/glusterfs/mem-pool.h b/libglusterfs/src/glusterfs/mem-pool.h
index c5a486b..be0a26d 100644
--- a/libglusterfs/src/glusterfs/mem-pool.h
+++ b/libglusterfs/src/glusterfs/mem-pool.h
@@ -231,7 +231,10 @@ typedef struct pooled_obj_hdr {
struct mem_pool *pool;
} pooled_obj_hdr_t;
-#define AVAILABLE_SIZE(p2) (1 << (p2))
+/* Each memory block inside a pool has a fixed size that is a power of two.
+ * However each object will have a header that will reduce the available
+ * space. */
+#define AVAILABLE_SIZE(p2) ((1UL << (p2)) - sizeof(pooled_obj_hdr_t))
typedef struct per_thread_pool {
/* the pool that was used to request this allocation */
diff --git a/libglusterfs/src/mem-pool.c b/libglusterfs/src/mem-pool.c
index df167b6..d88041d 100644
--- a/libglusterfs/src/mem-pool.c
+++ b/libglusterfs/src/mem-pool.c
@@ -627,6 +627,7 @@ struct mem_pool *
mem_pool_new_fn(glusterfs_ctx_t *ctx, unsigned long sizeof_type,
unsigned long count, char *name)
{
+ unsigned long extra_size, size;
unsigned int power;
struct mem_pool *new = NULL;
struct mem_pool_shared *pool = NULL;
@@ -637,10 +638,25 @@ mem_pool_new_fn(glusterfs_ctx_t *ctx, unsigned long sizeof_type,
return NULL;
}
- /* We ensure sizeof_type > 1 and the next power of two will be, at least,
- * 2^POOL_SMALLEST */
- sizeof_type |= (1 << POOL_SMALLEST) - 1;
- power = sizeof(sizeof_type) * 8 - __builtin_clzl(sizeof_type - 1) + 1;
+ /* This is the overhead we'll have because of memory accounting for each
+ * memory block. */
+ extra_size = sizeof(pooled_obj_hdr_t);
+
+ /* We need to compute the total space needed to hold the data type and
+ * the header. Given that the smallest block size we have in the pools
+ * is 2^POOL_SMALLEST, we need to take the MAX(size, 2^POOL_SMALLEST).
+ * However, since this value is only needed to compute its rounded
+ * logarithm in base 2, and this only depends on the highest bit set,
+ * we can simply do a bitwise or with the minimum size. We need to
+ * subtract 1 for correct handling of sizes that are exactly a power
+ * of 2. */
+ size = (sizeof_type + extra_size - 1UL) | ((1UL << POOL_SMALLEST) - 1UL);
+
+ /* We compute the logarithm in base 2 rounded up of the resulting size.
+ * This value will identify which pool we need to use from the pools of
+ * powers of 2. This is equivalent to finding the position of the highest
+ * bit set. */
+ power = sizeof(size) * 8 - __builtin_clzl(size);
if (power > POOL_LARGEST) {
gf_msg_callingfn("mem-pool", GF_LOG_ERROR, EINVAL, LG_MSG_INVALID_ARG,
"invalid argument");
@@ -732,8 +748,8 @@ mem_get_pool_list(void)
return pool_list;
}
-pooled_obj_hdr_t *
-mem_get_from_pool(struct mem_pool *mem_pool, struct mem_pool_shared *pool)
+static pooled_obj_hdr_t *
+mem_get_from_pool(struct mem_pool *mem_pool)
{
per_thread_pool_list_t *pool_list;
per_thread_pool_t *pt_pool;
@@ -747,12 +763,7 @@ mem_get_from_pool(struct mem_pool *mem_pool, struct mem_pool_shared *pool)
return NULL;
}
- if (mem_pool) {
- pt_pool = &pool_list
- ->pools[mem_pool->pool->power_of_two - POOL_SMALLEST];
- } else {
- pt_pool = &pool_list->pools[pool->power_of_two - POOL_SMALLEST];
- }
+ pt_pool = &pool_list->pools[mem_pool->pool->power_of_two - POOL_SMALLEST];
(void)pthread_spin_lock(&pool_list->lock);
@@ -770,8 +781,7 @@ mem_get_from_pool(struct mem_pool *mem_pool, struct mem_pool_shared *pool)
} else {
(void)pthread_spin_unlock(&pool_list->lock);
GF_ATOMIC_INC(pt_pool->parent->allocs_stdc);
- retval = malloc((1 << pt_pool->parent->power_of_two) +
- sizeof(pooled_obj_hdr_t));
+ retval = malloc(1 << pt_pool->parent->power_of_two);
#ifdef DEBUG
hit = _gf_false;
#endif
@@ -779,19 +789,14 @@ mem_get_from_pool(struct mem_pool *mem_pool, struct mem_pool_shared *pool)
}
if (retval != NULL) {
- if (mem_pool) {
- retval->pool = mem_pool;
- retval->power_of_two = mem_pool->pool->power_of_two;
+ retval->pool = mem_pool;
+ retval->power_of_two = mem_pool->pool->power_of_two;
#ifdef DEBUG
- if (hit == _gf_true)
- GF_ATOMIC_INC(mem_pool->hit);
- else
- GF_ATOMIC_INC(mem_pool->miss);
+ if (hit == _gf_true)
+ GF_ATOMIC_INC(mem_pool->hit);
+ else
+ GF_ATOMIC_INC(mem_pool->miss);
#endif
- } else {
- retval->power_of_two = pool->power_of_two;
- retval->pool = NULL;
- }
retval->magic = GF_MEM_HEADER_MAGIC;
retval->pool_list = pool_list;
}
@@ -811,7 +816,7 @@ mem_get(struct mem_pool *mem_pool)
#if defined(GF_DISABLE_MEMPOOL)
return GF_MALLOC(mem_pool->sizeof_type, gf_common_mt_mem_pool);
#else
- pooled_obj_hdr_t *retval = mem_get_from_pool(mem_pool, NULL);
+ pooled_obj_hdr_t *retval = mem_get_from_pool(mem_pool);
if (!retval) {
return NULL;
}
--
1.8.3.1
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