[PATCH 5.15 076/139] net/mlx5: DR, Cache STE shadow memory

Greg Kroah-Hartman
2022-02-28T17:54:22Z

From: Yevgeny Kliteynik <kliteyn@nvidia.com>

commit e5b2bc30c21139ae10f0e56989389d0bc7b7b1d6 upstream.

During rule insertion on each ICM memory chunk we also allocate shadow memory
used for management. This includes the hw_ste, dr_ste and miss list per entry.
Since the scale of these allocations is large we noticed a performance hiccup
that happens once malloc and free are stressed.
In extreme usecases when ~1M chunks are freed at once, it might take up to 40
seconds to complete this, up to the point the kernel sees this as self-detected
stall on CPU:

rcu: INFO: rcu_sched self-detected stall on CPU

To resolve this we will increase the reuse of shadow memory.
Doing this we see that a time in the aforementioned usecase dropped from ~40
seconds to ~8-10 seconds.

Fixes: 29cf8febd185 ("net/mlx5: DR, ICM pool memory allocator")
Signed-off-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c | 109 ++++++----
drivers/net/ethernet/mellanox/mlx5/core/steering/mlx5dr.h | 5
2 files changed, 79 insertions(+), 35 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
@@ -136,37 +136,35 @@ static void dr_icm_pool_mr_destroy(struc
kvfree(icm_mr);
}

-static int dr_icm_chunk_ste_init(struct mlx5dr_icm_chunk *chunk)
+static int dr_icm_buddy_get_ste_size(struct mlx5dr_icm_buddy_mem *buddy)
{
- chunk->ste_arr = kvzalloc(chunk->num_of_entries *
- sizeof(chunk->ste_arr[0]), GFP_KERNEL);
- if (!chunk->ste_arr)
- return -ENOMEM;
-
- chunk->hw_ste_arr = kvzalloc(chunk->num_of_entries *
- DR_STE_SIZE_REDUCED, GFP_KERNEL);
- if (!chunk->hw_ste_arr)
- goto out_free_ste_arr;
-
- chunk->miss_list = kvmalloc(chunk->num_of_entries *
- sizeof(chunk->miss_list[0]), GFP_KERNEL);
- if (!chunk->miss_list)
- goto out_free_hw_ste_arr;
+ /* We support only one type of STE size, both for ConnectX-5 and later
+ * devices. Once the support for match STE which has a larger tag is
+ * added (32B instead of 16B), the STE size for devices later than
+ * ConnectX-5 needs to account for that.
+ */
+ return DR_STE_SIZE_REDUCED;
+}

- return 0;
+static void dr_icm_chunk_ste_init(struct mlx5dr_icm_chunk *chunk, int offset)
+{
+ struct mlx5dr_icm_buddy_mem *buddy = chunk->buddy_mem;
+ int index = offset / DR_STE_SIZE;

-out_free_hw_ste_arr:
- kvfree(chunk->hw_ste_arr);
-out_free_ste_arr:
- kvfree(chunk->ste_arr);
- return -ENOMEM;
+ chunk->ste_arr = &buddy->ste_arr[index];
+ chunk->miss_list = &buddy->miss_list[index];
+ chunk->hw_ste_arr = buddy->hw_ste_arr +
+ index * dr_icm_buddy_get_ste_size(buddy);
}

static void dr_icm_chunk_ste_cleanup(struct mlx5dr_icm_chunk *chunk)
{
- kvfree(chunk->miss_list);
- kvfree(chunk->hw_ste_arr);
- kvfree(chunk->ste_arr);
+ struct mlx5dr_icm_buddy_mem *buddy = chunk->buddy_mem;
+
+ memset(chunk->hw_ste_arr, 0,
+ chunk->num_of_entries * dr_icm_buddy_get_ste_size(buddy));
+ memset(chunk->ste_arr, 0,
+ chunk->num_of_entries * sizeof(chunk->ste_arr[0]));
}

static enum mlx5dr_icm_type
@@ -189,6 +187,44 @@ static void dr_icm_chunk_destroy(struct
kvfree(chunk);
}

+static int dr_icm_buddy_init_ste_cache(struct mlx5dr_icm_buddy_mem *buddy)
+{
+ int num_of_entries =
+ mlx5dr_icm_pool_chunk_size_to_entries(buddy->pool->max_log_chunk_sz);
+
+ buddy->ste_arr = kvcalloc(num_of_entries,
+ sizeof(struct mlx5dr_ste), GFP_KERNEL);
+ if (!buddy->ste_arr)
+ return -ENOMEM;
+
+ /* Preallocate full STE size on non-ConnectX-5 devices since
+ * we need to support both full and reduced with the same cache.
+ */
+ buddy->hw_ste_arr = kvcalloc(num_of_entries,
+ dr_icm_buddy_get_ste_size(buddy), GFP_KERNEL);
+ if (!buddy->hw_ste_arr)
+ goto free_ste_arr;
+
+ buddy->miss_list = kvmalloc(num_of_entries * sizeof(struct list_head), GFP_KERNEL);
+ if (!buddy->miss_list)
+ goto free_hw_ste_arr;
+
+ return 0;
+
+free_hw_ste_arr:
+ kvfree(buddy->hw_ste_arr);
+free_ste_arr:
+ kvfree(buddy->ste_arr);
+ return -ENOMEM;
+}
+
+static void dr_icm_buddy_cleanup_ste_cache(struct mlx5dr_icm_buddy_mem *buddy)
+{
+ kvfree(buddy->ste_arr);
+ kvfree(buddy->hw_ste_arr);
+ kvfree(buddy->miss_list);
+}
+
static int dr_icm_buddy_create(struct mlx5dr_icm_pool *pool)
{
struct mlx5dr_icm_buddy_mem *buddy;
@@ -208,11 +244,19 @@ static int dr_icm_buddy_create(struct ml
buddy->icm_mr = icm_mr;
buddy->pool = pool;

+ if (pool->icm_type == DR_ICM_TYPE_STE) {
+ /* Reduce allocations by preallocating and reusing the STE structures */
+ if (dr_icm_buddy_init_ste_cache(buddy))
+ goto err_cleanup_buddy;
+ }
+
/* add it to the -start- of the list in order to search in it first */
list_add(&buddy->list_node, &pool->buddy_mem_list);

return 0;

+err_cleanup_buddy:
+ mlx5dr_buddy_cleanup(buddy);
err_free_buddy:
kvfree(buddy);
free_mr:
@@ -234,6 +278,9 @@ static void dr_icm_buddy_destroy(struct

mlx5dr_buddy_cleanup(buddy);

+ if (buddy->pool->icm_type == DR_ICM_TYPE_STE)
+ dr_icm_buddy_cleanup_ste_cache(buddy);
+
kvfree(buddy);
}

@@ -261,26 +308,18 @@ dr_icm_chunk_create(struct mlx5dr_icm_po
chunk->byte_size =
mlx5dr_icm_pool_chunk_size_to_byte(chunk_size, pool->icm_type);
chunk->seg = seg;
+ chunk->buddy_mem = buddy_mem_pool;

- if (pool->icm_type == DR_ICM_TYPE_STE && dr_icm_chunk_ste_init(chunk)) {
- mlx5dr_err(pool->dmn,
- "Failed to init ste arrays (order: %d)\n",
- chunk_size);
- goto out_free_chunk;
- }
+ if (pool->icm_type == DR_ICM_TYPE_STE)
+ dr_icm_chunk_ste_init(chunk, offset);

buddy_mem_pool->used_memory += chunk->byte_size;
- chunk->buddy_mem = buddy_mem_pool;
INIT_LIST_HEAD(&chunk->chunk_list);

/* chunk now is part of the used_list */
list_add_tail(&chunk->chunk_list, &buddy_mem_pool->used_list);

return chunk;
-
-out_free_chunk:
- kvfree(chunk);
- return NULL;
}

static bool dr_icm_pool_is_sync_required(struct mlx5dr_icm_pool *pool)
--- a/drivers/net/ethernet/mellanox/mlx5/core/steering/mlx5dr.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/mlx5dr.h
@@ -160,6 +160,11 @@ struct mlx5dr_icm_buddy_mem {
* sync_ste command sets them free.
*/
struct list_head hot_list;
+
+ /* Memory optimisation */
+ struct mlx5dr_ste *ste_arr;
+ struct list_head *miss_list;
+ u8 *hw_ste_arr;
};

int mlx5dr_buddy_init(struct mlx5dr_icm_buddy_mem *buddy,