2022-11-25 12:32:21

by Christophe JAILLET

[permalink] [raw]
Subject: [PATCH 4/5] octeontx2-af: Fix the size of memory allocated for the 'id_bmap' bitmap

This allocation is really spurious.
The size of the bitmap is 'tot_ids' and it is used as such in the driver.

So we could expect something like:
table->id_bmap = devm_kcalloc(rvu->dev, BITS_TO_LONGS(table->tot_ids),
sizeof(long), GFP_KERNEL);

However, when the bitmap is allocated, we allocate:
BITS_TO_LONGS(table->tot_ids) * table->tot_ids ~=
table->tot_ids / 32 * table->tot_ids ~=
table->tot_ids^2 / 32

It is proportional to the square of 'table->tot_ids' which seems to
potentially be big.

Allocate the expected amount of memory, and switch to the bitmap API to
have it more straightforward.

Signed-off-by: Christophe JAILLET <[email protected]>
This patch is speculative.

If I'm right, I'm curious to know if 'able->tot_ids' can really get big
(I'm just guessing) , and if yes, how much.
drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
index 3f94b620ef5a..ae34746341c4 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
@@ -1914,8 +1914,8 @@ int rvu_npc_exact_init(struct rvu *rvu)
dev_dbg(rvu->dev, "%s: Allocated bitmap for 32 entry cam\n", __func__);

table->tot_ids = (table->mem_table.depth * table->mem_table.ways) + table->cam_table.depth;
- table->id_bmap = devm_kcalloc(rvu->dev, BITS_TO_LONGS(table->tot_ids),
- table->tot_ids, GFP_KERNEL);
+ table->id_bmap = devm_bitmap_zalloc(rvu->dev, table->tot_ids,

if (!table->id_bmap)
return -ENOMEM;