On Fri, Aug 27, 2021 at 08:52:28AM +0800, kangning wrote:
> drivers/infiniband/hw/mthca/mthca_allocator.c: alloc->last left unchanged in mthca_alloc, which
> has impact on performance of function find_next_zero_bit in mthca_alloc.
I don't know what the sentence above means, but the change is unlikely
to be correct.
When alloc->last starts to be equal to alloc->max, the
find_next_zero_bit() will always return alloc->max. which will ensure
that the following code is executed.
48 if (obj >= alloc->max) {
49 alloc->top = (alloc->top + alloc->max) & alloc->mask;
50 obj = find_first_zero_bit(alloc->table, alloc->max);
51 }
However the mthca_alloc() function has other error, it returns -1 while
based on its declaration it needs to be unsigned,
Thanks
>
> Signed-off-by: kangning <kangning18z@xxxxxxxxx>
> ---
>
> I squashed two commits into one in this version.
>
> drivers/infiniband/hw/mthca/mthca_allocator.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/infiniband/hw/mthca/mthca_allocator.c b/drivers/infiniband/hw/mthca/mthca_allocator.c
> index aef1d274a14e..1141695093e7 100644
> --- a/drivers/infiniband/hw/mthca/mthca_allocator.c
> +++ b/drivers/infiniband/hw/mthca/mthca_allocator.c
> @@ -51,6 +51,9 @@ u32 mthca_alloc(struct mthca_alloc *alloc)
> }
>
> if (obj < alloc->max) {
> + alloc->last = obj + 1;
> + if (alloc->last == alloc->max)
> + alloc->last = 0;
> set_bit(obj, alloc->table);
> obj |= alloc->top;
> } else
> --
> 2.17.1
>
