Re: [PATCH v3] Fix one error in mthca_alloc
From: Leon Romanovsky <leon@kernel.org>
Date: 2021-08-31 09:52:26
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
quoted hunk ↗ jump to hunk
Signed-off-by: kangning <redacted> --- 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