From: Bob Pearson <rpearsonhpe@gmail.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
Zhu Yanjun <zyjzyj2000@gmail.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH for-next 3/6] RDMA/rxe: Save object pointer in pool element
Date: Thu, 21 Oct 2021 12:21:15 -0500 [thread overview]
Message-ID: <394c9270-77bb-1195-9422-bd2d5715e2bd@gmail.com> (raw)
In-Reply-To: <20211020232051.GA28606@nvidia.com>
On 10/20/21 6:20 PM, Jason Gunthorpe wrote:
> On Sun, Oct 10, 2021 at 06:59:28PM -0500, Bob Pearson wrote:
>> In rxe_pool.c currently there are many cases where it is necessary to
>> compute the offset from a pool element struct to the object containing
>> the pool element in a type independent way. By saving a pointer to the
>> object when they are created extra work can be saved.
>>
>> Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
>> ---
>> drivers/infiniband/sw/rxe/rxe_pool.c | 16 +++++++++-------
>> drivers/infiniband/sw/rxe/rxe_pool.h | 1 +
>> 2 files changed, 10 insertions(+), 7 deletions(-)
>
> This would be better to just add a static_assert or build_bug_on that
> the offsetof() the rxe_pool_entry == 0. There is no reason for these
> to be sprinkled at every offset
>
> Then you don't need to do anything at all
>
> Jason
>
I think you missed something. Once upon a time all the rxe objects had the local
pool entry struct followed by the ib_xx struct and then anything else needed locally.
As Leon has been moving the allocations to rdma-core he had to make the ib_xx struct
first followed by the pool element. So there is a mish mash of offsets. Some
are/were 0, and the rest are all different depending on the size of the struct from
rdma-core. E.g. sizeof(struct ib_mr) != sizeof(struct ib_qp), etc. In order to make
the API simple and consistent I use a macro to convert from object to pool elem. e.g.
#define some_function(void *obj) __some_function(&obj->elem)
but to convert back from elem to obj we need to subtract some random offset e.g.
obj = elem->obj;
without knowing the type of obj which is simpler than what we had before, roughly
struct rxe_pool_info *info = &pool_info[elem->pool->type];
obj = (u8 *)(elem - info->elem_offset);
next prev parent reply other threads:[~2021-10-21 17:21 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-10 23:59 [PATCH for-next 0/6] RDMA/rxe: Fix potential races Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 1/6] RDMA/rxe: Make rxe_alloc() take pool lock Bob Pearson
2021-10-20 23:16 ` Jason Gunthorpe
2021-10-21 17:46 ` Bob Pearson
2021-10-25 12:43 ` Jason Gunthorpe
2021-10-25 18:48 ` Robert Pearson
2021-10-10 23:59 ` [PATCH for-next 2/6] RDMA/rxe: Copy setup parameters into rxe_pool Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 3/6] RDMA/rxe: Save object pointer in pool element Bob Pearson
2021-10-20 23:20 ` Jason Gunthorpe
2021-10-21 17:21 ` Bob Pearson [this message]
2021-10-25 15:40 ` Jason Gunthorpe
2021-10-10 23:59 ` [PATCH for-next 4/6] RDMA/rxe: Combine rxe_add_index with rxe_alloc Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 5/6] RDMA/rxe: Combine rxe_add_key " Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 6/6] RDMA/rxe: Fix potential race condition in rxe_pool Bob Pearson
2021-10-20 23:23 ` Jason Gunthorpe
2021-10-12 6:34 ` [PATCH for-next 0/6] RDMA/rxe: Fix potential races Leon Romanovsky
2021-10-12 20:19 ` Bob Pearson
2021-10-19 13:07 ` Leon Romanovsky
2021-10-19 16:35 ` Bob Pearson
2021-10-19 18:43 ` Jason Gunthorpe
2021-10-19 22:51 ` Bob Pearson
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