On 10/22/20 08:58, Logan Gunthorpe wrote:
>
>
> On 2020-10-21 7:02 p.m., Chaitanya Kulkarni wrote:
>> In nvmet_passthru_execute_cmd() which is a high frequency function
>> it uses bio_alloc() which leads to memory allocation from the fs pool
>> for each I/O.
>>
>> For NVMeoF nvmet_req we already have inline_bvec allocated as a part of
>> request allocation that can be used with preallocated bio when we
>> already know the size of request before bio allocation with bio_alloc(),
>> which we already do.
>>
>> Introduce a bio member for the nvmet_req passthru anon union. In the
>> fast path, check if we can get away with inline bvec and bio from
>> nvmet_req with bio_init() call before actually allocating from the
>> bio_alloc().
>>
>> This will be useful to avoid any new memory allocation under high
>> memory pressure situation and get rid of any extra work of
>> allocation (bio_alloc()) vs initialization (bio_init()) when
>> transfer len is < NVMET_MAX_INLINE_DATA_LEN that user can configure at
>> compile time.
>>
>> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
>> ---
>> drivers/nvme/target/nvmet.h | 1 +
>> drivers/nvme/target/passthru.c | 20 ++++++++++++++++++--
>> 2 files changed, 19 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
>> index 559a15ccc322..408a13084fb4 100644
>> --- a/drivers/nvme/target/nvmet.h
>> +++ b/drivers/nvme/target/nvmet.h
>> @@ -330,6 +330,7 @@ struct nvmet_req {
>> struct work_struct work;
>> } f;
>> struct {
>> + struct bio inline_bio;
>> struct request *rq;
>> struct work_struct work;
>> bool use_workqueue;
>> diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
>> index 496ffedb77dc..32498b4302cc 100644
>> --- a/drivers/nvme/target/passthru.c
>> +++ b/drivers/nvme/target/passthru.c
>> @@ -178,6 +178,14 @@ static void nvmet_passthru_req_done(struct request *rq,
>> blk_mq_free_request(rq);
>> }
>>
>> +static void nvmet_passthru_bio_done(struct bio *bio)
>> +{
>> + struct nvmet_req *req = bio->bi_private;
>> +
>> + if (bio != &req->p.inline_bio)
>> + bio_put(bio);
>> +}
>> +
>> static int nvmet_passthru_map_sg(struct nvmet_req *req, struct request *rq)
>> {
>> int sg_cnt = req->sg_cnt;
>> @@ -186,13 +194,21 @@ static int nvmet_passthru_map_sg(struct nvmet_req *req, struct request *rq)
>> int i;
>>
>> bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
>> - bio->bi_end_io = bio_put;
>> + if (req->transfer_len <= NVMET_MAX_INLINE_DATA_LEN) {
>> + bio = &req->p.inline_bio;
>> + bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
>> + } else {
>> + bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
>> + }
>> +
>> + bio->bi_end_io = nvmet_passthru_bio_done;
> I still think it's cleaner to change bi_endio for the inline/alloc'd
> cases by simply setting bi_endi_io to bio_put() only in the bio_alloc
> case. This should also be more efficient as it's one less indirect call
> and condition for the inline case.
>
> Besides that, the entire series looks good to me.
>
> Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
>
> Logan
>
Sagi/Christoph, any comments on this one ?
This series been sitting out for a while now.
