Re: [PATCH 01/11] block: add support for carrying stream information in a bio

[Jens Axboe]

On 06/14/2017 02:37 PM, Christoph Hellwig wrote:
> Btw, I think these could also easily map to DSM field in the NVMe
> write command, except that these unfortunately mix in read information
> as well.

But that's the problem, they are read/write mixed flags. I'd much
rather keep them separate. If some application finds it useful
to specify read access patterns, we should have separate flags for
those imho.

-- 
Jens Axboe

Re: [PATCH 01/11] block: add support for carrying stream information in a bio

[Christoph Hellwig]

Btw, I think these could also easily map to DSM field in the NVMe
write command, except that these unfortunately mix in read information
as well.

> + __REQ_WRITE_SHORT,  /* short life time write */

-> Frequent writes and infrequent reads to the LBA range indicated.

or

-> Frequent writes and frequent reads to the LBA range indicated.

> + __REQ_WRITE_MEDIUM, /* medium life time write */

-> Typical number of reads and writes expected for this LBA range.

> + __REQ_WRITE_LONG,   /* long life time write */

-> Infrequent writes and infrequent reads to the LBA range indicated.

or

-> Infrequent writes and frequent reads to the LBA range indicated.

> + __REQ_WRITE_EXTREME,/* extremely long life time write */

-> One time write. E.g. command is due to virus scan, backup, file
copy, or archive.

Re: [PATCH 01/11] block: add support for carrying stream information in a bio

[Andreas Dilger]

On Jun 13, 2017, at 11:15 AM, Jens Axboe  wrote:
> 
> No functional changes in this patch, but it allows each bio to
> carry a stream ID and disallows merging of bio's with different
> stream IDs.
> 
> Signed-off-by: Jens Axboe 

Reviewed-by: Andreas Dilger 

> ---
> block/bio.c   |  2 ++
> block/blk-merge.c | 14 ++
> include/linux/blk_types.h | 17 +
> 3 files changed, 33 insertions(+)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 888e7801c638..77f4be1f7428 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -595,6 +595,7 @@ void __bio_clone_fast(struct bio *bio, struct bio 
> *bio_src)
>   bio->bi_opf = bio_src->bi_opf;
>   bio->bi_iter = bio_src->bi_iter;
>   bio->bi_io_vec = bio_src->bi_io_vec;
> + bio->bi_stream = bio_src->bi_stream;
> 
>   bio_clone_blkcg_association(bio, bio_src);
> }
> @@ -678,6 +679,7 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t 
> gfp_mask,
>   bio->bi_opf = bio_src->bi_opf;
>   bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
>   bio->bi_iter.bi_size= bio_src->bi_iter.bi_size;
> + bio->bi_stream  = bio_src->bi_stream;
> 
>   switch (bio_op(bio)) {
>   case REQ_OP_DISCARD:
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 3990ae406341..28998acdd675 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -693,6 +693,13 @@ static struct request *attempt_merge(struct 
> request_queue *q,
>   return NULL;
> 
>   /*
> +  * Don't allow merge of different streams, or for a stream with
> +  * non-stream IO.
> +  */
> + if (req->bio->bi_stream != next->bio->bi_stream)
> + return NULL;
> +
> + /*
>* If we are allowed to merge, then append bio list
>* from next to rq and release next. merge_requests_fn
>* will have updated segment counts, update sector
> @@ -811,6 +818,13 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
>   !blk_write_same_mergeable(rq->bio, bio))
>   return false;
> 
> + /*
> +  * Don't allow merge of different streams, or for a stream with
> +  * non-stream IO.
> +  */
> + if (rq->bio->bi_stream != bio->bi_stream)
> + return false;
> +
>   return true;
> }
> 
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 61339bc44400..1940876a7fa7 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -36,6 +36,8 @@ struct bio {
>   unsigned short  bi_flags;   /* status, etc and bvec pool 
> number */
>   unsigned short  bi_ioprio;
> 
> + unsigned intbi_stream;  /* write life time hint */
> +
>   struct bvec_iterbi_iter;
> 
>   /* Number of segments in this BIO after
> @@ -312,4 +314,19 @@ struct blk_rq_stat {
>   u64 batch;
> };
> 
> +static inline void bio_set_streamid(struct bio *bio, unsigned int stream)
> +{
> + bio->bi_stream = stream;
> +}
> +
> +static inline bool bio_stream_valid(struct bio *bio)
> +{
> + return bio->bi_stream != 0;
> +}
> +
> +static inline unsigned int bio_stream(struct bio *bio)
> +{
> + return bio->bi_stream;
> +}
> +
> #endif /* __LINUX_BLK_TYPES_H */
> --
> 2.7.4
> 


Cheers, Andreas







signature.asc
Description: Message signed with OpenPGP