diff options
| author | Ming Lei <ming.lei@redhat.com> | 2019-04-28 15:39:32 +0800 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2019-06-20 15:21:33 -0400 |
| commit | 3dccdf53c2f38399b11085ded4447ce1467f006c (patch) | |
| tree | d5415d9704bd5dc2151e36363e5b6cfa0a1dd087 /drivers/scsi/scsi_lib.c | |
| parent | 92524fa12312d1f082a473e14c590c48b4ef3fe5 (diff) | |
scsi: core: avoid preallocating big SGL for data
scsi_mq_setup_tags() preallocates a big buffer for the IO SGL. The size is
based on scsi_mq_sgl_size() which is determined based on
shost->sg_tablesize and SG_CHUNK_SIZE.
Modern DMA engines are often capable of dealing with very big segments so
the resulting scsi_mq_sgl_size() is often too big. SG_CHUNK_SIZE results in
a static 4KB SGL allocation per command.
If an HBA has lots of deep queues, preallocation for the sg list can
consume substantial amounts of memory. For lpfc, nr_hw_queues can be 70
and each queue's depth 3781. This means the resulting preallocation for
the data SGL is 70*3781*2K = 517MB.
Switch to runtime allocation for SGL for lists longer than 2 entries. This
is the approach used by NVMe PCI so it should be reasonable for SCSI as
well. Runtime SGL allocation has always been the case for the legacy I/O
path so this is nothing new.
[mkp: attempted to clarify commit desc]
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi/scsi_lib.c')
| -rw-r--r-- | drivers/scsi/scsi_lib.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index c115458c835e..45b43e97505c 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -45,6 +45,8 @@ */ #define SCSI_INLINE_PROT_SG_CNT 1 +#define SCSI_INLINE_SG_CNT 2 + static struct kmem_cache *scsi_sdb_cache; static struct kmem_cache *scsi_sense_cache; static struct kmem_cache *scsi_sense_isadma_cache; @@ -547,7 +549,8 @@ static void scsi_uninit_cmd(struct scsi_cmnd *cmd) static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd) { if (cmd->sdb.table.nents) - sg_free_table_chained(&cmd->sdb.table, SG_CHUNK_SIZE); + sg_free_table_chained(&cmd->sdb.table, + SCSI_INLINE_SG_CNT); if (scsi_prot_sg_count(cmd)) sg_free_table_chained(&cmd->prot_sdb->table, SCSI_INLINE_PROT_SG_CNT); @@ -984,7 +987,7 @@ static blk_status_t scsi_init_sgtable(struct request *req, */ if (unlikely(sg_alloc_table_chained(&sdb->table, blk_rq_nr_phys_segments(req), sdb->table.sgl, - SG_CHUNK_SIZE))) + SCSI_INLINE_SG_CNT))) return BLK_STS_RESOURCE; /* @@ -1550,9 +1553,9 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd) } /* Size in bytes of the sg-list stored in the scsi-mq command-private data. */ -static unsigned int scsi_mq_sgl_size(struct Scsi_Host *shost) +static unsigned int scsi_mq_inline_sgl_size(struct Scsi_Host *shost) { - return min_t(unsigned int, shost->sg_tablesize, SG_CHUNK_SIZE) * + return min_t(unsigned int, shost->sg_tablesize, SCSI_INLINE_SG_CNT) * sizeof(struct scatterlist); } @@ -1734,7 +1737,7 @@ static int scsi_mq_init_request(struct blk_mq_tag_set *set, struct request *rq, if (scsi_host_get_prot(shost)) { sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size; - cmd->prot_sdb = (void *)sg + scsi_mq_sgl_size(shost); + cmd->prot_sdb = (void *)sg + scsi_mq_inline_sgl_size(shost); } return 0; @@ -1828,7 +1831,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) { unsigned int cmd_size, sgl_size; - sgl_size = scsi_mq_sgl_size(shost); + sgl_size = scsi_mq_inline_sgl_size(shost); cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size; if (scsi_host_get_prot(shost)) cmd_size += sizeof(struct scsi_data_buffer) + |