On 04/07/16 07:38, Christoph Hellwig wrote:
This is also very interesting for storage targets, which face the same issue. SCST has a mode where it caches some fully constructed SGLs, which is probably very similar to what NICs want to do.
I think a cached allocator for page sets + the scatterlists that describe these page sets would not only be useful for SCSI target implementations but also for the Linux SCSI initiator. Today the scsi-mq code reserves space in each scsi_cmnd for a scatterlist of SCSI_MAX_SG_SEGMENTS. If scatterlists would be cached together with page sets less memory would be needed per scsi_cmnd. See also scsi_mq_setup_tags() and scsi_alloc_sgtable().
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