scsi: hisi_sas: Reduce HISI_SAS_SGE_PAGE_CNT in size

Macro HISI_SAS_SGE_PAGE_CNT is defined to SG_CHUNK_SIZE, which is 128.

This means that sizeof(struct hisi_sas_slot_buf_table) is 4192. This is
just over a 4K, which can mean inefficient DMA memory usage (for no PI).

Reduce the size of HISI_SAS_SGE_PAGE_CNT to 124 to fit in a 4K page. With
this change, we experience no performance hit.

Cc: dann frazier <dann.frazier@canonical.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/hisi_sas/hisi_sas.h b/drivers/scsi/hisi_sas/hisi_sas.h
index fc87994..06f22fb 100644 (file)
--- a/drivers/scsi/hisi_sas/hisi_sas.h
+++ b/drivers/scsi/hisi_sas/hisi_sas.h
@@ -484,12 +484,12 @@ struct hisi_sas_command_table_stp {
        u8      atapi_cdb[ATAPI_CDB_LEN];
 };
 
-#define HISI_SAS_SGE_PAGE_CNT SG_CHUNK_SIZE
+#define HISI_SAS_SGE_PAGE_CNT (124)
 struct hisi_sas_sge_page {
        struct hisi_sas_sge sge[HISI_SAS_SGE_PAGE_CNT];
 }  __aligned(16);
 
-#define HISI_SAS_SGE_DIF_PAGE_CNT   SG_CHUNK_SIZE
+#define HISI_SAS_SGE_DIF_PAGE_CNT   HISI_SAS_SGE_PAGE_CNT
 struct hisi_sas_sge_dif_page {
        struct hisi_sas_sge sge[HISI_SAS_SGE_DIF_PAGE_CNT];
 }  __aligned(16);