Hi, Scsi MQ makes a large static allocation for the first scatter gather list chunk for the driver to use. This is a performance headache we'd like to fix by reducing the size of the allocation to a 2 element array. Doing this will break the current guarantee that any driver using SG_ALL doesn't need to use the scatterlist iterators and can get away with directly dereferencing the array. Thus we need to update all drivers to use the scatterlist iterators and remove direct indexing of the scatterlist array before reducing the initial scatterlist allocation size in SCSI. So convert drivers to use scatterlist helper. There are two types of scsi SGL uses: 1) operate on scsi_sglist(scmd) directly, then one local variable of 'struct scatterlist *' is involved, so the following coccinelle semantic patch is developed for finding this type of direct sgl uses: https://marc.info/?l=linux-scsi&m=156031374809852&w=2 2) scsi_sglist(scmd) is stored to cmd->SCp.buffer and the SGL is used via cmd->SCp.buffer. Simple 'grep SCp.buffer' is used for finding SGL direct uses, fortunately only the following drivers uses SCp.buffer to store SGL: NCR5380, aha152x, arm/, imm, pcmcia, ppa and wd33c93 And arm/ is already ready to handle chained SGL. The 1st 9 patches are for handling type #1, and the other 6 patches for handling type #2. V3: - update commit log and cover letter, most of words are from James Bottomley V2: - use coccinelle semantic patch for finding direct sgl uses from scsi command(9 drivers found) - run 'git grep -E "SCp.buffer"' to find direct sgl uses from SCp.buffer(6 drivers are found) Finn Thain (1): NCR5380: Support chained sg lists Ming Lei (14): scsi: vmw_pscsi: use sg helper to operate scatterlist scsi: advansys: use sg helper to operate scatterlist scsi: lpfc: use sg helper to operate scatterlist scsi: mvumi: use sg helper to operate scatterlist scsi: ipr: use sg helper to operate scatterlist scsi: pmcraid: use sg helper to operate scatterlist usb: image: microtek: use sg helper to operate scatterlist staging: unisys: visorhba: use sg helper to operate scatterlist s390: zfcp_fc: use sg helper to operate scatterlist scsi: aha152x: use sg helper to operate scatterlist scsi: imm: use sg helper to operate scatterlist scsi: pcmcia: nsp_cs: use sg helper to operate scatterlist scsi: ppa: use sg helper to operate scatterlist scsi: wd33c93: use sg helper to operate scatterlist drivers/s390/scsi/zfcp_fc.c | 4 +- drivers/scsi/NCR5380.c | 41 ++++++++----------- drivers/scsi/advansys.c | 2 +- drivers/scsi/aha152x.c | 29 ++++++++----- drivers/scsi/imm.c | 2 +- drivers/scsi/ipr.c | 28 +++++++------ drivers/scsi/lpfc/lpfc_nvmet.c | 3 +- drivers/scsi/mvumi.c | 9 ++-- drivers/scsi/pcmcia/nsp_cs.c | 4 +- drivers/scsi/pmcraid.c | 12 +++--- drivers/scsi/ppa.c | 2 +- drivers/scsi/vmw_pvscsi.c | 2 +- drivers/scsi/wd33c93.c | 2 +- .../staging/unisys/visorhba/visorhba_main.c | 9 ++-- drivers/usb/image/microtek.c | 20 ++++----- drivers/usb/image/microtek.h | 2 +- 16 files changed, 85 insertions(+), 86 deletions(-) -- 2.20.1
