| Message ID | 20170705041427.9887-1-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
mmio reads in the fast path are always a bad idea..
Reviewed-by: Christoph Hellwig <hch@lst.de>
On 07/04/2017 10:14 PM, Ming Lei wrote: > It is observed reading the register from HW takes a bit long, > for example in my box, the following difference of 'perf report > --no-children fio ...' can be seen when running I/O: > > 1) V4.12 without patch > + 9.28% fio [mtip32xx] [k] mtip_irq_handler > + 8.48% fio [mtip32xx] [k] mtip_init_cmd_header > > 2) V4.12 with the following patch > + 9.14% fio [mtip32xx] [k] mtip_irq_handler > ...... > + 1.14% fio [mtip32xx] [k] mtip_init_cmd_header > > IOPS can be increased by ~5% with this patch too. Thanks, this is definitely problematic since we don't just do it at init time anymore. Applied for 4.13.
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c index d8618a71da74..01e7fdfae0af 100644 --- a/drivers/block/mtip32xx/mtip32xx.c +++ b/drivers/block/mtip32xx/mtip32xx.c @@ -174,7 +174,6 @@ static void mtip_init_cmd_header(struct request *rq) { struct driver_data *dd = rq->q->queuedata; struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq); - u32 host_cap_64 = readl(dd->mmio + HOST_CAP) & HOST_CAP_64; /* Point the command headers at the command tables. */ cmd->command_header = dd->port->command_list + @@ -182,7 +181,7 @@ static void mtip_init_cmd_header(struct request *rq) cmd->command_header_dma = dd->port->command_list_dma + (sizeof(struct mtip_cmd_hdr) * rq->tag); - if (host_cap_64) + if (test_bit(MTIP_PF_HOST_CAP_64, &dd->port->flags)) cmd->command_header->ctbau = __force_bit2int cpu_to_le32((cmd->command_dma >> 16) >> 16); cmd->command_header->ctba = __force_bit2int cpu_to_le32(cmd->command_dma & 0xFFFFFFFF); @@ -386,6 +385,7 @@ static void mtip_init_port(struct mtip_port *port) port->mmio + PORT_LST_ADDR_HI); writel((port->rxfis_dma >> 16) >> 16, port->mmio + PORT_FIS_ADDR_HI); + set_bit(MTIP_PF_HOST_CAP_64, &port->flags); } writel(port->command_list_dma & 0xFFFFFFFF, diff --git a/drivers/block/mtip32xx/mtip32xx.h b/drivers/block/mtip32xx/mtip32xx.h index e8286af50e16..e20e55dab443 100644 --- a/drivers/block/mtip32xx/mtip32xx.h +++ b/drivers/block/mtip32xx/mtip32xx.h @@ -140,6 +140,7 @@ enum { (1 << MTIP_PF_SE_ACTIVE_BIT) | (1 << MTIP_PF_DM_ACTIVE_BIT) | (1 << MTIP_PF_TO_ACTIVE_BIT)), + MTIP_PF_HOST_CAP_64 = 10, /* cache HOST_CAP_64 */ MTIP_PF_SVC_THD_ACTIVE_BIT = 4, MTIP_PF_ISSUE_CMDS_BIT = 5,
It is observed reading the register from HW takes a bit long, for example in my box, the following difference of 'perf report --no-children fio ...' can be seen when running I/O: 1) V4.12 without patch + 9.28% fio [mtip32xx] [k] mtip_irq_handler + 8.48% fio [mtip32xx] [k] mtip_init_cmd_header 2) V4.12 with the following patch + 9.14% fio [mtip32xx] [k] mtip_irq_handler ...... + 1.14% fio [mtip32xx] [k] mtip_init_cmd_header IOPS can be increased by ~5% with this patch too. Fixes: a4e84aae8139(mtip32xx: use runtime tag to initialize command header) Signed-off-by: Ming Lei <ming.lei@redhat.com> --- drivers/block/mtip32xx/mtip32xx.c | 4 ++-- drivers/block/mtip32xx/mtip32xx.h | 1 + 2 files changed, 3 insertions(+), 2 deletions(-)