Re: [PATCH 6/6] esp_scsi: Optimize PIO loops

From: Michael Schmitz
Date: Sat Oct 13 2018 - 00:18:59 EST


Hi Finn,

Am 13.10.2018 um 17:09 schrieb Finn Thain:
On Sat, 13 Oct 2018, Michael Schmitz wrote:

Hi Finn,

Am 13.10.2018 um 13:51 schrieb Finn Thain:
Avoid function calls in the inner PIO loops. On a Centris 660av this
improves throughput for sequential read transfers by about 40% and
sequential write by about 10%.

Unfortunately it is not possible to have method calls like esp_write8()
placed inline so this is always going to be slow (even with LTO).

Tested-by: Stan Johnson <userm57@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
---
drivers/scsi/esp_scsi.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 646701fc22a4..9f0e68cd0e99 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -2788,7 +2788,7 @@ static inline unsigned int esp_wait_for_fifo(struct
esp *esp)
if (fbytes)
return fbytes;

- udelay(2);
+ udelay(1);
} while (--i);

pr_err("FIFO is empty (sreg %02x)\n", esp_read8(ESP_STATUS));
@@ -2804,7 +2804,7 @@ static inline int esp_wait_for_intr(struct esp *esp)
if (esp->sreg & ESP_STAT_INTR)
return 0;

- udelay(2);
+ udelay(1);
} while (--i);

pr_err("IRQ timeout (sreg %02x)\n", esp->sreg);
@@ -2831,7 +2831,7 @@ void esp_send_pio_cmd(struct esp *esp, u32 addr, u32
esp_count,
if (!esp_wait_for_fifo(esp))
break;

- *dst++ = esp_read8(ESP_FDATA);
+ *dst++ = readb(esp->fifo_reg);
--esp_count;

if (!esp_count)
@@ -2852,15 +2852,15 @@ void esp_send_pio_cmd(struct esp *esp, u32 addr, u32
esp_count,
}

if (phase == ESP_MIP)
- scsi_esp_cmd(esp, ESP_CMD_MOK);
+ esp_write8(ESP_CMD_MOK, ESP_CMD);

You're no longer logging this command with this patch. (That'll be the reason
for the speedup you saw ...)


- scsi_esp_cmd(esp, ESP_CMD_TI);
+ esp_write8(ESP_CMD_TI, ESP_CMD);

Same here..

}
} else {
unsigned int n = ESP_FIFO_SIZE;
u8 *src = (u8 *)addr;

- scsi_esp_cmd(esp, ESP_CMD_FLUSH);
+ esp_write8(ESP_CMD_FLUSH, ESP_CMD);

here..


if (n > esp_count)
n = esp_count;
@@ -2894,7 +2894,7 @@ void esp_send_pio_cmd(struct esp *esp, u32 addr, u32
esp_count,
src += n;
esp_count -= n;

- scsi_esp_cmd(esp, ESP_CMD_TI);
+ esp_write8(ESP_CMD_TI, ESP_CMD);

and here.


Yes, it's deliberate.

I'm sure it was... and I wasn't objecting to that.

The burst of ESP_CMD_TI's in the log was quite useful to spot what went
wrong during PIO.

I don't think it's as useful as you seem to think. Compare
mac_esp_send_pdma_cmd().

Maybe mention in the changelog that commands during PIO are no longer
logged? Or introduce a new ESP_EVENT_PIO and log that at the start of
PIO?


Yes, and I did leave a scsi_esp_cmd(esp, cmd) call at the start of PIO.

Which I missed from just looking at the patch, sorry.

That should be sufficient, right?

It would indeed. Thanks for clarifying.

Cheers,

Michael