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ice: sleep, don't busy-wait, for ICE_CTL_Q_SQ_CMD_TIMEOUT

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The driver polls for ice_sq_done() with a 100 µs period for up to 1 s
and it uses udelay to do that.

Let's use usleep_range instead. We know sleeping is allowed here,
because we're holding a mutex (cq->sq_lock). To preserve the total
max waiting time, measure the timeout in jiffies.

ICE_CTL_Q_SQ_CMD_TIMEOUT is used also in ice_release_res(), but there
the polling period is 1 ms (i.e. 10 times longer). Since the timeout was
expressed in terms of the number of loops, the total timeout in this
function is 10 s. I do not know if this is intentional. This patch keeps
it.

The patch lowers the CPU usage of the ice-gnss-<dev_name> kernel thread
on my system from ~8 % to less than 1 %.

I received a report of high CPU usage with ptp4l where the busy-waiting
in ice_sq_send_cmd dominated the profile. This patch has been tested in
that usecase too and it made a huge improvement there.

Tested-by: Brent Rowsell <browsell@redhat.com>
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
This commit is contained in:
Michal Schmidt 2023-04-12 10:19:27 +02:00 committed by Tony Nguyen
parent 84817ab66f
commit f86d6f9c49
3 changed files with 13 additions and 12 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

14
drivers/net/ethernet/intel/ice/ice_common.c
View file

@ -1992,19 +1992,19 @@ ice_acquire_res(struct ice_hw *hw, enum ice_aq_res_ids res,
*/
void ice_release_res(struct ice_hw *hw, enum ice_aq_res_ids res)
{
u32 total_delay = 0;
unsigned long timeout;
int status;
status = ice_aq_release_res(hw, res, 0, NULL);
/* there are some rare cases when trying to release the resource
* results in an admin queue timeout, so handle them correctly
*/
while ((status == -EIO) && (total_delay < ICE_CTL_Q_SQ_CMD_TIMEOUT)) {
mdelay(1);
timeout = jiffies + 10 * ICE_CTL_Q_SQ_CMD_TIMEOUT;
do {
status = ice_aq_release_res(hw, res, 0, NULL);
total_delay++;
}
if (status != -EIO)
break;
usleep_range(1000, 2000);
} while (time_before(jiffies, timeout));
}
/**

9
drivers/net/ethernet/intel/ice/ice_controlq.c
View file

@ -964,7 +964,7 @@ ice_sq_send_cmd(struct ice_hw *hw, struct ice_ctl_q_info *cq,
struct ice_aq_desc *desc_on_ring;
bool cmd_completed = false;
struct ice_sq_cd *details;
u32 total_delay = 0;
unsigned long timeout;
int status = 0;
u16 retval = 0;
u32 val = 0;
@ -1057,13 +1057,14 @@ ice_sq_send_cmd(struct ice_hw *hw, struct ice_ctl_q_info *cq,
cq->sq.next_to_use = 0;
wr32(hw, cq->sq.tail, cq->sq.next_to_use);
timeout = jiffies + ICE_CTL_Q_SQ_CMD_TIMEOUT;
do {
if (ice_sq_done(hw, cq))
break;
udelay(ICE_CTL_Q_SQ_CMD_USEC);
total_delay++;
} while (total_delay < ICE_CTL_Q_SQ_CMD_TIMEOUT);
usleep_range(ICE_CTL_Q_SQ_CMD_USEC,
ICE_CTL_Q_SQ_CMD_USEC * 3 / 2);
} while (time_before(jiffies, timeout));
/* if ready, copy the desc back to temp */
if (ice_sq_done(hw, cq)) {

2
drivers/net/ethernet/intel/ice/ice_controlq.h
View file

@ -34,7 +34,7 @@ enum ice_ctl_q {
};
/* Control Queue timeout settings - max delay 1s */
#define ICE_CTL_Q_SQ_CMD_TIMEOUT 10000 /* Count 10000 times */
#define ICE_CTL_Q_SQ_CMD_TIMEOUT HZ /* Wait max 1s */
#define ICE_CTL_Q_SQ_CMD_USEC 100 /* Check every 100usec */
#define ICE_CTL_Q_ADMIN_INIT_TIMEOUT 10 /* Count 10 times */
#define ICE_CTL_Q_ADMIN_INIT_MSEC 100 /* Check every 100msec */