Commit f86d6f9c authored by Michal Schmidt's avatar Michal Schmidt Committed by Tony Nguyen
Browse files

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



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: default avatarBrent Rowsell <browsell@redhat.com>
Signed-off-by: default avatarMichal Schmidt <mschmidt@redhat.com>
Reviewed-by: default avatarArkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: default avatarSimon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
parent 84817ab6

drivers/net/ethernet/intel/ice/ice_common.c

+7 −7
Original line number Diff line number Diff line
@@ -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));

}



/**

drivers/net/ethernet/intel/ice/ice_controlq.c

+5 −4
Original line number Diff line number Diff line
@@ -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)) {

drivers/net/ethernet/intel/ice/ice_controlq.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */