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Commit bc97f4bb authored by Rob Evers's avatar Rob Evers Committed by James Bottomley
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[SCSI] scsi_dh_alua: backoff alua rtpg retry linearly vs. geometrically 



Currently the backoff algorithm for when to retry alua rtpg
requests progresses geometrically as so:

2, 4, 8, 16, 32, 64... seconds.

This progression can lead to un-needed delay in retrying
alua rtpg requests when the rtpgs are delayed.  A less
aggressive backoff algorithm that is additive would not
lead to such large jumps when delays start getting long, but
would backoff linearly:

2, 4, 6, 8, 10... seconds.

Signed-off-by: default avatarMartin George <marting@netapp.com>
Signed-off-by: default avatarRob Evers <revers@redhat.com>
Reviewed-by: default avatarBabu Moger <babu.moger@netapp.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 8e67ce60

drivers/scsi/device_handler/scsi_dh_alua.c

+2 −2
Original line number Diff line number Diff line
@@ -527,7 +527,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h) 
	unsigned char *ucp;

	unsigned err;

	bool rtpg_ext_hdr_req = 1;

	unsigned long expiry, interval = 1000;

	unsigned long expiry, interval = 0;

	unsigned int tpg_desc_tbl_off;

	unsigned char orig_transition_tmo;
@@ -632,7 +632,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h) 
	case TPGS_STATE_TRANSITIONING:

		if (time_before(jiffies, expiry)) {

			/* State transition, retry */

			interval *= 2;

			interval += 2000;

			msleep(interval);

			goto retry;

		}