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[SCSI] scsi_dh_alua: backoff alua rtpg retry linearly vs. geometrically

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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: Martin George <marting@netapp.com>
Signed-off-by: Rob Evers <revers@redhat.com>
Reviewed-by: Babu Moger <babu.moger@netapp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Rob Evers 2012-05-18 14:08:56 -04:00 committed by James Bottomley
parent 8e67ce6072
commit bc97f4bb44
1 changed files with 2 additions and 2 deletions
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4
drivers/scsi/device_handler/scsi_dh_alua.c
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@ -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;
}