Commit 380207d0 authored by Philipp Reisner's avatar Philipp Reisner

drbd: Load balancing of read requests

New config option for the disk secition "read-balancing", with
the values: prefer-local, prefer-remote, round-robin, when-congested-remote.
Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent d10b4ea3
......@@ -698,6 +698,7 @@ enum {
AHEAD_TO_SYNC_SOURCE, /* Ahead -> SyncSource queued */
B_RS_H_DONE, /* Before resync handler done (already executed) */
DISCARD_MY_DATA, /* discard_my_data flag per volume */
READ_BALANCE_RR,
};
struct drbd_bitmap; /* opaque for drbd_conf */
......
......@@ -4974,7 +4974,7 @@ static int got_NegDReply(struct drbd_tconn *tconn, struct packet_info *pi)
update_peer_seq(mdev, be32_to_cpu(p->seq_num));
dev_err(DEV, "Got NegDReply; Sector %llus, len %u; Fail original request.\n",
dev_err(DEV, "Got NegDReply; Sector %llus, len %u.\n",
(unsigned long long)sector, be32_to_cpu(p->blksize));
return validate_req_change_req_state(mdev, p->block_id, sector,
......
......@@ -563,6 +563,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)
atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
if (!(req->rq_state & RQ_WRITE) &&
mdev->state.disk == D_UP_TO_DATE &&
!IS_ERR_OR_NULL(req->private_bio))
goto goto_read_retry_local;
/* if it is still queued, we may not complete it here.
* it will be canceled soon. */
if (!(req->rq_state & RQ_NET_QUEUED))
......@@ -625,10 +630,22 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
req->rq_state |= RQ_NET_DONE;
if (!(req->rq_state & RQ_WRITE) &&
mdev->state.disk == D_UP_TO_DATE &&
!IS_ERR_OR_NULL(req->private_bio))
goto goto_read_retry_local;
_req_may_be_done_not_susp(req, m);
/* else: done by HANDED_OVER_TO_NETWORK */
break;
goto_read_retry_local:
req->rq_state |= RQ_LOCAL_PENDING;
req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
generic_make_request(req->private_bio);
break;
case FAIL_FROZEN_DISK_IO:
if (!(req->rq_state & RQ_LOCAL_COMPLETED))
break;
......@@ -689,6 +706,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
dec_ap_pending(mdev);
req->rq_state &= ~RQ_NET_PENDING;
req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
if (!IS_ERR_OR_NULL(req->private_bio)) {
bio_put(req->private_bio);
req->private_bio = NULL;
put_ldev(mdev);
}
_req_may_be_done_not_susp(req, m);
break;
};
......@@ -723,6 +745,35 @@ static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int
return drbd_bm_count_bits(mdev, sbnr, ebnr) == 0;
}
static bool remote_due_to_read_balancing(struct drbd_conf *mdev)
{
enum drbd_read_balancing rbm;
struct backing_dev_info *bdi;
if (mdev->state.pdsk < D_UP_TO_DATE)
return false;
rcu_read_lock();
rbm = rcu_dereference(mdev->ldev->disk_conf)->read_balancing;
rcu_read_unlock();
switch (rbm) {
case RB_CONGESTED_REMOTE:
bdi = &mdev->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
return bdi_read_congested(bdi);
case RB_LEAST_PENDING:
return atomic_read(&mdev->local_cnt) >
atomic_read(&mdev->ap_pending_cnt) + atomic_read(&mdev->rs_pending_cnt);
case RB_ROUND_ROBIN:
return test_and_change_bit(READ_BALANCE_RR, &mdev->flags);
case RB_PREFER_REMOTE:
return true;
case RB_PREFER_LOCAL:
default:
return false;
}
}
/*
* complete_conflicting_writes - wait for any conflicting write requests
*
......@@ -790,6 +841,10 @@ int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long s
bio_put(req->private_bio);
req->private_bio = NULL;
put_ldev(mdev);
} else if (remote_due_to_read_balancing(mdev)) {
/* Keep the private bio in case we need it
for a local retry */
local = 0;
}
}
remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
......@@ -1017,7 +1072,7 @@ fail_free_complete:
if (req->rq_state & RQ_IN_ACT_LOG)
drbd_al_complete_io(mdev, &req->i);
fail_and_free_req:
if (local) {
if (!IS_ERR_OR_NULL(req->private_bio)) {
bio_put(req->private_bio);
req->private_bio = NULL;
put_ldev(mdev);
......
......@@ -102,6 +102,14 @@ enum drbd_on_congestion {
OC_DISCONNECT,
};
enum drbd_read_balancing {
RB_PREFER_LOCAL,
RB_PREFER_REMOTE,
RB_ROUND_ROBIN,
RB_LEAST_PENDING,
RB_CONGESTED_REMOTE,
};
/* KEEP the order, do not delete or insert. Only append. */
enum drbd_ret_code {
ERR_CODE_BASE = 100,
......
......@@ -129,6 +129,7 @@ GENL_struct(DRBD_NLA_DISK_CONF, 3, disk_conf,
__flg_field_def(18, DRBD_GENLA_F_MANDATORY, disk_drain, DRBD_DISK_DRAIN_DEF)
__flg_field_def(19, DRBD_GENLA_F_MANDATORY, md_flushes, DRBD_MD_FLUSHES_DEF)
__u32_field_def(20, DRBD_GENLA_F_MANDATORY, disk_timeout, DRBD_DISK_TIMEOUT_DEF)
__u32_field_def(21, 0 /* OPTIONAL */, read_balancing, DRBD_READ_BALANCING_DEF)
)
GENL_struct(DRBD_NLA_RESOURCE_OPTS, 4, res_opts,
......
......@@ -161,6 +161,7 @@
#define DRBD_RR_CONFLICT_DEF ASB_DISCONNECT
#define DRBD_ON_NO_DATA_DEF OND_IO_ERROR
#define DRBD_ON_CONGESTION_DEF OC_BLOCK
#define DRBD_READ_BALANCING_DEF RB_PREFER_LOCAL
#define DRBD_MAX_BIO_BVECS_MIN 0
#define DRBD_MAX_BIO_BVECS_MAX 128
......
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