staging/lustre/ptlrpc: avoid list scan in ptlrpcd_check

ptlrpcd_check() always scan all requests on ptlrpc_request_set
and try to finish completed requests, this is low efficiency.
Even worse, l_wait_event() always checks condition for twice
before sleeping and one more time after waking up, which means
it will call ptlrpcd_check() for three times in each loop.

This patch will move completed requests at the head of list
in ptlrpc_check_set(), with this change ptlrpcd_check doesn't
need to scan all requests anymore.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-on: http://review.whamcloud.com/11513
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5548
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 20 insertions, 15 deletions

diff --git a/drivers/staging/lustre/lustre/ptlrpc/client.c b/drivers/staging/lustre/lustre/ptlrpc/client.c
index dc9e406f3212..8c1ec830712f 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/client.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/client.c
@@ -1497,11 +1497,13 @@ static inline int ptlrpc_set_producer(struct ptlrpc_request_set *set)
 int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
 {
         struct list_head *tmp, *next;
+        struct list_head comp_reqs;
         int force_timer_recalc = 0;
 
         if (atomic_read(&set->set_remaining) == 0)
                 return 1;
 
+        INIT_LIST_HEAD(&comp_reqs);
         list_for_each_safe(tmp, next, &set->set_requests) {
                 struct ptlrpc_request *req =
                         list_entry(tmp, struct ptlrpc_request,
@@ -1576,8 +1578,10 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                         ptlrpc_rqphase_move(req, req->rq_next_phase);
                 }
 
-                if (req->rq_phase == RQ_PHASE_COMPLETE)
+                if (req->rq_phase == RQ_PHASE_COMPLETE) {
+                        list_move_tail(&req->rq_set_chain, &comp_reqs);
                         continue;
+                }
 
                 if (req->rq_phase == RQ_PHASE_INTERPRET)
                         goto interpret;
@@ -1860,9 +1864,15 @@ interpret:
                         if (req->rq_status != 0)
                                 set->set_rc = req->rq_status;
                         ptlrpc_req_finished(req);
+                } else {
+                        list_move_tail(&req->rq_set_chain, &comp_reqs);
                 }
         }
 
+        /* move completed request at the head of list so it's easier for
+         * caller to find them */
+        list_splice(&comp_reqs, &set->set_requests);
+
         /* If we hit an error, we want to recover promptly. */
         return atomic_read(&set->set_remaining) == 0 || force_timer_recalc;
 }
diff --git a/drivers/staging/lustre/lustre/ptlrpc/ptlrpcd.c b/drivers/staging/lustre/lustre/ptlrpc/ptlrpcd.c
index cbcc541cac43..4621b71fe0b6 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/ptlrpcd.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/ptlrpcd.c
@@ -306,21 +306,16 @@ static int ptlrpcd_check(struct lu_env *env, struct ptlrpcd_ctl *pc)
         if (atomic_read(&set->set_remaining))
                 rc |= ptlrpc_check_set(env, set);
 
-        if (!list_empty(&set->set_requests)) {
-                /*
-                 * XXX: our set never completes, so we prune the completed
-                 * reqs after each iteration. boy could this be smarter.
-                 */
-                list_for_each_safe(pos, tmp, &set->set_requests) {
-                        req = list_entry(pos, struct ptlrpc_request,
-                                             rq_set_chain);
-                        if (req->rq_phase != RQ_PHASE_COMPLETE)
-                                continue;
+        /* NB: ptlrpc_check_set has already moved completed request at the
+         * head of seq::set_requests */
+        list_for_each_safe(pos, tmp, &set->set_requests) {
+                req = list_entry(pos, struct ptlrpc_request, rq_set_chain);
+                if (req->rq_phase != RQ_PHASE_COMPLETE)
+                        break;
 
-                        list_del_init(&req->rq_set_chain);
-                        req->rq_set = NULL;
-                        ptlrpc_req_finished(req);
-                }
+                list_del_init(&req->rq_set_chain);
+                req->rq_set = NULL;
+                ptlrpc_req_finished(req);
         }
 
         if (rc == 0) {