write-behind: Allow trickling-writes to be configurable, fix usage of page_size and window_size

Summary:
- It adds a configurable option for "trickling-writes".
- Makes `__wb_preprocess_winds()` use `wb_inode->window_conf` rather
  than `page_size`, so that the window-size option is actually
  respected.
- This is a port of D3576122 & D3738605 to 3.8.

Test Plan:
- Prove test which looks @ brick-level FOPs and ensures
that they fall in the right write-size bucket.

Reviewed By: rwareing

Signature: t1:3576122:1468892648:6923a6a19b18888577ce5173b5c9cb9531f941e7

Change-Id: I379a9f2f0c4768c9052b7e9dd71c5f0469cb2d68
Signed-off-by: Shreyas Siravara <sshreyas@fb.com>
Reviewed-on: http://review.gluster.org/16079
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Kevin Vigor <kvigor@fb.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>

2 files changed, 22 insertions, 4 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-volume-set.c b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
index ac484e246b1..e82339a537f 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volume-set.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
@@ -1560,6 +1560,18 @@ struct volopt_map_entry glusterd_volopt_map[] = {
           .op_version = 2,
           .flags      = OPT_FLAG_CLIENT_OPT
         },
+        { .key        = "performance.write-behind-trickling-writes",
+          .voltype    = "performance/write-behind",
+          .option     = "trickling-writes",
+          .op_version = 2,
+          .flags      = OPT_FLAG_CLIENT_OPT
+        },
+        { .key        = "performance.nfs.write-behind-trickling-writes",
+          .voltype    = "performance/write-behind",
+          .option     = "trickling-writes",
+          .op_version = 2,
+          .flags      = OPT_FLAG_CLIENT_OPT
+        },
         { .key        = "performance.lazy-open",
           .voltype    = "performance/open-behind",
           .option     = "lazy-open",
diff --git a/xlators/performance/write-behind/src/write-behind.c b/xlators/performance/write-behind/src/write-behind.c
index 7f5719b1e48..bc59036ff88 100644
--- a/xlators/performance/write-behind/src/write-behind.c
+++ b/xlators/performance/write-behind/src/write-behind.c
@@ -169,6 +169,7 @@ typedef struct wb_request {
 
 typedef struct wb_conf {
         uint64_t         aggregate_size;
+        uint64_t         page_size;
         uint64_t         window_size;
         gf_boolean_t     flush_behind;
         gf_boolean_t     trickling_writes;
@@ -1207,18 +1208,21 @@ __wb_collapse_small_writes (wb_request_t *holder, wb_request_t *req)
         char          *ptr    = NULL;
         struct iobuf  *iobuf  = NULL;
         struct iobref *iobref = NULL;
+        struct wb_conf *conf = NULL;
         int            ret    = -1;
         ssize_t        required_size = 0;
         size_t         holder_len = 0;
         size_t         req_len = 0;
 
+        conf = req->wb_inode->this->private;
+
         if (!holder->iobref) {
                 holder_len = iov_length (holder->stub->args.vector,
                                          holder->stub->args.count);
                 req_len = iov_length (req->stub->args.vector,
                                       req->stub->args.count);
 
-                required_size = max ((THIS->ctx->page_size),
+                required_size = max ((conf->page_size),
                                      (holder_len + req_len));
                 iobuf = iobuf_get2 (req->wb_inode->this->ctx->iobuf_pool,
                                     required_size);
@@ -1281,7 +1285,6 @@ __wb_preprocess_winds (wb_inode_t *wb_inode)
 	wb_request_t *holder          = NULL;
 	wb_conf_t    *conf            = NULL;
         int           ret             = 0;
-	ssize_t       page_size       = 0;
 
 	/* With asynchronous IO from a VM guest (as a file), there
 	   can be two sequential writes happening in two regions
@@ -1292,7 +1295,6 @@ __wb_preprocess_winds (wb_inode_t *wb_inode)
 	   through the interleaved ops
 	*/
 
-	page_size = wb_inode->this->ctx->page_size;
 	conf = wb_inode->this->private;
 
         list_for_each_entry_safe (req, tmp, &wb_inode->todo, todo) {
@@ -1343,7 +1345,7 @@ __wb_preprocess_winds (wb_inode_t *wb_inode)
                         continue;
                 }
 
-		space_left = page_size - holder->write_size;
+		space_left = wb_inode->window_conf - holder->write_size;
 
 		if (space_left < req->write_size) {
 			holder->ordering.go = 1;
@@ -2471,6 +2473,9 @@ reconfigure (xlator_t *this, dict_t *options)
         GF_OPTION_RECONF ("cache-size", conf->window_size, options, size_uint64,
                           out);
 
+        GF_OPTION_RECONF ("cache-size", conf->page_size, options, size_uint64,
+                          out);
+
         GF_OPTION_RECONF ("flush-behind", conf->flush_behind, options, bool,
                           out);
 
@@ -2522,6 +2527,7 @@ init (xlator_t *this)
 
         /* configure 'option window-size <size>' */
         GF_OPTION_INIT ("cache-size", conf->window_size, size_uint64, out);
+        GF_OPTION_INIT ("cache-size", conf->page_size, size_uint64, out);
 
         if (!conf->window_size && conf->aggregate_size) {
                 gf_msg (this->name, GF_LOG_WARNING, 0,