fixup! :Introduce optimistic fast path for engine_rd

Signed-off-by: Michal Mielewczyk <[email protected]>
Open-CAS · Sep 10, 2024 · 0ed191f · 0ed191f
1 parent 4caf2f3
commit 0ed191f
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Showing 3 changed files with 68 additions and 50 deletions.
diff --git a/src/engine/engine_rd.c b/src/engine/engine_rd.c
@@ -259,7 +259,7 @@ int ocf_read_generic(struct ocf_request *req)
 	return 0;
 }
 
-bool ocf_read_generic_fast(struct ocf_request *req)
+int ocf_read_generic_try_fast(struct ocf_request *req)
 {
 	struct ocf_alock *c = ocf_cache_line_concurrency(req->cache);
 
@@ -277,6 +277,8 @@ bool ocf_read_generic_fast(struct ocf_request *req)
 	if (ocf_engine_is_mapped(req) && ocf_engine_is_hit(req) &&
 			ocf_cl_lock_line_fast(c, req, OCF_READ) == OCF_LOCK_ACQUIRED) {
 
+		OCF_DEBUG_RQ(req, "Submit read generic fast");
+
 		ocf_req_get(req);
 		ocf_engine_set_hot(req);
 		ocf_hb_req_prot_unlock_rd(req);
@@ -289,14 +291,13 @@ bool ocf_read_generic_fast(struct ocf_request *req)
 
 		ocf_read_generic_submit_hit(req);
 
-		ocf_req_get(req);
-		ocf_read_generic_submit_hit(req);
 		/* Update statistics */
 		ocf_engine_update_request_stats(req);
 		ocf_engine_update_block_stats(req);
-		return true;
+		return OCF_FAST_PATH_YES;
 	} else {
 		ocf_hb_req_prot_unlock_rd(req);
-		return false;
+		OCF_DEBUG_RQ(req, "Failed to read generic fast");
+		return OCF_FAST_PATH_NO;
 	}
 }
diff --git a/src/engine/engine_rd.h b/src/engine/engine_rd.h
@@ -9,6 +9,6 @@
 int ocf_read_generic(struct ocf_request *req);
 
 void ocf_read_generic_submit_hit(struct ocf_request *req);
-bool ocf_read_generic_fast(struct ocf_request *req);
+int ocf_read_generic_try_fast(struct ocf_request *req);
 
 #endif /* ENGINE_RD_H_ */
diff --git a/src/ocf_core.c b/src/ocf_core.c
@@ -221,62 +221,79 @@ static void ocf_req_complete(struct ocf_request *req, int error)
 	ocf_io_put(&req->ioi.io);
 }
 
-static int ocf_core_submit_io_fast(struct ocf_io *io, struct ocf_request *req,
-		ocf_core_t core, ocf_cache_t cache)
+static inline int _ocf_core_submit_io_fast_rd_generic(struct ocf_io *io,
+		struct ocf_request *req)
 {
-	ocf_req_cache_mode_t original_cache_mode;
-	int fast;
-
-	if (req->d2c) {
-		return -OCF_ERR_IO;
-	}
+	int res;
 
 	switch (req->cache_mode) {
-	case ocf_req_cache_mode_wt:
-	case ocf_req_cache_mode_wa:
-	case ocf_req_cache_mode_wi:
-		if (io->dir == OCF_READ && req->core_line_count <= MAX_FAST_PATH_CACHE_LINES) {
-			if (ocf_read_generic_fast(req))
-				return 0;
-			ocf_req_clear_map(req);
-		}
-		break;
-
-	case ocf_req_cache_mode_wb:
-	case ocf_req_cache_mode_wo:
-		if (io->dir == OCF_READ && req->core_line_count <= MAX_FAST_PATH_CACHE_LINES)
-			return ocf_read_generic_fast(req) ? 0 : -OCF_ERR_IO;
-		break;
-	default:
-		break;
+		case ocf_req_cache_mode_wt:
+		case ocf_req_cache_mode_wa:
+		case ocf_req_cache_mode_wi:
+		case ocf_req_cache_mode_wb:
+		case ocf_req_cache_mode_wo:
+			res = ocf_read_generic_try_fast(req);
+			break;
+		default:
+			break;
 	}
 
-	original_cache_mode = req->cache_mode;
+	if (res == OCF_FAST_PATH_NO)
+		ocf_req_clear_map(req);
+
+	return res;
+}
 
+static inline ocf_req_cache_mode_t _ocf_core_req_resolve_fast_mode(
+		ocf_cache_t cache, struct ocf_request *req)
+{
 	switch (req->cache_mode) {
-	case ocf_req_cache_mode_pt:
-		return -OCF_ERR_IO;
-	case ocf_req_cache_mode_wb:
-	case ocf_req_cache_mode_wo:
-		if (io->dir == OCF_WRITE)
-			req->cache_mode = ocf_req_cache_mode_fast;
-		break;
-	default:
-		if (cache->use_submit_io_fast)
+		case ocf_req_cache_mode_wb:
+		case ocf_req_cache_mode_wo:
+			return ocf_req_cache_mode_fast;
+		default:
 			break;
+	}
 
-		if (io->dir == OCF_WRITE)
-			return -OCF_ERR_IO;
+	if (!cache->use_submit_io_fast)
+		return ocf_req_cache_mode_max;
 
-		req->cache_mode = ocf_req_cache_mode_fast;
+	return ocf_req_cache_mode_fast;
+}
+
+static int ocf_core_submit_io_fast(struct ocf_io *io, struct ocf_request *req,
+		ocf_cache_t cache)
+{
+	ocf_req_cache_mode_t original_mode, resolved_mode;
+	int ret;
+
+	if (req->d2c) {
+		return OCF_FAST_PATH_NO;
 	}
 
-	fast = ocf_engine_hndl_fast_req(req);
-	if (fast != OCF_FAST_PATH_NO)
-		return 0;
+	if (req->cache_mode == ocf_req_cache_mode_pt)
+		return OCF_FAST_PATH_NO;
+
+	/* If a read request isn't too big for a lookup in submission context,
+	   check it is a read-hit and if cache line lock could be acquired
+	   without waiting. If so, submit immediately */
+	if (req->rw == OCF_READ) {
+		if (req->core_line_count <= MAX_FAST_PATH_CACHE_LINES)
+			return _ocf_core_submit_io_fast_rd_generic(io, req);
+	}
+
+	resolved_mode = _ocf_core_req_resolve_fast_mode(cache, req);
+	if (resolved_mode == ocf_req_cache_mode_max)
+		return OCF_FAST_PATH_NO;
+
+	original_mode = req->cache_mode;
+	req->cache_mode = resolved_mode;
+
+	ret = ocf_engine_hndl_fast_req(req);
+	if (ret == OCF_FAST_PATH_NO)
+		req->cache_mode = original_mode;
 
-	req->cache_mode = original_cache_mode;
-	return -OCF_ERR_IO;
+	return ret;
 }
 
 static void ocf_core_volume_submit_io(struct ocf_io *io)
@@ -321,7 +338,7 @@ static void ocf_core_volume_submit_io(struct ocf_io *io)
 	/* Prevent race condition */
 	ocf_req_get(req);
 
-	if (!ocf_core_submit_io_fast(io, req, core, cache)) {
+	if (ocf_core_submit_io_fast(io, req, cache) == OCF_FAST_PATH_YES) {
 		ocf_core_seq_cutoff_update(core, req);
 		ocf_req_put(req);
 		return;