DAOS-18193 ec: just for test

src/container/srv_target.c

@@ -433,7 +433,24 @@ cont_child_aggregate(struct ds_cont_child *cont, cont_aggregate_cb_t agg_cb,
 	if (!param->ap_vos_agg)
 		vos_cont_set_mod_bound(cont->sc_hdl, epoch_range.epr_hi);
 
-	if (dss_xstream_is_busy())
+	/*
+	 * Force-merge coalesces small contiguous records into large physical
+	 * extents to defragment the VOS tree. It's normally skipped for this
+	 * tail (non-snapshot) range under load to avoid relocation IO.
+	 *
+	 * For EC objects this coalescing is the ONLY way the data shards get
+	 * defragmented: the client can't recompute parity for partial-stripe
+	 * writes, so small writes land as many tiny records that only VOS
+	 * aggregation can merge. Unlike replicated objects, this range is
+	 * already capped to the EC aggregation epoch boundary (see
+	 * adjust_upper_bound()), so keeping force-merge enabled here can never
+	 * merge/relocate epochs whose parity isn't yet consistent - degraded
+	 * reads and rebuild always reconstruct identical bytes, i.e. no data
+	 * corruption. Retain it for the EC VOS-agg pass so partial-stripe EC
+	 * data doesn't stay fragmented (slow reads/rebuild) under sustained
+	 * load. Reversible via DAOS_EC_AGG_FORCE_MERGE=0.
+	 */
+	if (dss_xstream_is_busy() && !(param->ap_vos_agg && ec_agg_force_merge && !ec_agg_disabled))
 		flags &= ~VOS_AGG_FL_FORCE_MERGE;
 	rc = agg_cb(cont, &epoch_range, flags, param);
 out:

src/include/daos_srv/pool.h

@@ -415,6 +415,7 @@ int
 	    ds_pool_rebuild_stop(uuid_t pool_uuid, uint32_t force, struct rsvc_hint *hint);
 
 extern bool ec_agg_disabled;
+extern bool ec_agg_force_merge;
 
 int dsc_pool_open(uuid_t pool_uuid, uuid_t pool_hdl_uuid,
 		       unsigned int flags, const char *grp,

src/pool/srv.c

@@ -1,6 +1,6 @@
 /**
  * (C) Copyright 2016-2024 Intel Corporation.
- * (C) Copyright 2025 Hewlett Packard Enterprise Development LP
+ * (C) Copyright 2025-2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -22,6 +22,13 @@
 #include "srv_layout.h"
 
 bool		ec_agg_disabled;
+/*
+ * Keep VOS aggregation's force-merge (record coalescing) enabled for EC objects
+ * even when the target xstream is busy. For EC, coalescing the data shards is the
+ * only way partial-stripe writes get defragmented, and it is always bounded to the
+ * EC aggregation epoch boundary, so it cannot merge parity-inconsistent epochs.
+ */
+bool            ec_agg_force_merge = true;
 uint32_t        pw_rf = -1; /* pool wise redundancy factor */
 uint32_t        ps_cache_intvl = 2;  /* pool space cache expiration time, in seconds */
 #define PW_RF_DEFAULT (2)
@@ -73,6 +80,11 @@ init(void)
 	if (unlikely(ec_agg_disabled))
 		D_WARN("EC aggregation is disabled.\n");
 
+	ec_agg_force_merge = true;
+	d_getenv_bool("DAOS_EC_AGG_FORCE_MERGE", &ec_agg_force_merge);
+	if (!ec_agg_force_merge)
+		D_WARN("EC aggregation force-merge (coalescing under load) is disabled.\n");
+
 	pw_rf = -1;
 	if (!check_pool_redundancy_factor("DAOS_POOL_RF"))
 		pw_rf = PW_RF_DEFAULT;