Tidy up nano-sleep wait directives to an update.nim-function

nimbus/sync/beacon/worker/blocks_staged.nim

@@ -18,7 +18,7 @@ import
   ../worker_desc,
   ./blocks_staged/bodies,
   ./update/metrics,
-  "."/[blocks_unproc, db, helpers]
+  "."/[blocks_unproc, db, helpers, update]
 
 # ------------------------------------------------------------------------------
 # Private debugging & logging helpers
@@ -324,10 +324,7 @@ proc blocksStagedImport*(
       ctx.updateMetrics()
 
       # Allow pseudo/async thread switch.
-      try: await sleepAsync asyncThreadSwitchTimeSlot
-      except CancelledError: discard
-      if not ctx.daemon:
-        # Shutdown?
+      (await ctx.updateAsyncTasks()).isOkOr:
         maxImport = ctx.chain.latestNumber()
         break importLoop
 
@@ -349,9 +346,7 @@ proc blocksStagedImport*(
           break importLoop
 
         # Allow pseudo/async thread switch.
-        try: await sleepAsync asyncThreadSwitchTimeSlot
-        except CancelledError: discard
-        if not ctx.daemon:
+        (await ctx.updateAsyncTasks()).isOkOr:
           maxImport = ctx.chain.latestNumber()
           break importLoop
 

nimbus/sync/beacon/worker/update.nim

@@ -344,6 +344,26 @@ proc updateFinalBlockHeader*(
     # Update, so it can be followed nicely
     ctx.updateMetrics()
 
+
+proc updateAsyncTasks*(
+    ctx: BeaconCtxRef;
+      ): Future[Opt[void]] {.async: (raises: []).} =
+  ## Allow task switch by issuing a short sleep request. The `due` argument
+  ## allows to maintain a minimum time gap when invoking this function.
+  let start = Moment.now()
+  if ctx.pool.nextAsyncNanoSleep < start:
+
+    try: await sleepAsync asyncThreadSwitchTimeSlot
+    except CancelledError: discard
+
+    if ctx.daemon:
+      ctx.pool.nextAsyncNanoSleep = Moment.now() + asyncThreadSwitchGap
+      return ok()
+    # Shutdown?
+    return err()
+
+  return ok()
+
 # ------------------------------------------------------------------------------
 # End
 # ------------------------------------------------------------------------------

nimbus/sync/beacon/worker_config.nim

@@ -46,6 +46,11 @@ const
   asyncThreadSwitchTimeSlot* = chronos.nanoseconds(1)
     ## Nano-sleep to allows pseudo/async thread switch
 
+  asyncThreadSwitchGap* = chronos.milliseconds(300)
+    ## Controls nano-sleep tart switch density when using this in a loop (e.g.
+    ## for processing lists.) The constant requires a minimum time gap when
+    ## invoking a nano-sleep utility.
+
   # ----------------------
 
   nFetchHeadersRequest* = 1_024

nimbus/sync/beacon/worker_desc.nim

@@ -143,6 +143,7 @@ type
     hdrSync*: HeaderImportSync       ## Syncing by linked header chains
     blkSync*: BlocksImportSync       ## For importing/executing blocks
     nextMetricsUpdate*: Moment       ## For updating metrics
+    nextAsyncNanoSleep*: Moment      ## Use nano-sleeps for task switch
 
     # Blocks import/execution settings for importing with
     # `nBodiesBatch` blocks in each round (minimum value is