use higher send thresholds

src/StackExchange.Redis/SocketManager.cs

 using System;
-using System.Collections.Generic;
-using System.IO;
 using System.IO.Pipelines;
 using System.Net;
 using System.Net.Sockets;
 using System.Threading;
-using System.Threading.Tasks;
 using Pipelines.Sockets.Unofficial;
 
 namespace StackExchange.Redis
@@ -76,10 +73,18 @@ private SocketManager(string name, bool useHighPrioritySocketThreads, int worker
             if (string.IsNullOrWhiteSpace(name)) name = GetType().Name;
             Name = name;
 
-            const long Receive_PauseWriterThreshold = 4L * 1024 * 1024 * 1024; // let's give it up to 4GiB of buffer for now
-            const long Receive_ResumeWriterThreshold = 3L * 1024 * 1024 * 1024;
+            const long Receive_PauseWriterThreshold = 4L * 1024 * 1024 * 1024; // receive: let's give it up to 4GiB of buffer for now
+            const long Receive_ResumeWriterThreshold = 3L * 1024 * 1024 * 1024; // (large replies get crazy big)
 
             var defaultPipeOptions = PipeOptions.Default;
+
+            long Send_PauseWriterThreshold = Math.Max(
+                512 * 1024,// send: let's give it up to 0.5MiB
+                defaultPipeOptions.PauseWriterThreshold); // or the default, whichever is bigger
+            long Send_ResumeWriterThreshold = Math.Max(
+                Send_PauseWriterThreshold / 2,
+                defaultPipeOptions.ResumeWriterThreshold);
+
             _schedulerPool = new DedicatedThreadPoolPipeScheduler(name + ":IO",
                 workerCount: workerCount,
                 priority: useHighPrioritySocketThreads ? ThreadPriority.AboveNormal : ThreadPriority.Normal);
@@ -87,8 +92,8 @@ private SocketManager(string name, bool useHighPrioritySocketThreads, int worker
                 pool: defaultPipeOptions.Pool,
                 readerScheduler: _schedulerPool,
                 writerScheduler: _schedulerPool,
-                pauseWriterThreshold: defaultPipeOptions.PauseWriterThreshold,
-                resumeWriterThreshold: defaultPipeOptions.ResumeWriterThreshold,
+                pauseWriterThreshold: Send_PauseWriterThreshold,
+                resumeWriterThreshold: Send_ResumeWriterThreshold,
                 minimumSegmentSize: Math.Max(defaultPipeOptions.MinimumSegmentSize, MINIMUM_SEGMENT_SIZE),
                 useSynchronizationContext: false);
             ReceivePipeOptions = new PipeOptions(