diff --git a/.github/workflows/daily.yml b/.github/workflows/daily.yml
index 028c44e0c..cfbf24f87 100644
--- a/.github/workflows/daily.yml
+++ b/.github/workflows/daily.yml
@@ -99,6 +99,23 @@ jobs:
         ./runtest-cluster --tls
         ./runtest-cluster
 
+  test-ubuntu-io-threads:
+    runs-on: ubuntu-latest
+    if: github.repository == 'redis/redis'
+    timeout-minutes: 14400
+    steps:
+    - uses: actions/checkout@v2
+    - name: make
+      run: |
+        make
+    - name: test
+      run: |
+        sudo apt-get install tcl8.5 tcl-tls
+        ./runtest --config io-threads 4 --config io-threads-do-reads yes --accurate --verbose --tags network
+    - name: cluster tests
+      run: |
+        ./runtest-cluster --config io-threads 4 --config io-threads-do-reads yes
+
   test-valgrind:
     runs-on: ubuntu-latest
     if: github.repository == 'redis/redis'
diff --git a/tests/instances.tcl b/tests/instances.tcl
index a9cc01008..18eb1a402 100644
--- a/tests/instances.tcl
+++ b/tests/instances.tcl
@@ -24,6 +24,7 @@ set ::simulate_error 0
 set ::failed 0
 set ::sentinel_instances {}
 set ::redis_instances {}
+set ::global_config {}
 set ::sentinel_base_port 20000
 set ::redis_base_port 30000
 set ::redis_port_count 1024
@@ -92,6 +93,9 @@ proc spawn_instance {type base_port count {conf {}}} {
         foreach directive $conf {
             puts $cfg $directive
         }
+        dict for {name val} $::global_config {
+            puts $cfg "$name $val"
+        }
         close $cfg
 
         # Finally exec it and remember the pid for later cleanup.
@@ -239,6 +243,10 @@ proc parse_options {} {
                 -certfile "$::tlsdir/client.crt" \
                 -keyfile "$::tlsdir/client.key"
             set ::tls 1
+        } elseif {$opt eq {--config}} {
+            set val2 [lindex $::argv [expr $j+2]]
+            dict set ::global_config $val $val2
+            incr j 2
         } elseif {$opt eq "--help"} {
             puts "--single <pattern>      Only runs tests specified by pattern."
             puts "--dont-clean            Keep log files on exit."
@@ -246,6 +254,7 @@ proc parse_options {} {
             puts "--fail                  Simulate a test failure."
             puts "--valgrind              Run with valgrind."
             puts "--tls                   Run tests in TLS mode."
+            puts "--config <k> <v>        Extra config argument(s)."
             puts "--help                  Shows this help."
             exit 0
         } else {
diff --git a/tests/integration/rdb.tcl b/tests/integration/rdb.tcl
index 99495b2b7..a89221197 100644
--- a/tests/integration/rdb.tcl
+++ b/tests/integration/rdb.tcl
@@ -1,3 +1,5 @@
+tags {"rdb"} {
+
 set server_path [tmpdir "server.rdb-encoding-test"]
 
 # Copy RDB with different encodings in server path
@@ -289,3 +291,5 @@ start_server {overrides {save ""}} {
     }
 }
 } ;# system_name
+
+} ;# tags
diff --git a/tests/integration/redis-benchmark.tcl b/tests/integration/redis-benchmark.tcl
index 5a4f09952..3684d7c3b 100644
--- a/tests/integration/redis-benchmark.tcl
+++ b/tests/integration/redis-benchmark.tcl
@@ -5,7 +5,7 @@ proc cmdstat {cmd} {
     return [cmdrstat $cmd r]
 }
 
-start_server {tags {"benchmark"}} {
+start_server {tags {"benchmark network"}} {
     start_server {} {
         set master_host [srv 0 host]
         set master_port [srv 0 port]
diff --git a/tests/integration/replication-4.tcl b/tests/integration/replication-4.tcl
index 8071c4f97..c867001b8 100644
--- a/tests/integration/replication-4.tcl
+++ b/tests/integration/replication-4.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"repl"}} {
+start_server {tags {"repl network"}} {
     start_server {} {
 
         set master [srv -1 client]
diff --git a/tests/integration/replication.tcl b/tests/integration/replication.tcl
index 6c437ba71..8d09c68c1 100644
--- a/tests/integration/replication.tcl
+++ b/tests/integration/replication.tcl
@@ -5,7 +5,7 @@ proc log_file_matches {log pattern} {
     string match $pattern $content
 }
 
-start_server {tags {"repl"}} {
+start_server {tags {"repl network"}} {
     set slave [srv 0 client]
     set slave_host [srv 0 host]
     set slave_port [srv 0 port]
diff --git a/tests/support/server.tcl b/tests/support/server.tcl
index 77ba31d84..0d36d46be 100644
--- a/tests/support/server.tcl
+++ b/tests/support/server.tcl
@@ -152,20 +152,48 @@ proc server_is_up {host port retrynum} {
     return 0
 }
 
+# Check if current ::tags match requested tags. If ::allowtags are used,
+# there must be some intersection. If ::denytags are used, no intersection
+# is allowed. Returns 1 if tags are acceptable or 0 otherwise, in which
+# case err_return names a return variable for the message to be logged.
+proc tags_acceptable {err_return} {
+    upvar $err_return err
+
+    # If tags are whitelisted, make sure there's match
+    if {[llength $::allowtags] > 0} {
+        set matched 0
+        foreach tag $::allowtags {
+            if {[lsearch $::tags $tag] >= 0} {
+                incr matched
+            }
+        }
+        if {$matched < 1} {
+            set err "Tag: none of the tags allowed"
+            return 0
+        }
+    }
+
+    foreach tag $::denytags {
+        if {[lsearch $::tags $tag] >= 0} {
+            set err "Tag: $tag denied"
+            return 0
+        }
+    }
+
+    return 1
+}
+
 # doesn't really belong here, but highly coupled to code in start_server
 proc tags {tags code} {
     # If we 'tags' contain multiple tags, quoted and seperated by spaces,
     # we want to get rid of the quotes in order to have a proper list
     set tags [string map { \" "" } $tags]
     set ::tags [concat $::tags $tags]
-    # We skip unwanted tags
-    foreach tag $::denytags {
-        if {[lsearch $::tags $tag] >= 0} {
-            incr ::num_aborted
-            send_data_packet $::test_server_fd ignore "Tag: $tag"
-            set ::tags [lrange $::tags 0 end-[llength $tags]]
-            return
-        }
+    if {![tags_acceptable err]} {
+        incr ::num_aborted
+        send_data_packet $::test_server_fd ignore $err
+        set ::tags [lrange $::tags 0 end-[llength $tags]]
+        return
     }
     uplevel 1 $code
     set ::tags [lrange $::tags 0 end-[llength $tags]]
@@ -267,13 +295,11 @@ proc start_server {options {code undefined}} {
     }
 
     # We skip unwanted tags
-    foreach tag $::denytags {
-        if {[lsearch $::tags $tag] >= 0} {
-            incr ::num_aborted
-            send_data_packet $::test_server_fd ignore "Tag: $tag"
-            set ::tags [lrange $::tags 0 end-[llength $tags]]
-            return
-        }
+    if {![tags_acceptable err]} {
+        incr ::num_aborted
+        send_data_packet $::test_server_fd ignore $err
+        set ::tags [lrange $::tags 0 end-[llength $tags]]
+        return
     }
 
     # If we are running against an external server, we just push the
diff --git a/tests/unit/limits.tcl b/tests/unit/limits.tcl
index 38ba76208..51122e8f5 100644
--- a/tests/unit/limits.tcl
+++ b/tests/unit/limits.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"limits"} overrides {maxclients 10}} {
+start_server {tags {"limits network"} overrides {maxclients 10}} {
     if {$::tls} {
         set expected_code "*I/O error*"
     } else {
diff --git a/tests/unit/pause.tcl b/tests/unit/pause.tcl
index 9f5cfd607..67b684d36 100644
--- a/tests/unit/pause.tcl
+++ b/tests/unit/pause.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"pause"}} {
+start_server {tags {"pause network"}} {
     test "Test read commands are not blocked by client pause" {
         r client PAUSE 100000000 WRITE
         set rd [redis_deferring_client]
diff --git a/tests/unit/protocol.tcl b/tests/unit/protocol.tcl
index 4dfdc6f59..442c23de6 100644
--- a/tests/unit/protocol.tcl
+++ b/tests/unit/protocol.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"protocol"}} {
+start_server {tags {"protocol network"}} {
     test "Handle an empty query" {
         reconnect
         r write "\r\n"
diff --git a/tests/unit/pubsub.tcl b/tests/unit/pubsub.tcl
index 9c7a43bf0..966565ae1 100644
--- a/tests/unit/pubsub.tcl
+++ b/tests/unit/pubsub.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"pubsub"}} {
+start_server {tags {"pubsub network"}} {
     proc __consume_subscribe_messages {client type channels} {
         set numsub -1
         set counts {}
diff --git a/tests/unit/scan.tcl b/tests/unit/scan.tcl
index 9f9ff4df2..3981a2234 100644
--- a/tests/unit/scan.tcl
+++ b/tests/unit/scan.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"scan"}} {
+start_server {tags {"scan network"}} {
     test "SCAN basic" {
         r flushdb
         r debug populate 1000
diff --git a/tests/unit/tracking.tcl b/tests/unit/tracking.tcl
index 88cf9dc42..7aaca47ca 100644
--- a/tests/unit/tracking.tcl
+++ b/tests/unit/tracking.tcl
@@ -1,4 +1,4 @@
-start_server {tags {"tracking"}} {
+start_server {tags {"tracking network"}} {
     # Create a deferred client we'll use to redirect invalidation
     # messages to.
     set rd_redirection [redis_deferring_client]
diff --git a/tests/unit/wait.tcl b/tests/unit/wait.tcl
index 0a4965c20..78c3d8202 100644
--- a/tests/unit/wait.tcl
+++ b/tests/unit/wait.tcl
@@ -1,6 +1,6 @@
 source tests/support/cli.tcl
 
-start_server {tags {"wait"}} {
+start_server {tags {"wait network"}} {
 start_server {} {
     set slave [srv 0 client]
     set slave_host [srv 0 host]