Back-end devices: In -S mode, limit the number of workitems so that no more than 2GB of host memory is required per backend device

docs/changes.txt

@@ -19,7 +19,7 @@
 ## Technical
 ##
 
-- Backend Devices: Reduce maximum workitems limited derived from available host memory down from to 8GB to 4GB per backend device
+- Back-end devices: In -S mode, limit the number of workitems so that no more than 2GB of host memory is required per backend device
 - Makefile: Added wildcard include src/modules/module_*.mk directive so that plugin developers can add 3rd party libraries for their plugins
 - Rejects: Disabled checking of the minimum and maximum length of the password candidate in attack-mode 9 because they are incompatible
 - POCL: Added a workaround for an issue in POCL that uses a quote character as part of the path itself given to a path for the -I option

src/backend.c

@@ -14546,11 +14546,19 @@ int backend_session_begin (hashcat_ctx_t *hashcat_ctx)
     // In theory this check could be disabled if we check if total video RAM < total host RAM,
     // but at this point of initialization phase we don't have this information available.
 
-    // We need to hard-code some value, let's assume that (in 2021) the host has at least 4GB ram per active GPU
+    // We need to hard-code some value, let's assume that (in 2021) the host has at least 8GB ram per active GPU
 
-    const u64 SIZE_4GB = 4ULL * 1024 * 1024 * 1024;
+    const u64 SIZE_8GB = 8ULL * 1024 * 1024 * 1024;
 
-    u64 accel_limit = SIZE_4GB;
+    u64 accel_limit = SIZE_8GB;
+
+    // in slow candidate mode we need to keep the buffers on the host alive
+    // a high accel value doesn't help much here anyway
+
+    if (user_options->slow_candidates == true)
+    {
+      accel_limit /= 4;
+    }
 
     // this is device_processors * kernel_threads