gem5: benchmark hdf5 stats

Author: cirosantilli

README.adoc

@@ -202,6 +202,8 @@ The link:build[] script is just a lightweight wrapper that calls the smaller bui
 ./build --dry-run
 ....
 
+see also: <<dry-run>>.
+
 When you reach difficulties, QEMU makes it possible to easily GDB step debug the Linux kernel source code, see: xref:gdb[xrefstyle=full].
 
 ===== Your first kernel module hack
@@ -254,6 +256,8 @@ You can see that `./build` does that as well, by running:
 ./build --dry-run
 ....
 
+See also: <<dry-run>>.
+
 `--eval-after` is optional: you could just type `insmod hello.ko` in the terminal, but this makes it run automatically at the end of boot, and then drops you into a shell.
 
 If the guest and host are the same arch, typically x86_64, you can speed up boot further with <<kvm>>:
@@ -531,6 +535,7 @@ Read the following sections for further introductory material:
 * <<introduction-to-qemu>>
 * <<introduction-to-buildroot>>
 
+[[dry-run]]
 === Dry run to get commands for your project
 
 One of the major features of this repository is that we try to support the `--dry-run` option really well for all scripts.
@@ -11879,7 +11884,6 @@ To use that file, first rebuild `m5ops.out` with the m5ops instructions enabled
 ....
 ./build-userland \
   --arch aarch64 \
-  --ccflags='-DLKMC_M5OPS_ENABLE=1' \
   --force-rebuild \
   userland/c/m5ops.c \
 ;
@@ -12180,7 +12184,19 @@ as explained in:
 gem5.opt --stats-help
 ....
 
-TODO what is the advantage? The generated file for `--stats-file h5://stats.h5?desc=False` in LKMC f42c525d7973d70f4c836d2169cc2bd2893b4197 gem5 5af26353b532d7b5988cf0f6f3d0fbc5087dd1df was 946K, so much larger than the text version!
+This is not exposed in LKMC f42c525d7973d70f4c836d2169cc2bd2893b4197 however, you just have to <<dry-run,hack the gem5 CLI for now>>.
+
+TODO what is the advantage? The generated file for `--stats-file h5://stats.h5?desc=False` in LKMC f42c525d7973d70f4c836d2169cc2bd2893b4197 gem5 5af26353b532d7b5988cf0f6f3d0fbc5087dd1df for a single dump was 946K, so much larger than the text version seen at <<gem5-m5out-stats-txt-file>> which was only 59KB max!
+
+We then try to see if it is any better when you have a bunch of dump events:
+
+....
+./run --arch aarch64 --emulator gem5 --userland userland/c/m5ops.c --userland-args 'd 1000'
+....
+
+and there yes, we see that the file size fell from 39MB on `stats.txt` to 3.2MB on `stats.m5`, so the increase observed previously was just due to some initial size overhead.
+
+We also note however that the stat dump made the such a simulation that just loops and dumps considerably slower, from 3s to 15s on <<p51>>. Fascinating, we are definitely not disk bound there.
 
 ===== gem5 only dump selected stats
 

common.py

@@ -239,6 +239,8 @@ def __init__(
 Bash equivalents even for actions taken directly in Python without shelling out.
 
 mkdir are generally omitted since those are obvious
+
+See also: https://cirosantilli.com/linux-kernel-module-cheat#dry-run
 '''
         )
         self.add_argument(

path_properties.py

@@ -649,6 +649,7 @@ def get(path):
                         'file_write_read.c': {'baremetal': False},
                         'getchar.c': {'interactive': True},
                         'malloc_max.c': {'disrupts_system': True},
+                        'm5ops.c': {'allowed_emulators': {'gem5'}},
                         'return1.c': {'exit_status': 1},
                         'return2.c': {'exit_status': 2},
                     }
@@ -669,6 +670,7 @@ def get(path):
                             },
                         ),
                         'count.cpp': {'more_than_1s': True},
+                        'm5ops.cpp': {'allowed_emulators': {'gem5'}},
                         'parallel_sort.cpp': {'minimum_gcc_version': (9, 0, 0)},
                         'sleep_for.cpp': {
                             'more_than_1s': True,

userland/c/m5ops.c

@@ -1,34 +1,42 @@
 /* https://cirosantilli.com/linux-kernel-module-cheat#m5ops-instructions */
 
-#include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 
+#define LKMC_M5OPS_ENABLE 1
 #include <lkmc/m5ops.h>
 
 int main(int argc, char **argv) {
     char action;
+    unsigned long long loops;
+
     if (argc > 1) {
         action = argv[1][0];
     } else {
         action = 'e';
     }
-    switch (action) {
-        case 'c':
-            LKMC_M5OPS_CHECKPOINT;
-            break;
-        case 'd':
-            LKMC_M5OPS_DUMPSTATS;
-            break;
-        case 'e':
-            LKMC_M5OPS_EXIT;
-            break;
-        case 'f':
-            LKMC_M5OPS_FAIL_1;
-            break;
-        case 'r':
-            LKMC_M5OPS_RESETSTATS;
-            break;
+    if (argc > 2) {
+        loops = strtoull(argv[2], NULL, 0);
+    } else {
+        loops = 1;
+    }
+    for (unsigned long long i = 0; i < loops; i++) {
+        switch (action) {
+            case 'c':
+                LKMC_M5OPS_CHECKPOINT;
+                break;
+            case 'd':
+                LKMC_M5OPS_DUMPSTATS;
+                break;
+            case 'e':
+                LKMC_M5OPS_EXIT;
+                break;
+            case 'f':
+                LKMC_M5OPS_FAIL_1;
+                break;
+            case 'r':
+                LKMC_M5OPS_RESETSTATS;
+                break;
+        }
     }
     return EXIT_SUCCESS;
 }

userland/cpp/m5ops.cpp

@@ -1,5 +1,6 @@
 /* https://cirosantilli.com/linux-kernel-module-cheat#m5ops-instructions */
 
+#define LKMC_M5OPS_ENABLE 1
 #include <lkmc/m5ops.h>
 
 int main(int argc, char **argv) {