zswap.zpool: z3fold is now deprecated and zbud could have the same faith in the near future, better handle this change

include/swap-default.conf

@@ -17,7 +17,7 @@
 zswap_enabled=1
 zswap_compressor=zstd     # lzo lz4 zstd lzo-rle lz4hc
 zswap_max_pool_percent=25 # 1-99
-zswap_zpool=z3fold        # zbud z3fold (note z3fold requires kernel 4.8+)
+zswap_zpool=zsmalloc        # zbud z3fold (note z3fold requires kernel 4.8+, deprecated since 6.12) zsmalloc
 
 ################################################################################
 # ZRam

include/systemd-swap.service

@@ -1,7 +1,7 @@
 [Unit]
 Description=Manage swap spaces on zram, files and partitions.
-[email protected]
-[email protected]
+[email protected] [email protected] [email protected]
+[email protected] [email protected] [email protected]
 
 [Service]
 Type=notify

man/swap.conf.5

@@ -49,7 +49,7 @@ and
 Percentage of ram that can be compressed.
 .I
 .IP zswap_zpool=
-Set wich compressed memory pool to use, if unsure use z3fold.
+Set wich compressed memory pool to use, if unsure use zsmalloc.
 .PP
 The following options are available in the "zram" section:
 .I

src/systemd-swap.py

@@ -37,7 +37,7 @@ def get_mem_stats(fields: List[str]) -> Dict[str, int]:
                 stats[key] = int(items[1]) * 1024
             if not fields:
                 break
-    assert len(fields) == 0
+    assert len(fields) <= 1
     return stats
 
 
@@ -57,8 +57,8 @@ def get_mem_stats(fields: List[str]) -> Dict[str, int]:
 )
 WORK_DIR = "/run/systemd/swap"
 LOCK_STARTED = f"{WORK_DIR}/.started"
-ZSWAP_M = "/sys/module/zswap"
-ZSWAP_M_P = "/sys/module/zswap/parameters"
+MODULE_PATH = "/sys/module"
+ZSWAP_M_P = f"{MODULE_PATH}/zswap/parameters"
 KMAJOR, KMINOR = [int(v) for v in os.uname().release.split(".")[0:2]]
 IS_DEBUG = False
 sigterm_event = threading.Event()
@@ -423,15 +423,22 @@ def destroy_swapfile(self) -> None:
 
     @staticmethod
     def get_free_ram_perc() -> int:
-        ram_stats = get_mem_stats(["MemTotal", "MemFree"])
-        return round((ram_stats["MemFree"] * 100) / ram_stats["MemTotal"])
+        ram_stats = get_mem_stats(["MemTotal", "MemFree", "MemAvailable"])
+        if "MemAvailable" in ram_stats:
+            free_ram = ram_stats["MemAvailable"]
+        else:
+            free_ram = ram_stats["MemFree"]
+        return round((free_ram * 100) / ram_stats["MemTotal"])
 
     @staticmethod
     def get_free_swap_perc() -> int:
         swap_stats = get_mem_stats(["SwapTotal", "SwapFree"])
         # Minimum for total is 1 to prevent divide by zero.
         return round((swap_stats["SwapFree"] * 100) / max(swap_stats["SwapTotal"], 1))
 
+def module_loaded(module_name) -> bool:
+    return os.path.isdir(f"/sys/module/{module_name}")
+
 
 def debug(msg: str) -> None:
     if IS_DEBUG:
@@ -468,8 +475,11 @@ def relative_symlink(target: str, link_name: str) -> None:
 
 
 def write(data: str, file: str) -> None:
-    with open(file, "w") as f:
-        f.write(data)
+    try:
+        with open(file, "w") as f:
+            f.write(data)
+    except:
+        warn(f"Failed writing {data} to file {file}")
 
 
 def read(file: str) -> str:
@@ -625,8 +635,12 @@ def start_swapd() -> None:
 
     def start_zswap() -> None:
         systemd.daemon.notify("STATUS=Setting up Zswap...")
-        if not os.path.isdir(ZSWAP_M):
-            error("Zswap - not supported on current kernel")
+        info("Zswap: check module availability")
+        if module_loaded("zswap"):
+            info("Zswap: module loaded")
+        else:
+            error("Zswap: module not available")
+
         info("Zswap: backup current configuration: start")
         makedirs(f"{WORK_DIR}/zswap")
         for file in os.listdir(ZSWAP_M_P):
@@ -640,19 +654,30 @@ def start_zswap() -> None:
             f'{config.get("zswap_max_pool_percent")}, Zpool: '
             f'{config.get("zswap_zpool")}'
         )
+
+        zpool_allocator = config.get("zswap_zpool")
+        if (zpool_allocator != "zsmalloc") and (not module_loaded(zpool_allocator)):
+            warn(f"Zswap: Desired Zpool allocator {zpool_allocator} not available")
+            if zswap_parameters[f"{ZSWAP_M_P}/zpool"]:
+                zpool_allocator = zswap_parameters[f"{ZSWAP_M_P}/zpool"]
+                warn(f"Zswap: Keeping current {zpool_allocator}")
+            else:
+                zpool_allocator = "zsmalloc"
+                warn("Zswap: Defaulting to zsmalloc")
+
         write(config.get("zswap_enabled"), f"{ZSWAP_M_P}/enabled")
         write(config.get("zswap_compressor"), f"{ZSWAP_M_P}/compressor")
         write(config.get("zswap_max_pool_percent"), f"{ZSWAP_M_P}/max_pool_percent")
-        write(config.get("zswap_zpool"), f"{ZSWAP_M_P}/zpool")
+        write(zpool_allocator, f"{ZSWAP_M_P}/zpool")
         info("Zswap: set new parameters: complete")
 
     def start_zram() -> None:
         systemd.daemon.notify("STATUS=Setting up Zram...")
         info("Zram: check module availability")
-        if not os.path.isdir("/sys/module/zram"):
-            error("Zram: module not availible")
+        if module_loaded("zram"):
+            info("Zram: module loaded")
         else:
-            info("Zram: module found!")
+            error("Zram: module not available")
 
         def zram_init() -> None:
             info("Zram: trying to initialize free device")