Linux kernel and system-level performance optimization for RK3326

Kernel config:
- SCHED_AUTOGROUP=n: Disable task auto-grouping (causes latency spikes)
- DRM_PANFROST=y (was m): Build GPU driver into kernel (faster probe)
- DRM_FBDEV_EMULATION=n: Remove legacy framebuffer overhead
- PROFILING=n: Disable kernel profiling (CPU overhead)
- MAGIC_SYSRQ=n: Remove debug code path
- PAGE_REPORTING=n: Disable page reporting overhead
- BTRFS_FS=n: Remove 300KB+ kernel bloat (unused)
- NTFS/NTFS3=n: Remove Windows FS support (unused)
- BRIDGE=n: Remove network bridging (unused)

Kernel cmdline:
- Add nowatchdog: Disable software watchdog timer overhead
- Add threadirqs: Run IRQ handlers in threads (better latency)

Sysctl tuning:
- vm.laptop_mode: 5→0 (was causing I/O batching latency spikes)
- vm.dirty_writeback_centisecs: 1500→500 (15s→5s, prevents frame stutters)
- vm.vfs_cache_pressure: 200→50 (stop aggressive cache eviction on 1GB RAM)
- vm.dirty_ratio: 5→10 (allow more dirty memory before sync)
- vm.dirty_background_ratio: 2→5 (less aggressive background writeback)

Systemd:
- journald: Set Storage=volatile (RAM-only, zero SD card writes)

projects/ArchR/devices/RK3326/linux/linux.aarch64.conf

@@ -205,7 +205,7 @@ CONFIG_USER_NS=y
 CONFIG_PID_NS=y
 CONFIG_NET_NS=y
 # CONFIG_CHECKPOINT_RESTORE is not set
-CONFIG_SCHED_AUTOGROUP=y
+# CONFIG_SCHED_AUTOGROUP is not set
 CONFIG_RELAY=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_INITRAMFS_SOURCE="@INITRAMFS_SOURCE@"
@@ -270,7 +270,7 @@ CONFIG_PERF_EVENTS=y
 # end of Kernel Performance Events And Counters
 
 CONFIG_SYSTEM_DATA_VERIFICATION=y
-CONFIG_PROFILING=y
+# CONFIG_PROFILING is not set
 
 #
 # Kexec and crash features
@@ -948,7 +948,7 @@ CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK=y
 CONFIG_SPLIT_PMD_PTLOCKS=y
 CONFIG_COMPACTION=y
 CONFIG_COMPACT_UNEVICTABLE_DEFAULT=1
-CONFIG_PAGE_REPORTING=y
+# CONFIG_PAGE_REPORTING is not set
 CONFIG_MIGRATION=y
 CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION=y
 CONFIG_ARCH_ENABLE_THP_MIGRATION=y
@@ -1355,7 +1355,7 @@ CONFIG_INET_SCTP_DIAG=m
 # CONFIG_ATM is not set
 # CONFIG_L2TP is not set
 CONFIG_STP=m
-CONFIG_BRIDGE=m
+# CONFIG_BRIDGE is not set
 CONFIG_BRIDGE_IGMP_SNOOPING=y
 # CONFIG_BRIDGE_VLAN_FILTERING is not set
 # CONFIG_BRIDGE_MRP is not set
@@ -3609,7 +3609,7 @@ CONFIG_DRM_KMS_HELPER=y
 # CONFIG_DRM_DEBUG_MODESET_LOCK is not set
 CONFIG_DRM_CLIENT_SELECTION=y
 CONFIG_DRM_CLIENT_SETUP=y
-CONFIG_DRM_FBDEV_EMULATION=y
+# CONFIG_DRM_FBDEV_EMULATION is not set
 CONFIG_DRM_FBDEV_OVERALLOC=200
 # CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is not set
 # CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
@@ -3831,7 +3831,7 @@ CONFIG_DRM_PANEL_MIPI_DBI=m
 # CONFIG_TINYDRM_ST7735R is not set
 # CONFIG_DRM_PL111 is not set
 # CONFIG_DRM_LIMA is not set
-CONFIG_DRM_PANFROST=m
+CONFIG_DRM_PANFROST=y
 # CONFIG_DRM_PANTHOR is not set
 # CONFIG_DRM_TIDSS is not set
 # CONFIG_DRM_GUD is not set
@@ -6009,12 +6009,7 @@ CONFIG_FS_MBCACHE=y
 # CONFIG_XFS_FS is not set
 # CONFIG_GFS2_FS is not set
 # CONFIG_OCFS2_FS is not set
-CONFIG_BTRFS_FS=y
-CONFIG_BTRFS_FS_POSIX_ACL=y
-# CONFIG_BTRFS_FS_RUN_SANITY_TESTS is not set
-# CONFIG_BTRFS_DEBUG is not set
-# CONFIG_BTRFS_ASSERT is not set
-# CONFIG_BTRFS_FS_REF_VERIFY is not set
+# CONFIG_BTRFS_FS is not set
 # CONFIG_NILFS2_FS is not set
 # CONFIG_F2FS_FS is not set
 # CONFIG_BCACHEFS_FS is not set
@@ -6073,11 +6068,8 @@ CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1"
 # CONFIG_FAT_DEFAULT_UTF8 is not set
 CONFIG_EXFAT_FS=m
 CONFIG_EXFAT_DEFAULT_IOCHARSET="utf8"
-CONFIG_NTFS3_FS=m
-# CONFIG_NTFS3_64BIT_CLUSTER is not set
-# CONFIG_NTFS3_LZX_XPRESS is not set
-# CONFIG_NTFS3_FS_POSIX_ACL is not set
-CONFIG_NTFS_FS=m
+# CONFIG_NTFS3_FS is not set
+# CONFIG_NTFS_FS is not set
 # end of DOS/FAT/EXFAT/NT Filesystems
 
 #
@@ -6739,10 +6731,7 @@ CONFIG_FRAME_POINTER=y
 #
 # Generic Kernel Debugging Instruments
 #
-CONFIG_MAGIC_SYSRQ=y
-CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE=0x1
-CONFIG_MAGIC_SYSRQ_SERIAL=y
-CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE=""
+# CONFIG_MAGIC_SYSRQ is not set
 CONFIG_DEBUG_FS=y
 CONFIG_DEBUG_FS_ALLOW_ALL=y
 # CONFIG_DEBUG_FS_DISALLOW_MOUNT is not set

projects/ArchR/devices/RK3326/options

@@ -36,7 +36,7 @@
     KERNEL_MAKE_EXTRACMD=" $(get_kernel_make_extracmd)"
 
   # Kernel cmdline
-    EXTRA_CMDLINE="quiet console=ttyS2,1500000 console=tty0 loglevel=0 vt.global_cursor_default=0 consoleblank=0 net.ifnames=0 systemd.show_status=false mitigations=off audit=0 loop.max_loop=16"
+    EXTRA_CMDLINE="quiet console=ttyS2,1500000 console=tty0 loglevel=0 vt.global_cursor_default=0 consoleblank=0 net.ifnames=0 systemd.show_status=false mitigations=off audit=0 nowatchdog threadirqs loop.max_loop=16"
 
   # Bootloader to use (syslinux / u-boot)
     BOOTLOADER="u-boot"

projects/ArchR/packages/sysutils/systemd/config/journald.conf.d/00-volatile.conf

@@ -0,0 +1,4 @@
+[Journal]
+Storage=volatile
+RuntimeMaxUse=16M
+RuntimeMaxFileSize=4M

projects/ArchR/packages/sysutils/systemd/config/sysctl.d/archr.conf

@@ -1,7 +1,7 @@
-vm.swappiness=1
 kernel.nmi_watchdog=0
-vm.laptop_mode=5
-vm.dirty_writeback_centisecs=1500
-vm.vfs_cache_pressure=200
-vm.dirty_ratio=5
-vm.dirty_background_ratio=2
+vm.swappiness=1
+vm.laptop_mode=0
+vm.dirty_writeback_centisecs=500
+vm.vfs_cache_pressure=50
+vm.dirty_ratio=10
+vm.dirty_background_ratio=5

projects/ArchR/packages/sysutils/systemd/package.mk

@@ -197,7 +197,8 @@ post_makeinstall_target() {
   safe_remove ${INSTALL}/usr/lib/systemd/system/systemd-time-wait-sync.service
   safe_remove ${INSTALL}/usr/lib/systemd/systemd-time-wait-sync
 
-  # tune journald.conf
+  # tune journald.conf - volatile storage (RAM only, no SD writes)
+  sed -e "s,^.*Storage=.*$,Storage=volatile,g" -i ${INSTALL}/etc/systemd/journald.conf
   sed -e "s,^.*Compress=.*$,Compress=no,g" -i ${INSTALL}/etc/systemd/journald.conf
   sed -e "s,^.*MaxFileSec=.*$,MaxFileSec=0,g" -i ${INSTALL}/etc/systemd/journald.conf
   sed -e "s,^.*MaxRetentionSec=.*$,MaxRetentionSec=0,g" -i ${INSTALL}/etc/systemd/journald.conf