内核启动时间信息打印

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一 串口打印

1 借助串口助手

2 dmesg自带时间

root@xboard:~# dmesg
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
[    0.000000] Linux version 5.4.70-00016-gdd67dc4a0c6b (ub-1001@ub1001-Vostro-3890) (gcc version 9.2.0 (GCC)) #46 SMP PREEMPT Mon Dec 4 15:41:16 CST 2023
[    0.000000] Machine model: NXP i.MX8MM SMARC 2.0 Computer-on-Module
[    0.000000] efi: Getting EFI parameters from FDT:
[    0.000000] efi: UEFI not found.
[    0.000000] Reserved memory: created CMA memory pool at 0x0000000078000000, size 640 MiB
[    0.000000] OF: reserved mem: initialized node linux,cma, compatible id shared-dma-pool
[    0.000000] NUMA: No NUMA configuration found
[    0.000000] NUMA: Faking a node at [mem 0x0000000040000000-0x00000000bdffffff]
[    0.000000] NUMA: NODE_DATA [mem 0xbdbdc500-0xbdbddfff]
[    0.000000] Zone ranges:
[    0.000000]   DMA32    [mem 0x0000000040000000-0x00000000bdffffff]
[    0.000000]   Normal   empty
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000040000000-0x00000000b7ffffff]
[    0.000000]   node   0: [mem 0x00000000b8400000-0x00000000bdffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000bdffffff]
[    0.000000] On node 0 totalpages: 515072
[    0.000000]   DMA32 zone: 8064 pages used for memmap
[    0.000000]   DMA32 zone: 0 pages reserved
[    0.000000]   DMA32 zone: 515072 pages, LIFO batch:63
[    0.000000] psci: probing for conduit method from DT.
[    0.000000] psci: PSCIv1.1 detected in firmware.
[    0.000000] psci: Using standard PSCI v0.2 function IDs
[    0.000000] psci: Trusted OS migration not required
[    0.000000] psci: SMC Calling Convention v1.1
[    0.000000] percpu: Embedded 24 pages/cpu s58904 r8192 d31208 u98304
[    0.000000] pcpu-alloc: s58904 r8192 d31208 u98304 alloc=24*4096
[    0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 
[    0.000000] Detected VIPT I-cache on CPU0
[    0.000000] CPU features: detected: ARM erratum 845719
[    0.000000] CPU features: detected: GIC system register CPU interface
[    0.000000] Speculative Store Bypass Disable mitigation not required
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 507008
[    0.000000] Policy zone: DMA32
[    0.000000] Kernel command line: console=ttymxc1,115200 root=/dev/mmcblk1p2 rootwait rw loglevel=5 fbcon=logo-pos:center
[    0.000000] Dentry cache hash table entries: 262144 (order: 9, 2097152 bytes, linear)
[    0.000000] Inode-cache hash table entries: 131072 (order: 8, 1048576 bytes, linear)
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 1333432K/2060288K available (18172K kernel code, 1494K rwdata, 7220K rodata, 2944K init, 1049K bss, 71496K reserved, 655360K cma-reserved)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[    0.000000] rcu: Preemptible hierarchical RCU implementation.
[    0.000000] rcu:     RCU restricting CPUs from NR_CPUS=256 to nr_cpu_ids=4.
[    0.000000]  Tasks RCU enabled.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[    0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=4
[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[    0.000000] GICv3: GIC: Using split EOI/Deactivate mode
[    0.000000] GICv3: 128 SPIs implemented
[    0.000000] GICv3: 0 Extended SPIs implemented
[    0.000000] GICv3: Distributor has no Range Selector support
[    0.000000] GICv3: 16 PPIs implemented
[    0.000000] GICv3: no VLPI support, no direct LPI support
[    0.000000] GICv3: CPU0: found redistributor 0 region 0:0x0000000038880000
[    0.000000] ITS: No ITS available, not enabling LPIs
[    0.000000] random: get_random_bytes called from start_kernel+0x2b8/0x44c with crng_init=0
[    0.000000] arch_timer: cp15 timer(s) running at 8.00MHz (phys).
[    0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x1d854df40, max_idle_ns: 440795202120 ns
[    0.000003] sched_clock: 56 bits at 8MHz, resolution 125ns, wraps every 2199023255500ns
[    0.000380] Console: colour dummy device 80x25
[    0.000447] Calibrating delay loop (skipped), value calculated using timer frequency.. 16.00 BogoMIPS (lpj=32000)
[    0.000454] pid_max: default: 32768 minimum: 301
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