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SubjectRe: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of kmalloc
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On 10/30/22 20:23, John Thomson wrote:
> On Tue, 13 Sep 2022, at 06:54, Feng Tang wrote:
>> kmalloc's API family is critical for mm, with one nature that it will
>> round up the request size to a fixed one (mostly power of 2). Say
>> when user requests memory for '2^n + 1' bytes, actually 2^(n+1) bytes
>> could be allocated, so in worst case, there is around 50% memory
>> space waste.
>
>
> I have a ralink mt7621 router running Openwrt, using the mips ZBOOT kernel, and appear to have bisected
> a very-nearly-clean kernel v6.1rc-2 boot issue to this commit.
> I have 3 commits atop 6.1-rc2: fix a ZBOOT compile error, use the Openwrt LZMA options,
> and enable DEBUG_ZBOOT for my platform. I am compiling my kernel within the Openwrt build system.
> No guarantees this is not due to something I am doing wrong, but any insight would be greatly appreciated.
>
>
> On UART, No indication of the (once extracted) kernel booting:
>
> transfer started ......................................... transfer ok, time=2.01s
> setting up elf image... OK
> jumping to kernel code
> zimage at: 80BA4100 810D4720
> Uncompressing Linux at load address 80001000
> Copy device tree to address 80B96EE0
> Now, booting the kernel...

It's weird that the commit would cause no output so early, SLUB code is
run only later.

> Nothing follows
>
> 6edf2576a6cc ("mm/slub: enable debugging memory wasting of kmalloc") reverted, normal boot:
> transfer started ......................................... transfer ok, time=2.01s
> setting up elf image... OK
> jumping to kernel code
> zimage at: 80BA4100 810D47A4
> Uncompressing Linux at load address 80001000
> Copy device tree to address 80B96EE0
> Now, booting the kernel...
>
> [ 0.000000] Linux version 6.1.0-rc2 (john@john) (mipsel-openwrt-linux-musl-gcc (OpenWrt GCC 11.3.0 r19724+16-1521d5f453) 11.3.0, GNU ld (GNU Binutils) 2.37) #0 SMP Fri Oct 28 03:48:10 2022
> [ 0.000000] SoC Type: MediaTek MT7621 ver:1 eco:3
> [ 0.000000] printk: bootconsole [early0] enabled
> [ 0.000000] CPU0 revision is: 0001992f (MIPS 1004Kc)
> [ 0.000000] MIPS: machine is MikroTik RouterBOARD 760iGS
> [ 0.000000] Initrd not found or empty - disabling initrd
> [ 0.000000] VPE topology {2,2} total 4
> [ 0.000000] Primary instruction cache 32kB, VIPT, 4-way, linesize 32 bytes.
> [ 0.000000] Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
> [ 0.000000] MIPS secondary cache 256kB, 8-way, linesize 32 bytes.
> [ 0.000000] Zone ranges:
> [ 0.000000] Normal [mem 0x0000000000000000-0x000000000fffffff]
> [ 0.000000] HighMem empty
> [ 0.000000] Movable zone start for each node
> [ 0.000000] Early memory node ranges
> [ 0.000000] node 0: [mem 0x0000000000000000-0x000000000fffffff]
> [ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000000fffffff]
> [ 0.000000] percpu: Embedded 11 pages/cpu s16064 r8192 d20800 u45056
> [ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 64960
> [ 0.000000] Kernel command line: console=ttyS0,115200 rootfstype=squashfs,jffs2
> [ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes, linear)
> [ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
> [ 0.000000] Writing ErrCtl register=00019146
> [ 0.000000] Readback ErrCtl register=00019146
> [ 0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
> [ 0.000000] Memory: 246220K/262144K available (7455K kernel code, 628K rwdata, 1308K rodata, 3524K init, 245K bss, 15924K reserved, 0K cma-reserved, 0K highmem)
> [ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
> [ 0.000000] rcu: Hierarchical RCU implementation.
>
>
> boot continues as expected
>
>
> possibly relevant config options:
> grep -E '(SLUB|SLAB)' .config
> # SLAB allocator options
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> CONFIG_SLAB_MERGE_DEFAULT=y
> # CONFIG_SLAB_FREELIST_RANDOM is not set
> # CONFIG_SLAB_FREELIST_HARDENED is not set
> # CONFIG_SLUB_STATS is not set
> CONFIG_SLUB_CPU_PARTIAL=y
> # end of SLAB allocator options
> # CONFIG_SLUB_DEBUG is not set

Also not having CONFIG_SLUB_DEBUG enabled means most of the code the
patch/commit touches is not even active.
Could this be some miscompile or code layout change exposing some
different bug, hmm.
Is it any different if you do enable CONFIG_SLUB_DEBUG ?
Or change to CONFIG_SLAB? (that would be really weird if not)

>
> With this commit reverted: cpuinfo and meminfo
>
> system type : MediaTek MT7621 ver:1 eco:3
> machine : MikroTik RouterBOARD 760iGS
> processor : 0
> cpu model : MIPS 1004Kc V2.15
> BogoMIPS : 586.13
> wait instruction : yes
> microsecond timers : yes
> tlb_entries : 32
> extra interrupt vector : yes
> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
> isa : mips1 mips2 mips32r1 mips32r2
> ASEs implemented : mips16 dsp mt
> Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit cdmm perf
> shadow register sets : 1
> kscratch registers : 0
> package : 0
> core : 0
> VPE : 0
> VCED exceptions : not available
> VCEI exceptions : not available
>
> processor : 1
> cpu model : MIPS 1004Kc V2.15
> BogoMIPS : 586.13
> wait instruction : yes
> microsecond timers : yes
> tlb_entries : 32
> extra interrupt vector : yes
> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
> isa : mips1 mips2 mips32r1 mips32r2
> ASEs implemented : mips16 dsp mt
> Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit cdmm perf
> shadow register sets : 1
> kscratch registers : 0
> package : 0
> core : 0
> VPE : 1
> VCED exceptions : not available
> VCEI exceptions : not available
>
> processor : 2
> cpu model : MIPS 1004Kc V2.15
> BogoMIPS : 586.13
> wait instruction : yes
> microsecond timers : yes
> tlb_entries : 32
> extra interrupt vector : yes
> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
> isa : mips1 mips2 mips32r1 mips32r2
> ASEs implemented : mips16 dsp mt
> Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit cdmm perf
> shadow register sets : 1
> kscratch registers : 0
> package : 0
> core : 1
> VPE : 0
> VCED exceptions : not available
> VCEI exceptions : not available
>
> processor : 3
> cpu model : MIPS 1004Kc V2.15
> BogoMIPS : 586.13
> wait instruction : yes
> microsecond timers : yes
> tlb_entries : 32
> extra interrupt vector : yes
> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
> isa : mips1 mips2 mips32r1 mips32r2
> ASEs implemented : mips16 dsp mt
> Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit cdmm perf
> shadow register sets : 1
> kscratch registers : 0
> package : 0
> core : 1
> VPE : 1
> VCED exceptions : not available
> VCEI exceptions : not available
>
> MemTotal: 249744 kB
> MemFree: 211088 kB
> MemAvailable: 187364 kB
> Buffers: 0 kB
> Cached: 8824 kB
> SwapCached: 0 kB
> Active: 1104 kB
> Inactive: 8860 kB
> Active(anon): 1104 kB
> Inactive(anon): 8860 kB
> Active(file): 0 kB
> Inactive(file): 0 kB
> Unevictable: 0 kB
> Mlocked: 0 kB
> HighTotal: 0 kB
> HighFree: 0 kB
> LowTotal: 249744 kB
> LowFree: 211088 kB
> SwapTotal: 0 kB
> SwapFree: 0 kB
> Dirty: 0 kB
> Writeback: 0 kB
> AnonPages: 1192 kB
> Mapped: 2092 kB
> Shmem: 8824 kB
> KReclaimable: 1704 kB
> Slab: 9372 kB
> SReclaimable: 1704 kB
> SUnreclaim: 7668 kB
> KernelStack: 592 kB
> PageTables: 264 kB
> SecPageTables: 0 kB
> NFS_Unstable: 0 kB
> Bounce: 0 kB
> WritebackTmp: 0 kB
> CommitLimit: 124872 kB
> Committed_AS: 14676 kB
> VmallocTotal: 1040376 kB
> VmallocUsed: 2652 kB
> VmallocChunk: 0 kB
> Percpu: 272 kB
>
>
> Cheers,
>

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