Re: [PATCH v2 6/6] slab, documentation: add description of debugfs files for SLUB caches

[Mike Rapoport]

On Wed, Mar 02, 2022 at 06:31:22PM +0100, Vlastimil Babka wrote:
> From: Oliver Glitta <glittao@xxxxxxxxx>
> 
> Add description of debugfs files alloc_traces and free_traces
> to SLUB cache documentation.
> 
> [ vbabka@xxxxxxx: some rewording ]
> 
> Signed-off-by: Oliver Glitta <glittao@xxxxxxxxx>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: linux-doc@xxxxxxxxxxxxxxx

Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>

> ---
>  Documentation/vm/slub.rst | 64 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
> 
> diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
> index d3028554b1e9..43063ade737a 100644
> --- a/Documentation/vm/slub.rst
> +++ b/Documentation/vm/slub.rst
> @@ -384,5 +384,69 @@ c) Execute ``slabinfo-gnuplot.sh`` in '-t' mode, passing all of the
>        40,60`` range will plot only samples collected between 40th and
>        60th seconds).
>  
> +
> +DebugFS files for SLUB
> +======================
> +
> +For more information about current state of SLUB caches with the user tracking
> +debug option enabled, debugfs files are available, typically under
> +/sys/kernel/debug/slab/<cache>/ (created only for caches with enabled user
> +tracking). There are 2 types of these files with the following debug
> +information:
> +
> +1. alloc_traces::
> +
> +    Prints information about unique allocation traces of the currently
> +    allocated objects. The output is sorted by frequency of each trace.
> +
> +    Information in the output:
> +    Number of objects, allocating function, minimal/average/maximal jiffies since alloc,
> +    pid range of the allocating processes, cpu mask of allocating cpus, and stack trace.
> +
> +    Example:::
> +
> +    1085 populate_error_injection_list+0x97/0x110 age=166678/166680/166682 pid=1 cpus=1::
> +	__slab_alloc+0x6d/0x90
> +	kmem_cache_alloc_trace+0x2eb/0x300
> +	populate_error_injection_list+0x97/0x110
> +	init_error_injection+0x1b/0x71
> +	do_one_initcall+0x5f/0x2d0
> +	kernel_init_freeable+0x26f/0x2d7
> +	kernel_init+0xe/0x118
> +	ret_from_fork+0x22/0x30
> +
> +
> +2. free_traces::
> +
> +    Prints information about unique freeing traces of the currently allocated
> +    objects. The freeing traces thus come from the previous life-cycle of the
> +    objects and are reported as not available for objects allocated for the first
> +    time. The output is sorted by frequency of each trace.
> +
> +    Information in the output:
> +    Number of objects, freeing function, minimal/average/maximal jiffies since free,
> +    pid range of the freeing processes, cpu mask of freeing cpus, and stack trace.
> +
> +    Example:::
> +
> +    1980 <not-available> age=4294912290 pid=0 cpus=0
> +    51 acpi_ut_update_ref_count+0x6a6/0x782 age=236886/237027/237772 pid=1 cpus=1
> +	kfree+0x2db/0x420
> +	acpi_ut_update_ref_count+0x6a6/0x782
> +	acpi_ut_update_object_reference+0x1ad/0x234
> +	acpi_ut_remove_reference+0x7d/0x84
> +	acpi_rs_get_prt_method_data+0x97/0xd6
> +	acpi_get_irq_routing_table+0x82/0xc4
> +	acpi_pci_irq_find_prt_entry+0x8e/0x2e0
> +	acpi_pci_irq_lookup+0x3a/0x1e0
> +	acpi_pci_irq_enable+0x77/0x240
> +	pcibios_enable_device+0x39/0x40
> +	do_pci_enable_device.part.0+0x5d/0xe0
> +	pci_enable_device_flags+0xfc/0x120
> +	pci_enable_device+0x13/0x20
> +	virtio_pci_probe+0x9e/0x170
> +	local_pci_probe+0x48/0x80
> +	pci_device_probe+0x105/0x1c0
> +
>  Christoph Lameter, May 30, 2007
>  Sergey Senozhatsky, October 23, 2015
> -- 
> 2.35.1
> 

-- 
Sincerely yours,
Mike.