linux-kernel - Re: [PATCH] slab: remove store

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Message-ID: <332fc776-65fa-eee6-e15d-2d872bd9d220@lca.pw>
Date:   Tue, 16 Apr 2019 11:34:49 -0400
From:   Qian Cai <cai@....pw>
To:     Vlastimil Babka <vbabka@...e.cz>, akpm@...ux-foundation.org
Cc:     luto@...nel.org, jpoimboe@...hat.com,
        sean.j.christopherson@...el.com, penberg@...nel.org,
        rientjes@...gle.com, tglx@...utronix.de, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] slab: remove store_stackinfo()



On 4/16/19 11:25 AM, Vlastimil Babka wrote:
> On 4/16/19 4:22 PM, Qian Cai wrote:
>> store_stackinfo() does not seem used in actual SLAB debugging.
>> Potentially, it could be added to check_poison_obj() to provide more
>> information, but this seems like an overkill due to the declining
>> popularity of the SLAB, so just remove it instead.
>>
>> Signed-off-by: Qian Cai <cai@....pw>
> 
> I've acked Thomas' version already which was narrower, but no objection
> to remove more stuff on top of that. Linus (and I later in another
> thread) already pointed out /proc/slab_allocators. It only takes a look
> at add_caller() there to not regret removing that one.

Well, with the 2 patches I sent a while back, /proc/slab_allocators is back to
life on all arches (arm64, powerpc, and x86) which provides a little information
that may still useful for debugging until SLAB is gone entirely.

# cat /proc/slab_allocators
xfs_ili: 92 kmem_zone_alloc+0x6c/0x100 [xfs]
xfs_ifork: 2539 kmem_zone_alloc+0x6c/0x100 [xfs]
xfs_log_ticket: 3 kmem_zone_alloc+0x6c/0x100 [xfs]
sd_ext_cdb: 2 mempool_alloc_slab+0x1c/0x30
ip_fib_trie: 7 fib_insert_alias+0x11a/0x2b0
ip_fib_alias: 9 fib_table_insert+0x16d/0x510
eventpoll_pwq: 5 ep_ptable_queue_proc+0x3f/0xc0
inotify_inode_mark: 8 __x64_sys_inotify_add_watch+0x225/0x340
khugepaged_mm_slot: 6 __khugepaged_enter+0x36/0x190
file_lock_ctx: 23 locks_get_lock_context+0xf2/0x180
fsnotify_mark_connector: 79 fsnotify_add_mark_locked+0x117/0x460
task_delay_info: 509 __delayacct_tsk_init+0x1e/0x50
sigqueue: 2 __sigqueue_alloc+0xa8/0x130
kernfs_iattrs_cache: 122 __kernfs_iattrs+0x5c/0xf0
kernfs_node_cache: 28234 __kernfs_new_node.constprop.6+0x65/0x200
buffer_head: 1 alloc_buffer_head+0x21/0x70
nsproxy: 4 create_new_namespaces+0x36/0x1c0
vm_area_struct: 17 vm_area_alloc+0x1e/0x60
anon_vma_chain: 16 __anon_vma_prepare+0x3d/0x160
anon_vma: 18 __anon_vma_prepare+0xd2/0x160
Acpi-Operand: 2931 acpi_ut_allocate_object_desc_dbg+0x3e/0x69
Acpi-Namespace: 1618 acpi_ns_create_node+0x37/0x46
numa_policy: 47 __mpol_dup+0x3c/0x170
kmemleak_scan_area: 994 kmemleak_scan_area+0xa0/0x1e0
kmemleak_object: 513426 create_object+0x48/0x2c0
trace_event_file: 1650 trace_create_new_event+0x22/0x90
ftrace_event_field: 3198 __trace_define_field+0x36/0xc0
vmap_area: 890 alloc_vmap_area+0xaf/0x880
vmap_area: 663 alloc_vmap_area+0x2a3/0x880
vmap_area: 6 pcpu_get_vm_areas+0x277/0xbe0
vmap_area: 1 pcpu_get_vm_areas+0x689/0xbe0
vmap_area: 1 vmalloc_init+0x23d/0x26e
debug_objects_cache: 15917 __debug_object_init+0x444/0x4e0
debug_objects_cache: 999 debug_objects_mem_init+0x7b/0x5a2
page->ptl: 1526 ptlock_alloc+0x1e/0x40