Hi,
Our x86 system has crashed because oom.
We found task_struct slabs ate much memory.
And we analyzed the core file just as follows.
Why the page's inuse is 0 but the slab can't be released back to buddy system ?
The memory allocator is slub.
crash> kmem -s task_struct
CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE //**Slabs is much larger than alloctated object counts**
ffff88081e007500 task_struct 6528 4639 229775 45955 32k
crash> p *(struct kmem_cache *)0xffff88081e007500
$54 = {
cpu_slab = 0x14e10,
flags = 1074003968,
min_partial = 6,
size = 6528,
objsize = 6528,
offset = 0,
cpu_partial = 2,
oo = {
x = 196613
},
max = {
x = 196613
},
min = {
x = 65537
},
allocflags = 16384,
refcount = 1,
ctor = 0x0,
inuse = 6528,
align = 16,
reserved = 0,
name = 0xffff88081e000920 "task_struct",
list = {
next = 0xffff88081e007468,
prev = 0xffff88081e007668
},
kobj = {
name = 0xffff880810faf9b0 ":t-0006528",
entry = {
next = 0xffff88081e007480,
prev = 0xffff88081e007680
},
parent = 0xffff880810fc0258,
kset = 0xffff880810fc0240,
ktype = 0xffffffff81847040 <slab_ktype>,
sd = 0xffff880c2542c3f0,
kref = {
refcount = {
counter = 1
}
},
state_initialized = 1,
state_in_sysfs = 1,
state_add_uevent_sent = 1,
state_remove_uevent_sent = 0,
uevent_suppress = 0
},
remote_node_defrag_ratio = 1000,
node = {0xffff88081e001440, 0xffff880c2e800440, 0x0, 0x0, 0x0, 0x0,
crash> p *(struct kmem_cache_node *)0xffff88081e001440
$55 = {
list_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 254283560,
tickets = {
head = 3880,
tail = 3880
}
}
}
}
}
},
nr_partial = 45287,
partial = {
next = 0xffffea0001396c20,
prev = 0xffffea00202a8220
},
nr_slabs = {
counter = 45829
},
total_objects = {
counter = 229125
},
full = {
next = 0xffff88081e001470,
prev = 0xffff88081e001470
}
}
crash> p *((struct page *)((char *)0xffffea0001396c20-32))
$57 = {
flags = 9007199254757504,
mapping = 0x0,
{
{
index = 18446612136879672448,
freelist = 0xffff8801101f4c80
},
{
counters = 4295294976,
{
{
_mapcount = {
counter = 327680
},
{
inuse = 0, //##Here we found the slab page's inuse is 0.##
objects = 5,
frozen = 0
}
},
_count = {
counter = 1
}
}
}
},
{
lru = {
next = 0xffffea00055dde20,
prev = 0xffffea0002e0be20
},
{
next = 0xffffea00055dde20,
pages = 48283168,
pobjects = -5632
}
},
{
private = 18446612167177303296,
ptl = {
{
rlock = {
raw_lock = {
{
head_tail = 503346432,
tickets = {
head = 29952,
tail = 7680
}
}
}
}
}
},
slab = 0xffff88081e007500,
first_page = 0xffff88081e007500
}
}
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