OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> writes:
> Dave Anderson <anderson@xxxxxxxxxx> writes:
>
>> Here's an example. I ran your patch on a live 3.10-based kernel, and
>> see these counts on the xfs-based caches:
>
> [...]
>
>> ffff880035d54300 xfs_efd_item 400 0 300 15 8k
>> ffff880035d54200 xfs_da_state 480 0 272 8 16k
>> ffff880035d54100 xfs_btree_cur 208 0 312 8 8k
>> ffff880035d54000 xfs_log_ticket 184 3 682 31 4k
>
> [...]
>
>> xfs_efd_item 180 300 400 20 2 : tunables 0 0 0 : slabdata 15 15 0
>> xfs_da_state 272 272 480 34 4 : tunables 0 0 0 : slabdata 8 8 0
>> xfs_btree_cur 312 312 208 39 2 : tunables 0 0 0 : slabdata 8 8 0
>> xfs_log_ticket 682 682 184 22 1 : tunables 0 0 0 : slabdata 31 31 0
>> crash>
>>
>> which show 180, 272, 312 and 682 active counts.
>>
>> Can you explain the discrepancy?
>
> The active counts means just a non percpu slab, not the allocated.
> The algorithm of active counts is
OK. More simpler proof, the following is enough to convince you?
The test code is here. 1) Make own slab cache as "test_memory". 2) And
allocate 3 objects on local cpu, 3) then one is freed on local cpu, one
is freed on remote cpu, and one is not freed.
struct test_memory {
unsigned long dummy;
};
struct kmem_cache *t_cachep;
struct test_memory *t_m[3];
int t_cpu;
static void t_free(void *info)
{
kmem_cache_free(t_cachep, info);
}
static int t_init(void)
{
unsigned int cpu;
t_cachep = kmem_cache_create("test_memory", sizeof(*t_m),
0, SLAB_NOLEAKTRACE /* prevent merge */,
NULL);
if (!t_cachep)
return -ENOMEM;
cpu = get_cpu();
t_cpu = cpu;
t_m[cpu] = kmem_cache_alloc(t_cachep, GFP_KERNEL); /* local */
t_m[!cpu] = kmem_cache_alloc(t_cachep, GFP_KERNEL); /* remote */
t_m[2] = kmem_cache_alloc(t_cachep, GFP_KERNEL); /* pin */
kmem_cache_free(t_cachep, t_m[cpu]); /* local */
smp_call_function_single(!cpu, t_free, t_m[!cpu], 1); /* remote */
put_cpu();
return 0;
}
module_init(t_init);
And I took vmcore after run above, then run crash for same vmcore
with/without my patch.
[Without my patch]
crash> p t_cpu
t_cpu = $1 = 1
crash> p t_m
t_m = $2 =
{0xffff880119b65008, 0xffff880119b65000, 0xffff880119b65010}
crash> kmem -S test_memory
CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE
ffff88011aec3b40 test_memory 8 2 512 1 4k
CPU 0 KMEM_CACHE_CPU:
ffff88011bbdc200
CPU 0 SLAB:
(empty)
CPU 0 PARTIAL:
(empty)
CPU 1 KMEM_CACHE_CPU:
ffff88011bddc200
CPU 1 SLAB:
SLAB MEMORY NODE TOTAL ALLOCATED FREE
ffffea000466d940 ffff880119b65000 0 512 2 510
FREE / [ALLOCATED]
ffff880119b65000 (cpu 1 cache)
[ffff880119b65008]
[ffff880119b65010]
ffff880119b65018 (cpu 1 cache)
ffff880119b65020 (cpu 1 cache)
[...]
local cpu free is showed as ffff880119b65000 - OK
remote cpu free is showed as [ffff880119b65008] - FAIL
pin is showed as [ffff880119b65010] - OK
[With my patch]
crash> kmem -S test_memory
CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE
ffff88011aec3b40 test_memory 8 1 512 1 4k
CPU 0 KMEM_CACHE_CPU:
ffff88011bbdc200
CPU 0 SLAB:
(empty)
CPU 0 PARTIAL:
(empty)
CPU 1 KMEM_CACHE_CPU:
ffff88011bddc200
CPU 1 SLAB:
SLAB MEMORY NODE TOTAL ALLOCATED FREE
ffffea000466d940 ffff880119b65000 0 512 1 511
FREE / [ALLOCATED]
ffff880119b65000 (cpu 1 cache)
ffff880119b65008 (cpu 1 cache)
[ffff880119b65010]
ffff880119b65018 (cpu 1 cache)
ffff880119b65020 (cpu 1 cache)
[...]
local cpu free is showed as ffff880119b65000 - OK
remote cpu free is showed as ffff880119b65008 - OK
pin is showed as [ffff880119b65010] - OK
Thanks.
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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