On 11/14/22 08:44, Baoquan He wrote:
> Hi,
>
> I reproduced the build failure according to lkp report and made a patch
> as below to fix it.
>
> From dae7dd9705015ce36db757e88c78802584f949b1 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@xxxxxxxxxx>
> Date: Sun, 13 Nov 2022 18:08:27 +0800
> Subject: [PATCH] percpu: adjust the value of PERCPU_DYNAMIC_EARLY_SIZE
> Content-type: text/plain
>
> LKP reported a build failure as below on the patch "mm/slub, percpu:
> correct the calculation of early percpu allocation size"
Since I have that patch in slab.git exposed to -next, should I take this fix
too, to make things simpler? Dennis?
> ~~~~~~
> In file included from <command-line>:
> In function 'alloc_kmem_cache_cpus',
> inlined from 'kmem_cache_open' at mm/slub.c:4340:6:
>>> include/linux/compiler_types.h:357:45: error: call to '__compiletime_assert_474' declared with attribute error:
> BUILD_BUG_ON failed: PERCPU_DYNAMIC_EARLY_SIZE < NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu)
> 357 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> ~~~~~~
>
> From the kernel config file provided by LKP, the building was made on
> arm64 with below Kconfig item enabled:
>
> CONFIG_ZONE_DMA=y
> CONFIG_SLUB_CPU_PARTIAL=y
> CONFIG_DEBUG_LOCK_ALLOC=y
> CONFIG_SLUB_STATS=y
> CONFIG_ARM64_PAGE_SHIFT=16
> CONFIG_ARM64_64K_PAGES=y
>
> Then we will have:
> NR_KMALLOC_TYPES:4
> KMALLOC_SHIFT_HIGH:17
> sizeof(struct kmem_cache_cpu):184
>
> The product of them is 12512, which is bigger than PERCPU_DYNAMIC_EARLY_SIZE,
> 12K. Hence, the BUILD_BUG_ON in alloc_kmem_cache_cpus() is triggered.
>
> Earlier, in commit 099a19d91ca4 ("percpu: allow limited allocation
> before slab is online"), PERCPU_DYNAMIC_EARLY_SIZE was introduced and
> set to 12K which is equal to the then PERPCU_DYNAMIC_RESERVE.
> Later, in commit 1a4d76076cda ("percpu: implement asynchronous chunk
> population"), PERPCU_DYNAMIC_RESERVE was increased by 8K, while
> PERCPU_DYNAMIC_EARLY_SIZE was kept unchanged.
>
> So, here increase PERCPU_DYNAMIC_EARLY_SIZE by 8K too to accommodate to
> the slub's requirement.
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
> include/linux/percpu.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 70bc17db00a6..1338ea2aa720 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -41,7 +41,7 @@
> * for this. Keep PERCPU_DYNAMIC_RESERVE equal to or larger than
> * PERCPU_DYNAMIC_EARLY_SIZE.
> */
> -#define PERCPU_DYNAMIC_EARLY_SIZE (12 << 10)
> +#define PERCPU_DYNAMIC_EARLY_SIZE (20 << 10)
>
> /*
> * PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy
