From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Baoquan He <bhe@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, hch@lst.de, cl@linux.com,
John.p.donnelly@oracle.com, kexec@lists.infradead.org,
stable@vger.kernel.org, Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone
Date: Mon, 13 Dec 2021 13:43:19 +0000 [thread overview]
Message-ID: <20211213134319.GA997240@odroid> (raw)
In-Reply-To: <20211213122712.23805-6-bhe@redhat.com>
Hello Baoquan. I have a question on your code.
On Mon, Dec 13, 2021 at 08:27:12PM +0800, Baoquan He wrote:
> Dma-kmalloc will be created as long as CONFIG_ZONE_DMA is enabled.
> However, it will fail if DMA zone has no managed pages. The failure
> can be seen in kdump kernel of x86_64 as below:
>
> CPU: 0 PID: 65 Comm: kworker/u2:1 Not tainted 5.14.0-rc2+ #9
> Hardware name: Intel Corporation SandyBridge Platform/To be filled by O.E.M., BIOS RMLSDP.86I.R2.28.D690.1306271008 06/27/2013
> Workqueue: events_unbound async_run_entry_fn
> Call Trace:
> dump_stack_lvl+0x57/0x72
> warn_alloc.cold+0x72/0xd6
> __alloc_pages_slowpath.constprop.0+0xf56/0xf70
> __alloc_pages+0x23b/0x2b0
> allocate_slab+0x406/0x630
> ___slab_alloc+0x4b1/0x7e0
> ? sr_probe+0x200/0x600
> ? lock_acquire+0xc4/0x2e0
> ? fs_reclaim_acquire+0x4d/0xe0
> ? lock_is_held_type+0xa7/0x120
> ? sr_probe+0x200/0x600
> ? __slab_alloc+0x67/0x90
> __slab_alloc+0x67/0x90
> ? sr_probe+0x200/0x600
> ? sr_probe+0x200/0x600
> kmem_cache_alloc_trace+0x259/0x270
> sr_probe+0x200/0x600
> ......
> bus_probe_device+0x9f/0xb0
> device_add+0x3d2/0x970
> ......
> __scsi_add_device+0xea/0x100
> ata_scsi_scan_host+0x97/0x1d0
> async_run_entry_fn+0x30/0x130
> process_one_work+0x2b0/0x5c0
> worker_thread+0x55/0x3c0
> ? process_one_work+0x5c0/0x5c0
> kthread+0x149/0x170
> ? set_kthread_struct+0x40/0x40
> ret_from_fork+0x22/0x30
> Mem-Info:
> ......
>
> The above failure happened when calling kmalloc() to allocate buffer with
> GFP_DMA. It requests to allocate slab page from DMA zone while no managed
> pages in there.
> sr_probe()
> --> get_capabilities()
> --> buffer = kmalloc(512, GFP_KERNEL | GFP_DMA);
>
> The DMA zone should be checked if it has managed pages, then try to create
> dma-kmalloc.
>
What is problem here?
The slab allocator requested buddy allocator with GFP_DMA,
and then buddy allocator failed to allocate page in DMA zone because
there was no page in DMA zone. and then the buddy allocator called warn_alloc
because it failed at allocating page.
Looking at warn, I don't understand what the problem is.
> ---
> mm/slab_common.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index e5d080a93009..ae4ef0f8903a 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -878,6 +878,9 @@ void __init create_kmalloc_caches(slab_flags_t flags)
> {
> int i;
> enum kmalloc_cache_type type;
> +#ifdef CONFIG_ZONE_DMA
> + bool managed_dma;
> +#endif
>
> /*
> * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined
> @@ -905,10 +908,16 @@ void __init create_kmalloc_caches(slab_flags_t flags)
> slab_state = UP;
>
> #ifdef CONFIG_ZONE_DMA
> + managed_dma = has_managed_dma();
> +
> for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
> struct kmem_cache *s = kmalloc_caches[KMALLOC_NORMAL][i];
>
> if (s) {
> + if (!managed_dma) {
> + kmalloc_caches[KMALLOC_DMA][i] = kmalloc_caches[KMALLOC_NORMAL][i];
> + continue;
> + }
This code is copying normal kmalloc caches to DMA kmalloc caches.
With this code, the kmalloc() with GFP_DMA will succeed even if allocated
memory is not actually from DMA zone. Is that really what you want?
Maybe the function get_capabilities() want to allocate memory
even if it's not from DMA zone, but other callers will not expect that.
Thanks,
Hyeonggon.
> kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
> kmalloc_info[i].name[KMALLOC_DMA],
> kmalloc_info[i].size,
> --
> 2.17.2
>
>
next prev parent reply other threads:[~2021-12-13 13:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211213122712.23805-1-bhe@redhat.com>
2021-12-13 12:27 ` [PATCH v3 3/5] mm_zone: add function to check if managed dma zone exists Baoquan He
2021-12-13 14:22 ` john.p.donnelly
2021-12-16 10:52 ` David Hildenbrand
2021-12-13 12:27 ` [PATCH v3 4/5] dma/pool: create dma atomic pool only if dma zone has managed pages Baoquan He
2021-12-13 14:23 ` john.p.donnelly
2021-12-13 12:27 ` [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone Baoquan He
2021-12-13 13:43 ` Hyeonggon Yoo [this message]
2021-12-14 5:32 ` Baoquan He
2021-12-14 10:09 ` Vlastimil Babka
2021-12-14 10:28 ` Christoph Lameter
2021-12-15 4:48 ` Hyeonggon Yoo
2021-12-15 7:03 ` Hyeonggon Yoo
2021-12-15 7:27 ` Christoph Hellwig
2021-12-15 10:34 ` Vlastimil Babka
2021-12-15 11:51 ` David Laight
2021-12-15 13:41 ` Baoquan He
2021-12-17 11:38 ` Hyeonggon Yoo
2021-12-20 7:32 ` Baoquan He
2022-01-07 11:56 ` Hyeonggon Yoo
2021-12-15 14:42 ` Baoquan He
2021-12-15 10:08 ` Baoquan He
2021-12-17 11:38 ` Hyeonggon Yoo
2021-12-21 8:56 ` Christoph Hellwig
2021-12-22 12:37 ` Hyeonggon Yoo
2021-12-23 8:52 ` Christoph Hellwig
2021-12-13 14:24 ` john.p.donnelly
2021-12-14 16:31 ` Christoph Hellwig
2021-12-14 17:07 ` john.p.donnelly
2021-12-15 7:27 ` Christoph Hellwig
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