From: David Hildenbrand <david@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>,
akpm@linux-foundation.org, linux-mm@kvack.org, hughd@google.com,
hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com,
iii@linux.ibm.com, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org, Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages
Date: Wed, 10 Apr 2024 19:03:21 +0200 [thread overview]
Message-ID: <79051196-601a-406c-9572-033173848bfb@redhat.com> (raw)
In-Reply-To: <ZhbDoxxFAe0QQYz_@x1n>
On 10.04.24 18:51, Peter Xu wrote:
> On Wed, Apr 10, 2024 at 06:40:55PM +0200, David Hildenbrand wrote:
>> On 10.04.24 18:33, Peter Xu wrote:
>>> On Wed, Apr 10, 2024 at 06:12:34PM +0200, David Hildenbrand wrote:
>>>> On 10.04.24 18:07, Sumanth Korikkar wrote:
>>>>> On Wed, Apr 10, 2024 at 05:51:28PM +0200, David Hildenbrand wrote:
>>>>>> On 10.04.24 17:26, Sumanth Korikkar wrote:
>>>>>>> On Wed, Apr 10, 2024 at 02:34:35PM +0200, David Hildenbrand wrote:
>>>>>>>> On 09.04.24 17:54, Sumanth Korikkar wrote:
>>>>>>>>> In order to minimize code size (CONFIG_CC_OPTIMIZE_FOR_SIZE=y),
>>>>>>>>> compiler might choose to make a regular function call (out-of-line) for
>>>>>>>>> shmem_is_huge() instead of inlining it. When transparent hugepages are
>>>>>>>>> disabled (CONFIG_TRANSPARENT_HUGEPAGE=n), it can cause compilation
>>>>>>>>> error.
>>>>>>>>>
>>>>>>>>> mm/shmem.c: In function ‘shmem_getattr’:
>>>>>>>>> ./include/linux/huge_mm.h:383:27: note: in expansion of macro ‘BUILD_BUG’
>>>>>>>>> 383 | #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })
>>>>>>>>> | ^~~~~~~~~
>>>>>>>>> mm/shmem.c:1148:33: note: in expansion of macro ‘HPAGE_PMD_SIZE’
>>>>>>>>> 1148 | stat->blksize = HPAGE_PMD_SIZE;
>>>>>>>>>
>>>>>>>>> To prevent the possible error, always inline shmem_is_huge() when
>>>>>>>>> transparent hugepages are disabled.
>>>>>>>>>
>>>>>>>>
>>>>>>>> Do you know which commit introduced that?
>>>>>>> Hi David,
>>>>>>>
>>>>>>> Currently with CONFIG_CC_OPTIMIZE_FOR_SIZE=y and expirementing with
>>>>>>> -fPIC kernel compiler option, I could see this error on s390.
>>>>>>
>>>>>> Got it. I assume on Linus' tree, not mm/unstable?
>>>>>
>>>>> It's not yet upstream.
>>>>>>
>>>>>>>
>>>>>>> However, default kernel compiler options doesnt end up with the above
>>>>>>> pattern right now.
>>>>>>
>>>>>> Okay, just asking if this is related to recent HPAGE_PMD_SIZE changes:
>>>>>>
>>>>>> commit c1a1e497a3d5711dbf8fa6d7432d6b83ec18c26f
>>>>>> Author: Peter Xu <peterx@redhat.com>
>>>>>> Date: Wed Mar 27 11:23:22 2024 -0400
>>>>>>
>>>>>> mm: make HPAGE_PXD_* macros even if !THP
>>>>>>
>>>>>> Which is still in mm-unstable and not upstream.
>>>>>
>>>>> Not related to this commit. I tried on master branch.
>>>>
>>>> Thanks! Can you try with Peters patch? (ccing Peter)
>>>>
>>>> If I am not wrong, that should also resolve the issue you are seeing.
>>>
>>> David,
>>>
>>> Do you mean this one?
>>>
>>> https://lore.kernel.org/all/20240403013249.1418299-4-peterx@redhat.com/
>>>
>>
>> No, I meant:
>>
>> https://lore.kernel.org/all/20240327152332.950956-4-peterx@redhat.com/
>>
>> which removes the "#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })" that we
>> seem to trigger here.
>>
>>
>> ... but it's been a long day, so maybe I'm all wrong :)
>
> Ah.. So I thought it was one step further. :)
>
> Then that shouldn't be the case; it didn't remove it but defined properly
> with HPAGE_PMD_SHIFT:
>
> +#define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
>
> Now we even have that properly defined for HUGETLB_PAGE, while prior to
> that we should hit this issue easier (even with !THP+HUGETLB_PAGE).
Ah, now I spot
#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
:) sorry for the noise!
To the original patch here
Acked-by: David Hildenbrand <david@redhat.com>
--
Cheers,
David / dhildenb
prev parent reply other threads:[~2024-04-10 17:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 15:54 [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages Sumanth Korikkar
2024-04-10 12:34 ` David Hildenbrand
2024-04-10 15:26 ` Sumanth Korikkar
2024-04-10 15:51 ` David Hildenbrand
2024-04-10 16:07 ` Sumanth Korikkar
2024-04-10 16:12 ` David Hildenbrand
2024-04-10 16:33 ` Peter Xu
2024-04-10 16:40 ` David Hildenbrand
2024-04-10 16:51 ` Peter Xu
2024-04-10 17:03 ` David Hildenbrand [this message]
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