Re: [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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@xxxxxxxxxx>
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@xxxxxxxxxx/


No, I meant:

https://lore.kernel.org/all/20240327152332.950956-4-peterx@xxxxxxxxxx/

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@xxxxxxxxxx>

--
Cheers,

David / dhildenb





[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux