From: Jason Gunthorpe <jgg@mellanox.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Philip Yang <Philip.Yang@amd.com>,
Ralph Campbell <rcampbell@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
Felix.Kuehling@amd.com, dri-devel@lists.freedesktop.org,
linux-mm@kvack.org, Jerome Glisse <jglisse@redhat.com>,
amd-gfx@lists.freedesktop.org
Subject: Re: [PATCH hmm 5/6] mm/hmm: remove the CONFIG_TRANSPARENT_HUGEPAGE #ifdef
Date: Mon, 23 Mar 2020 14:33:45 -0300 [thread overview]
Message-ID: <20200323173345.GB13183@mellanox.com> (raw)
In-Reply-To: <20200321084317.GE28695@lst.de>
On Sat, Mar 21, 2020 at 09:43:17AM +0100, Christoph Hellwig wrote:
> On Fri, Mar 20, 2020 at 01:49:04PM -0300, Jason Gunthorpe wrote:
> > From: Jason Gunthorpe <jgg@mellanox.com>
> >
> > This code can be compiled when CONFIG_TRANSPARENT_HUGEPAGE is off, so
> > remove the ifdef.
>
> It can compile, but will the compiler optimize it away?
Yes, the enclosing conditional:
if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
is statically false if !CONFIG_TRANSPARENT_HUGEPAGE
This is proven today, as the fallback stub is a function prototype
with no implementation:
-int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
- unsigned long end, uint64_t *pfns, pmd_t pmd);
If the compiler wasn't optimizing the above branch we'd get link
failures.
Jason
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next prev parent reply other threads:[~2020-03-24 8:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 16:48 [PATCH hmm 0/6] Small hmm_range_fault() cleanups Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 1/6] mm/hmm: remove pgmap checking for devmap pages Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 2/6] mm/hmm: return the fault type from hmm_pte_need_fault() Jason Gunthorpe
[not found] ` <20200321083726.GB28695@lst.de>
2020-03-23 20:14 ` Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 3/6] mm/hmm: remove unused code and tidy comments Jason Gunthorpe
2020-03-20 21:46 ` Ralph Campbell
2020-03-23 17:24 ` Jason Gunthorpe
[not found] ` <20200321083902.GC28695@lst.de>
2020-03-23 17:24 ` Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 4/6] mm/hmm: remove HMM_FAULT_SNAPSHOT Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 5/6] mm/hmm: remove the CONFIG_TRANSPARENT_HUGEPAGE #ifdef Jason Gunthorpe
[not found] ` <20200321084317.GE28695@lst.de>
2020-03-23 17:33 ` Jason Gunthorpe [this message]
2020-03-20 16:49 ` [PATCH hmm 6/6] mm/hmm: use device_private_entry_to_pfn() Jason Gunthorpe
[not found] ` <20200321084347.GF28695@lst.de>
2020-03-23 17:44 ` Jason Gunthorpe
2020-03-20 18:51 ` [PATCH hmm 0/6] Small hmm_range_fault() cleanups Ralph Campbell
2020-03-20 18:55 ` Jason Gunthorpe
2020-03-20 21:47 ` Ralph Campbell
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