From: David Hildenbrand <david@redhat.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>, linux-mm@kvack.org
Cc: justin.he@arm.com, catalin.marinas@arm.com,
akpm@linux-foundation.org, Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Michal Hocko <mhocko@suse.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
linux-riscv@lists.infradead.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V4 1/3] mm/sparsemem: Enable vmem_altmap support in vmemmap_populate_basepages()
Date: Mon, 6 Jul 2020 11:03:47 +0200 [thread overview]
Message-ID: <eeeb44f9-bc0a-2c3d-8e8f-7e3d9e066c7e@redhat.com> (raw)
In-Reply-To: <1594004178-8861-2-git-send-email-anshuman.khandual@arm.com>
> return 0;
> @@ -1505,7 +1505,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> int err;
>
> if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> - err = vmemmap_populate_basepages(start, end, node);
> + err = vmemmap_populate_basepages(start, end, node, NULL);
> else if (boot_cpu_has(X86_FEATURE_PSE))
> err = vmemmap_populate_hugepages(start, end, node, altmap);
> else if (altmap) {
It's somewhat weird that we don't allocate basepages from altmap on x86
(both for sub-sections and without PSE). I wonder if we can simply
unlock that with your change. Especially, also handle the
!X86_FEATURE_PSE case below properly with an altmap.
a) all hw with PMEM has PSE - except special QEMU setups, so nobody
cared to implement. For the sub-section special case, nobody cared about
a handfull of memmap not ending up on the altmap. (but it's still wasted
system memory IIRC).
b) the pagetable overhead for small pages is not-neglectable and might
result in similar issues as solved by the switch to altmap on very huge
PMEM (with small amount of system RAM).
I guess it is due to a).
[...]
>
> -pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node)
> +pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
> + struct vmem_altmap *altmap)
> {
> pte_t *pte = pte_offset_kernel(pmd, addr);
> if (pte_none(*pte)) {
> pte_t entry;
> - void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
> + void *p;
> +
> + if (altmap)
> + p = altmap_alloc_block_buf(PAGE_SIZE, altmap);
> + else
> + p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
> if (!p)
> return NULL;
I was wondering if
if (altmap)
p = altmap_alloc_block_buf(PAGE_SIZE, altmap);
if (!p)
p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
if (!p)
return NULL
Would make sense. But I guess this isn't really relevant in practice,
because the altmap is usually sized properly.
In general, LGTM.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-07-06 9:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 2:56 [PATCH V4 0/3] arm64: Enable vmemmap mapping from device memory Anshuman Khandual
2020-07-06 2:56 ` [PATCH V4 1/3] mm/sparsemem: Enable vmem_altmap support in vmemmap_populate_basepages() Anshuman Khandual
2020-07-06 9:03 ` David Hildenbrand [this message]
2020-07-07 3:50 ` Anshuman Khandual
2020-07-07 7:26 ` David Hildenbrand
2020-07-06 2:56 ` [PATCH V4 2/3] mm/sparsemem: Enable vmem_altmap support in vmemmap_alloc_block_buf() Anshuman Khandual
2020-07-08 13:25 ` Catalin Marinas
2020-07-06 2:56 ` [PATCH V4 3/3] arm64/mm: Enable vmem_altmap support for vmemmap mappings Anshuman Khandual
2020-07-09 3:30 ` [PATCH V4 0/3] arm64: Enable vmemmap mapping from device memory Anshuman Khandual
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=eeeb44f9-bc0a-2c3d-8e8f-7e3d9e066c7e@redhat.com \
--to=david@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=catalin.marinas@arm.com \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=fenghua.yu@intel.com \
--cc=justin.he@arm.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-riscv@lists.infradead.org \
--cc=luto@kernel.org \
--cc=mark.rutland@arm.com \
--cc=mhocko@suse.com \
--cc=mingo@redhat.com \
--cc=palmer@dabbelt.com \
--cc=pasha.tatashin@soleen.com \
--cc=paul.walmsley@sifive.com \
--cc=peterz@infradead.org \
--cc=rppt@linux.ibm.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=will@kernel.org \
--cc=willy@infradead.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).