From: Matthew Wilcox <willy@infradead.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: Baoquan He <bhe@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
mhocko@suse.com, akpm@linux-foundation.org, david@redhat.com
Subject: Re: [PATCH v2] mm/sparse.c: Use kvmalloc_node/kvfree to alloc/free memmap for the classic sparse
Date: Thu, 12 Mar 2020 17:00:41 -0700 [thread overview]
Message-ID: <20200313000041.GM22433@bombadil.infradead.org> (raw)
In-Reply-To: <20200312225055.ksn4ujtkpjgkqiaf@master>
On Thu, Mar 12, 2020 at 10:50:55PM +0000, Wei Yang wrote:
> On Thu, Mar 12, 2020 at 07:25:35AM -0700, Matthew Wilcox wrote:
> >Yes, I thought about that. I decided it wasn't a problem, as long as
> >the struct page remains aligned, and we now have a guarantee that allocations
> >above 512 bytes in size are aligned. With a 64 byte struct page, as long
>
> Where is this 512 bytes condition comes from?
Filesystems need to do I/Os from kmalloc addresses and those I/Os need to
be 512 byte aligned.
> >as we're allocating at least 8 pages, we know it'll be naturally aligned.
> >
> >Your calculation doesn't take into account the size of struct page.
> >128M / 64k is indeed 2k, but you forgot to multiply by 64, which takes
> >us to 128kB.
>
> You are right. While would there be other combination? Or in the future?
>
> For example, there are definitions of
>
> #define SECTION_SIZE_BITS 26
> #define SECTION_SIZE_BITS 24
>
> Are we sure it won't break some thing?
As I said, once it's at least 512 bytes, it'll be 512 byte aligned. And I
can't see us having sections smaller than 8 pages, can you?
next prev parent reply other threads:[~2020-03-13 0:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 13:08 [PATCH v2] mm/sparse.c: Use kvmalloc_node/kvfree to alloc/free memmap for the classic sparse Baoquan He
2020-03-12 13:34 ` Matthew Wilcox
2020-03-12 13:54 ` Baoquan He
2020-03-12 14:18 ` Wei Yang
2020-03-12 14:25 ` Matthew Wilcox
2020-03-12 22:50 ` Wei Yang
2020-03-13 0:00 ` Matthew Wilcox [this message]
2020-03-13 14:35 ` David Hildenbrand
2020-03-13 14:46 ` Vlastimil Babka
2020-03-13 14:57 ` Michal Hocko
2020-03-13 21:54 ` Wei Yang
2020-03-12 14:17 ` [PATCH v3] " Baoquan He
2020-03-13 14:56 ` Michal Hocko
2020-03-14 0:53 ` Baoquan He
2020-03-14 12:56 ` Michal Hocko
2020-03-15 13:01 ` Baoquan He
2020-03-14 1:12 ` Baoquan He
2020-03-13 15:04 ` David Hildenbrand
2020-03-16 7:14 ` Baoquan He
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=20200313000041.GM22433@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=bhe@redhat.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=richard.weiyang@gmail.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.