Linux-NVDIMM Archive on lore.kernel.org
 help / color / Atom feed
From: Won-Kyo Choe <wkyo.choe@gmail.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org
Subject: Re: [QUESTION] Error on initializing dax by using different struct page size
Date: Fri, 8 Nov 2019 04:00:18 +0900
Message-ID: <20191107190018.GB1912@swarm07> (raw)
In-Reply-To: <CAPcyv4j-rSy-T5Qv6GbcDcmUerhQQYsMKbUY7EaGHz-GecKDtQ@mail.gmail.com>

On Thu, Nov 07, 2019 at 07:54:21AM -0800, Dan Williams wrote:
> On Thu, Nov 7, 2019 at 7:30 AM Won-Kyo Choe <wkyo.choe@gmail.com> wrote:
> >
> > Hi, there. I'm using Opatne DC memory to use it a volatile memory. Recently,
> > I found that if sizeof(struct page) is above 64 bytes (e.g. 128 byes),
> > `device_dax` cannot be initialized when system boots. I am aware that
> > for some reason there is a function, `__mm_zero_struct_page`, which limits
> > the size of struct page when it exceeds 80 bytes. However, due to the
> > research purpose, I do not use that constraint and I'm quite certain
> > that using different page size is usable in main memory. So, I'm
> > wondering why this is not possible in persistent memory and which
> > patches are related to this problem.
> >
> > I will attach the system log for clarification. The test is run in
> > linux-5.3.9 and linuxt-5.3-rc5
> 
> How did you manage to build the kernel with a 128byte struct page
> size? This build assert in drivers/nvdimm/pfn_devs.c
> 
>                 BUILD_BUG_ON(sizeof(struct page) > MAX_STRUCT_PAGE_SIZE);
> 
> ...will start to trigger in v5.4 to explicitly prevent this going
> forward. See commit e96f0bf2ec92 "libnvdimm/pfn_dev: Add a build check
> to make sure we notice when struct page size change" for more details.
> 
Thanks for the related commit. The kernel that I am using (5.3.9 / 5.3-rc5) does
not have the assert so that I was able to build it by little bit modifying lines
in include/linux/mm.h

        BUILD_BUG_ON(sizeof(struct page) > 80);
        ...

, which is quite similar with the assert you referred.

> In general 64-bytes per page is already expensive 128 bytes is a
> gigantic struct page.
Yes. I am aware that issue. I just wanted to add hot-page tracking
feature by inserting some data structure collecting it inside struct page
but the size is matter. I should find another way to get that stat :)

(Sorry, I should've put cc on this mail)

Thanks,

Won-Kyo
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 15:29 Won-Kyo Choe
2019-11-07 15:54 ` Dan Williams
2019-11-07 19:00   ` Won-Kyo Choe [this message]
2019-11-07 19:24     ` Dan Williams
2019-11-08  4:26       ` Won-Kyo Choe

Reply instructions:

You may reply publically 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=20191107190018.GB1912@swarm07 \
    --to=wkyo.choe@gmail.com \
    --cc=dan.j.williams@intel.com \
    --cc=linux-nvdimm@lists.01.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

Linux-NVDIMM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvdimm/0 linux-nvdimm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nvdimm linux-nvdimm/ https://lore.kernel.org/linux-nvdimm \
		linux-nvdimm@lists.01.org
	public-inbox-index linux-nvdimm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.01.lists.linux-nvdimm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git