From: Michal Hocko <mhocko@kernel.org>
To: Huaisheng Ye <yehs1@lenovo.com>
Cc: linux-kernel@vger.kernel.org, hehy1@lenovo.com,
penguin-kernel@I-love.SAKURA.ne.jp, chengnt@lenovo.com,
linux-nvdimm@lists.01.org, pasha.tatashin@oracle.com,
willy@infradead.org, alexander.levin@verizon.com,
linux-mm@kvack.org, hannes@cmpxchg.org,
akpm@linux-foundation.org, colyli@suse.de,
mgorman@techsingularity.net, vbabka@suse.cz
Subject: Re: [RFC PATCH v1 0/6] use mm to manage NVDIMM (pmem) zone
Date: Thu, 10 May 2018 10:41:19 +0200 [thread overview]
Message-ID: <20180510084119.GJ32366@dhcp22.suse.cz> (raw)
In-Reply-To: <20180510075759.GF32366@dhcp22.suse.cz>
I have only now noticed that you have posted this few days ago
http://lkml.kernel.org/r/1525704627-30114-1-git-send-email-yehs1@lenovo.com
There were some good questions asked there and I have many that are
common yet they are not covered in the cover letter. Please _always_
make sure to answer review comments before reposting. Otherwise some
important parts gets lost on the way.
On Thu 10-05-18 09:57:59, Michal Hocko wrote:
> On Tue 08-05-18 10:30:22, Huaisheng Ye wrote:
> > Traditionally, NVDIMMs are treated by mm(memory management) subsystem as
> > DEVICE zone, which is a virtual zone and both its start and end of pfn
> > are equal to 0, mm wouldn’t manage NVDIMM directly as DRAM, kernel uses
> > corresponding drivers, which locate at \drivers\nvdimm\ and
> > \drivers\acpi\nfit and fs, to realize NVDIMM memory alloc and free with
> > memory hot plug implementation.
> >
> > With current kernel, many mm’s classical features like the buddy
> > system, swap mechanism and page cache couldn’t be supported to NVDIMM.
> > What we are doing is to expand kernel mm’s capacity to make it to handle
> > NVDIMM like DRAM. Furthermore we make mm could treat DRAM and NVDIMM
> > separately, that means mm can only put the critical pages to NVDIMM
> > zone, here we created a new zone type as NVM zone.
>
> How do you define critical pages? Who is allowed to allocate from them?
> You do not seem to add _any_ user of GFP_NVM.
>
> > That is to say for
> > traditional(or normal) pages which would be stored at DRAM scope like
> > Normal, DMA32 and DMA zones. But for the critical pages, which we hope
> > them could be recovered from power fail or system crash, we make them
> > to be persistent by storing them to NVM zone.
>
> This brings more questions than it answers. First of all is this going
> to be any guarantee? Let's say I want GFP_NVM, can I get memory from
> other zones? In other words is such a request allowed to fallback to
> succeed? Are we allowed to reclaim memory from the new zone? What should
> happen on the OOM? How is the user expected to restore the previous
> content after reboot/crash?
>
> I am sorry if these questions are answered in the respective patches but
> it would be great to have this in the cover letter to have a good
> overview of the whole design. From my quick glance over patches my
> previous concerns about an additional zone still hold, though.
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
next prev parent reply other threads:[~2018-05-10 8:41 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-08 2:30 [RFC PATCH v1 0/6] use mm to manage NVDIMM (pmem) zone Huaisheng Ye
[not found] ` <1525746628-114136-2-git-send-email-yehs1@lenovo.com>
2018-05-08 2:30 ` [External] [RFC PATCH v1 1/6] mm/memblock: Expand definition of flags to support NVDIMM Huaisheng HS1 Ye
2018-05-08 2:30 ` [RFC PATCH v1 4/6] arch/x86/kernel: mark NVDIMM regions from e820_table Huaisheng Ye
[not found] ` <1525746628-114136-3-git-send-email-yehs1@lenovo.com>
2018-05-08 2:32 ` [External] [RFC PATCH v1 2/6] mm/page_alloc.c: get pfn range with flags of memblock Huaisheng HS1 Ye
[not found] ` <1525746628-114136-4-git-send-email-yehs1@lenovo.com>
2018-05-08 2:33 ` [External] [RFC PATCH v1 3/6] mm, zone_type: create ZONE_NVM and fill into GFP_ZONE_TABLE Huaisheng HS1 Ye
2018-05-08 4:43 ` Randy Dunlap
2018-05-09 4:22 ` Huaisheng HS1 Ye
2018-05-09 11:47 ` Michal Hocko
2018-05-09 14:04 ` Huaisheng HS1 Ye
2018-05-09 20:56 ` Michal Hocko
2018-05-10 3:53 ` Huaisheng HS1 Ye
[not found] ` <1525746628-114136-6-git-send-email-yehs1@lenovo.com>
2018-05-08 2:34 ` [External] [RFC PATCH v1 5/6] mm: get zone spanned pages separately for DRAM and NVDIMM Huaisheng HS1 Ye
[not found] ` <1525746628-114136-7-git-send-email-yehs1@lenovo.com>
2018-05-08 2:35 ` [External] [RFC PATCH v1 6/6] arch/x86/mm: create page table mapping for DRAM and NVDIMM both Huaisheng HS1 Ye
2018-05-10 7:57 ` [RFC PATCH v1 0/6] use mm to manage NVDIMM (pmem) zone Michal Hocko
2018-05-10 8:41 ` Michal Hocko [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-05-08 2:00 Huaisheng Ye
[not found] <1525704627-30114-1-git-send-email-yehs1@lenovo.com>
2018-05-07 18:46 ` Matthew Wilcox
2018-05-07 18:57 ` Dan Williams
2018-05-07 19:08 ` Jeff Moyer
2018-05-07 19:17 ` Dan Williams
2018-05-07 19:28 ` Jeff Moyer
2018-05-07 19:29 ` Dan Williams
2018-05-07 19:18 ` Matthew Wilcox
2018-05-07 19:30 ` Dan Williams
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=20180510084119.GJ32366@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=alexander.levin@verizon.com \
--cc=chengnt@lenovo.com \
--cc=colyli@suse.de \
--cc=hannes@cmpxchg.org \
--cc=hehy1@lenovo.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nvdimm@lists.01.org \
--cc=mgorman@techsingularity.net \
--cc=pasha.tatashin@oracle.com \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
--cc=yehs1@lenovo.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 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).