From: Dan Williams <firstname.lastname@example.org> To: Gerald Schaefer <email@example.com> Cc: "Christoph Hellwig" <firstname.lastname@example.org>, "Jan Kara" <email@example.com>, linux-nvdimm <firstname.lastname@example.org>, "Martin Schwidefsky" <email@example.com>, "Heiko Carstens" <firstname.lastname@example.org>, "Michal Hocko" <email@example.com>, "kbuild test robot" <firstname.lastname@example.org>, "Thomas Meyer" <email@example.com>, "Dave Jiang" <firstname.lastname@example.org>, "Jérôme Glisse" <email@example.com>, linux-fsdevel <firstname.lastname@example.org>, "Linux MM" <email@example.com> Subject: Re: [PATCH v10] mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS Date: Fri, 1 Jun 2018 17:03:55 -0700 [thread overview] Message-ID: <CAPcyv4is_iW6UjVrb4ZKJh=EuGjnCxm=O49kNAtOF5nrQG4+Ag@mail.gmail.com> (raw) In-Reply-To: <20180601170100.0a8e5567@thinkpad> On Fri, Jun 1, 2018 at 8:01 AM, Gerald Schaefer <firstname.lastname@example.org> wrote: > On Tue, 29 May 2018 13:26:33 -0700 > Dan Williams <email@example.com> wrote: > >> On Wed, May 23, 2018 at 11:50 AM, Gerald Schaefer >> <firstname.lastname@example.org> wrote: >> > On Tue, 22 May 2018 08:28:06 +0200 >> > Christoph Hellwig <email@example.com> wrote: >> > >> >> On Mon, May 21, 2018 at 11:04:10AM +0200, Jan Kara wrote: >> >> > We definitely do have customers using "execute in place" on s390x from >> >> > dcssblk. I've got about two bug reports for it when customers were updating >> >> > from old kernels using original XIP to kernels using DAX. So we need to >> >> > keep that working. >> >> >> >> That is all good an fine, but I think time has come where s390 needs >> >> to migrate to provide the pmem API so that we can get rid of these >> >> special cases. Especially given that the old XIP/legacy DAX has all >> >> kinds of known bugs at this point in time. >> > >> > I haven't yet looked at this patch series, but I can feel that this >> > FS_DAX_LIMITED workaround is beginning to cause some headaches, apart >> > from being quite ugly of course. >> > >> > Just to make sure I still understand the basic problem, which I thought >> > was missing struct pages for the dcssblk memory, what exactly do you >> > mean with "provide the pmem API", is there more to do? >> >> No, just 'struct page' is needed. >> >> What used to be the pmem API is now pushed down into to dax_operations >> provided by the device driver. dcssblk is free to just redirect to the >> generic implementations for copy_from_iter() and copy_to_iter(), and >> be done. I.e. we've removed the "pmem API" requirement. >> >> > I do have a prototype patch lying around that adds struct pages, but >> > didn't yet have time to fully test/complete it. Of course we initially >> > introduced XIP as a mechanism to reduce memory consumption, and that >> > is probably the use case for the remaining customer(s). Adding struct >> > pages would somehow reduce that benefit, but as long as we can still >> > "execute in place", I guess it will be OK. >> >> The pmem driver has the option to allocate the 'struct page' map out >> of pmem directly. If the overhead of having the map in System RAM is >> too high it could borrow the same approach, but that adds another >> degree of configuration complexity freedom. >> > > Thanks for clarifying, and mentioning the pmem altmap support, that > looks interesting. I also noticed that I probably should enable > CONFIG_ZONE_DEVICE for s390, and use devm_memremap_pages() to get > the struct pages, rather than my homegrown solution so far. This will > take some time however, so I hope you can live with the FS_DAX_LIMITED > a little longer. > Yes, no urgent rush as far as I can see. Thanks Gerald.
prev parent reply other threads:[~2018-06-02 0:03 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-17 20:06 Dan Williams 2018-05-18 9:00 ` Jan Kara 2018-05-18 9:46 ` Christoph Hellwig 2018-05-18 16:00 ` Dan Williams 2018-05-21 9:04 ` Jan Kara 2018-05-22 6:28 ` Christoph Hellwig 2018-05-23 18:50 ` Gerald Schaefer 2018-05-29 20:26 ` Dan Williams 2018-06-01 15:01 ` Gerald Schaefer 2018-06-02 0:03 ` Dan Williams [this message]
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='CAPcyv4is_iW6UjVrb4ZKJh=EuGjnCxm=O49kNAtOF5nrQG4+Ag@mail.gmail.com' \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --subject='Re: [PATCH v10] mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS' \ /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
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).