From: Rik van Riel <riel@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: John Stoffel <john@stoffel.org>, Ingo Molnar <mingo@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Boaz Harrosh <boaz@plexistor.com>, Jan Kara <jack@suse.cz>,
Mike Snitzer <snitzer@redhat.com>, Neil Brown <neilb@suse.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Chris Mason <clm@fb.com>, Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>, Christoph Hellwig <hch@lst.de>,
Alasdair Kergon <agk@redhat.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
Mel Gorman <mgorman@suse.de>,
Matthew Wilcox <willy@linux.intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Jens Axboe <axboe@kernel.dk>, Theodore Ts'o <tytso@mit.edu>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Julia Lawall <Julia.Lawall@lip6.fr>, Tejun Heo <tj@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 00/10] evacuate struct page from the block layer, introduce __pfn_t
Date: Fri, 08 May 2015 23:02:28 -0400 [thread overview]
Message-ID: <554D78C4.30607@redhat.com> (raw)
In-Reply-To: <CA+55aFzeCiRSbzsX_NfScqF_-1JiVWj62Qo00pRttZp_s3hCVw@mail.gmail.com>
On 05/08/2015 09:14 PM, Linus Torvalds wrote:
> On Fri, May 8, 2015 at 9:59 AM, Rik van Riel <riel@redhat.com> wrote:
>>
>> However, for persistent memory, all of the files will be "in memory".
>
> Yes. However, I doubt you will find a very sane rw filesystem that
> then also makes them contiguous and aligns them at 2MB boundaries.
>
> Anything is possible, I guess, but things like that are *hard*. The
> fragmentation issues etc cause it to a really challenging thing.
The TLB performance bonus of accessing the large files with
large pages may make it worthwhile to solve that hard problem.
> And if they aren't aligned big contiguous allocations, then they
> aren't relevant from any largepage cases. You'll still have to map
> them 4k at a time etc.
Absolutely, but we only need the 4k struct pages when the
files are mapped. I suspect a lot of the files will just
sit around idle, without being used.
I am not convinced that the idea I wrote down earlier in
this thread is worthwhile now, but it may turn out to be
at some point in the future. It all depends on how much
data people store on DAX filesystems, and how many files
they have open at once.
--
All rights reversed
next prev parent reply other threads:[~2015-05-09 3:02 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-06 20:04 [PATCH v2 00/10] evacuate struct page from the block layer, introduce __pfn_t Dan Williams
2015-05-06 20:04 ` [PATCH v2 01/10] arch: introduce __pfn_t for persistent memory i/o Dan Williams
2015-05-07 14:55 ` Stephen Rothwell
2015-05-08 0:21 ` Dan Williams
2015-05-06 20:05 ` [PATCH v2 02/10] block: add helpers for accessing a bio_vec page Dan Williams
2015-05-08 15:59 ` Dan Williams
2015-05-06 20:05 ` [PATCH v2 03/10] block: convert .bv_page to .bv_pfn bio_vec Dan Williams
2015-05-06 20:05 ` [PATCH v2 04/10] dma-mapping: allow archs to optionally specify a ->map_pfn() operation Dan Williams
2015-05-06 20:05 ` [PATCH v2 05/10] scatterlist: use sg_phys() Dan Williams
2015-05-06 20:05 ` [PATCH v2 06/10] scatterlist: support "page-less" (__pfn_t only) entries Dan Williams
2015-05-06 20:05 ` [PATCH v2 07/10] x86: support dma_map_pfn() Dan Williams
2015-05-06 20:05 ` [PATCH v2 08/10] x86: support kmap_atomic_pfn_t() for persistent memory Dan Williams
2015-05-06 20:20 ` [Linux-nvdimm] " Dan Williams
2015-05-06 20:05 ` [PATCH v2 09/10] dax: convert to __pfn_t Dan Williams
2015-05-06 20:05 ` [PATCH v2 10/10] block: base support for pfn i/o Dan Williams
2015-05-06 22:10 ` [PATCH v2 00/10] evacuate struct page from the block layer, introduce __pfn_t Linus Torvalds
2015-05-06 23:47 ` Dan Williams
2015-05-07 0:19 ` Linus Torvalds
2015-05-07 2:36 ` Dan Williams
2015-05-07 9:02 ` Ingo Molnar
2015-05-07 14:42 ` Ingo Molnar
2015-05-07 15:52 ` Dan Williams
2015-05-07 17:52 ` Ingo Molnar
2015-05-07 15:00 ` Linus Torvalds
2015-05-07 15:40 ` Dan Williams
2015-05-07 15:58 ` Linus Torvalds
2015-05-07 16:03 ` Dan Williams
2015-05-07 17:36 ` Ingo Molnar
2015-05-07 17:42 ` Dan Williams
2015-05-07 17:56 ` Dave Hansen
2015-05-07 19:11 ` Ingo Molnar
2015-05-07 19:36 ` Jerome Glisse
2015-05-07 19:48 ` Ingo Molnar
2015-05-07 19:53 ` Ingo Molnar
2015-05-07 20:18 ` Jerome Glisse
2015-05-08 5:37 ` Ingo Molnar
2015-05-08 9:20 ` Al Viro
2015-05-08 9:26 ` Ingo Molnar
2015-05-08 10:00 ` Al Viro
2015-05-08 13:45 ` Rik van Riel
2015-05-08 14:05 ` Ingo Molnar
2015-05-08 14:54 ` Rik van Riel
[not found] ` <21836.51957.715473.780762@quad.stoffel.home>
2015-05-08 15:54 ` Linus Torvalds
2015-05-08 16:28 ` Al Viro
2015-05-08 16:59 ` Rik van Riel
2015-05-09 1:14 ` Linus Torvalds
2015-05-09 3:02 ` Rik van Riel [this message]
2015-05-09 3:52 ` Linus Torvalds
2015-05-09 21:56 ` Dave Chinner
2015-05-09 8:45 ` "Directly mapped persistent memory page cache" Ingo Molnar
2015-05-09 18:24 ` Dan Williams
2015-05-10 9:46 ` Ingo Molnar
2015-05-10 17:29 ` Dan Williams
[not found] ` <87r3qpyciy.fsf@x220.int.ebiederm.org>
2015-05-10 10:07 ` Ingo Molnar
2015-05-11 8:25 ` Dave Chinner
2015-05-11 9:18 ` Ingo Molnar
2015-05-11 10:12 ` Zuckerman, Boris
2015-05-11 10:38 ` Ingo Molnar
2015-05-12 0:53 ` Dave Chinner
2015-05-12 14:47 ` Jerome Glisse
2015-06-05 5:43 ` Dan Williams
2015-05-11 14:31 ` Matthew Wilcox
2015-05-11 20:01 ` Jerome Glisse
2015-05-07 17:43 ` [PATCH v2 00/10] evacuate struct page from the block layer, introduce __pfn_t Linus Torvalds
2015-05-07 20:06 ` Dan Williams
2015-05-07 16:18 ` Christoph Hellwig
2015-05-07 16:41 ` Dan Williams
2015-05-07 18:40 ` Ingo Molnar
2015-05-07 19:44 ` Dan Williams
2015-05-07 17:30 ` Jerome Glisse
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