From: Mikulas Patocka <mpatocka@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Ira Weiny <ira.weiny@intel.com>, Jan Kara <jack@suse.cz>,
Eric Sandeen <esandeen@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
"Kani, Toshi" <toshi.kani@hpe.com>,
"Norton, Scott J" <scott.norton@hpe.com>,
"Tadakamadla,
Rajesh (DCIG/CDI/HPS Perf)" <rajesh.tadakamadla@hpe.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache)
Date: Tue, 22 Sep 2020 08:39:11 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.2009220831170.20550@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20200922122819.GD32101@casper.infradead.org>
On Tue, 22 Sep 2020, Matthew Wilcox wrote:
> On Mon, Sep 21, 2020 at 12:20:42PM -0400, Mikulas Patocka wrote:
> > The same for directories - NVFS hashes the file name and uses radix-tree
> > to locate a directory page where the directory entry is located. XFS
> > b+trees would result in much more accesses than the radix-tree.
>
> What? Radix trees behave _horribly_ badly when indexed by a hash.
> If you have a 64-bit hash and use 8 bits per level of the tree, you have
> to traverse 8 pointers to get to your destination. You might as well
> use a linked list!
In NVFS, radix trees are cut off - they have only as much internal levels,
as is needed to disambiguate the directory entries.
Read this document: http://people.redhat.com/~mpatocka/nvfs/INTERNALS
the section "DIRECTORIES".
Perhaps, I should call it differently than "radix-trees", but I don't
really know what is the official name for this data structure.
Mikulas
next prev parent reply other threads:[~2020-09-22 12:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 12:34 [RFC] nvfs: a filesystem for persistent memory Mikulas Patocka
2020-09-15 13:00 ` Matthew Wilcox
2020-09-15 13:24 ` Mikulas Patocka
2020-09-22 10:04 ` Ritesh Harjani
2020-09-15 15:16 ` Dan Williams
2020-09-15 16:58 ` Mikulas Patocka
2020-09-15 17:38 ` Mikulas Patocka
2020-09-16 10:57 ` [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache Mikulas Patocka
2020-09-16 16:21 ` Dan Williams
2020-09-16 17:24 ` Mikulas Patocka
2020-09-16 17:40 ` Dan Williams
2020-09-16 18:06 ` Mikulas Patocka
2020-09-21 16:20 ` NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache) Mikulas Patocka
2020-09-22 5:03 ` Dave Chinner
2020-09-22 16:46 ` Mikulas Patocka
2020-09-22 17:25 ` Matthew Wilcox
2020-09-24 15:00 ` Mikulas Patocka
2020-09-28 15:22 ` Mikulas Patocka
2020-09-23 2:45 ` Dave Chinner
2020-09-23 9:20 ` A bug in ext4 with big directories (was: NVFS XFS metadata) Mikulas Patocka
2020-09-23 9:44 ` Jan Kara
2020-09-23 12:46 ` Mikulas Patocka
2020-09-23 17:19 ` NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache) Mikulas Patocka
2020-09-23 9:57 ` Jan Kara
2020-09-23 13:11 ` Mikulas Patocka
2020-09-23 15:04 ` Matthew Wilcox
2020-09-22 12:28 ` Matthew Wilcox
2020-09-22 12:39 ` Mikulas Patocka [this message]
2020-09-16 18:56 ` [PATCH] pmem: fix __copy_user_flushcache Mikulas Patocka
2020-09-18 1:53 ` Dan Williams
2020-09-18 12:25 ` the "read" syscall sees partial effects of the "write" syscall Mikulas Patocka
2020-09-18 13:13 ` Jan Kara
2020-09-18 18:02 ` Linus Torvalds
2020-09-20 23:41 ` Dave Chinner
2020-09-17 6:50 ` [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache Christoph Hellwig
2020-09-21 16:19 ` [RFC] nvfs: a filesystem for persistent memory Mikulas Patocka
2020-09-21 16:29 ` Dan Williams
2020-09-22 15:43 ` Ira Weiny
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