From: Andreas Dilger <adilger@dilger.ca>
To: Milosz Tanski <milosz@adfin.com>
Cc: linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
Mel Gorman <mgorman@suse.de>,
Volker Lendecke <Volker.Lendecke@sernet.de>,
Tejun Heo <tj@kernel.org>, Jeff Moyer <jmoyer@redhat.com>
Subject: Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only)
Date: Mon, 15 Sep 2014 15:33:47 -0600 [thread overview]
Message-ID: <8EC2A7F3-0E25-4054-9863-4488B8ED5C8D@dilger.ca> (raw)
In-Reply-To: <cover.1410810247.git.milosz@adfin.com>
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On Sep 15, 2014, at 2:20 PM, Milosz Tanski <milosz@adfin.com> wrote:
> This patcheset introduces an ability to perform a non-blocking read
> from regular files in buffered IO mode. This works by only for those
> filesystems that have data in the page cache.
>
> It does this by introducing new syscalls new syscalls readv2/writev2
> and preadv2/pwritev2. These new syscalls behave like the network sendmsg,
> recvmsg syscalls that accept an extra flag argument (O_NONBLOCK).
It's too bad that we are introducing yet another new read/write
syscall pair that only allow IO into discontiguous memory regions,
but do not allow a single call to access discontiguous file regions
(i.e. specify a separate file offset for each iov).
Adding syscalls similar to preadv/pwritev() that could take a iovec
that specified the file offset+length in addition to the memory address
would allow efficient scatter-gather IO in a single syscall. While
that is less critical for local filesystems with small syscall latency,
it is more important for network filesystems, or in the case of
NVRAM-backed filesystems.
Cheers, Andreas
> It's a very common patern today (samba, libuv, etc..) use a large
> threadpool to perform buffered IO operations. They submit the work
> form another thread that performs network IO and epoll or other threads
> that perform CPU work. This leads to increased latency for processing,
> esp. in the case of data that's already cached in the page cache.
>
> With the new interface the applications will now be able to fetch the
> data in their network / cpu bound thread(s) and only defer to a
> threadpool if it's not there. In our own application (VLDB) we've
> observed a decrease in latency for "fast" request by avoiding unnecessary
> queuing and having to swap out current tasks in IO bound work threads.
>
> I have co-developed these changes with Christoph Hellwig, a whole lot
> of his fixes went into the first patch in the series (were squashed
> with his approval).
>
> I am going to post the perf report in a reply-to to this RFC.
>
> Christoph Hellwig (3):
> documentation updates
> move flags enforcement to vfs_preadv/vfs_pwritev
> check for O_NONBLOCK in all read_iter instances
>
> Milosz Tanski (4):
> Prepare for adding a new readv/writev with user flags.
> Define new syscalls readv2,preadv2,writev2,pwritev2
> Export new vector IO (with flags) to userland
> O_NONBLOCK flag for readv2/preadv2
>
> Documentation/filesystems/Locking | 4 +-
> Documentation/filesystems/vfs.txt | 4 +-
> arch/x86/syscalls/syscall_32.tbl | 4 +
> arch/x86/syscalls/syscall_64.tbl | 4 +
> drivers/target/target_core_file.c | 6 +-
> fs/afs/internal.h | 2 +-
> fs/afs/write.c | 4 +-
> fs/aio.c | 4 +-
> fs/block_dev.c | 9 ++-
> fs/btrfs/file.c | 2 +-
> fs/ceph/file.c | 10 ++-
> fs/cifs/cifsfs.c | 9 ++-
> fs/cifs/cifsfs.h | 12 ++-
> fs/cifs/file.c | 30 +++++---
> fs/ecryptfs/file.c | 4 +-
> fs/ext4/file.c | 4 +-
> fs/fuse/file.c | 10 ++-
> fs/gfs2/file.c | 5 +-
> fs/nfs/file.c | 13 ++--
> fs/nfs/internal.h | 4 +-
> fs/nfsd/vfs.c | 4 +-
> fs/ocfs2/file.c | 13 +++-
> fs/pipe.c | 7 +-
> fs/read_write.c | 146 +++++++++++++++++++++++++++++++------
> fs/splice.c | 4 +-
> fs/ubifs/file.c | 5 +-
> fs/udf/file.c | 5 +-
> fs/xfs/xfs_file.c | 12 ++-
> include/linux/fs.h | 16 ++--
> include/linux/syscalls.h | 12 +++
> include/uapi/asm-generic/unistd.h | 10 ++-
> mm/filemap.c | 34 +++++++--
> mm/shmem.c | 6 +-
> 33 files changed, 306 insertions(+), 112 deletions(-)
>
> --
> 1.7.9.5
>
> --
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
Cheers, Andreas
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next prev parent reply other threads:[~2014-09-15 21:33 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-15 20:20 [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-15 20:20 ` [PATCH 1/7] Prepare for adding a new readv/writev with user flags Milosz Tanski
2014-09-15 20:28 ` Al Viro
2014-09-15 21:15 ` Christoph Hellwig
2014-09-15 21:44 ` Milosz Tanski
2014-09-15 20:20 ` [PATCH 2/7] Define new syscalls readv2,preadv2,writev2,pwritev2 Milosz Tanski
2014-09-16 19:20 ` Jeff Moyer
2014-09-16 19:54 ` Milosz Tanski
2014-09-16 21:03 ` Christoph Hellwig
2014-09-17 15:43 ` Theodore Ts'o
2014-09-17 16:05 ` Milosz Tanski
2014-09-17 16:59 ` Theodore Ts'o
2014-09-17 17:24 ` Zach Brown
2014-09-15 20:20 ` [PATCH 3/7] Export new vector IO (with flags) to userland Milosz Tanski
2014-09-15 20:21 ` [PATCH 4/7] O_NONBLOCK flag for readv2/preadv2 Milosz Tanski
2014-09-16 19:19 ` Jeff Moyer
2014-09-16 19:44 ` Milosz Tanski
2014-09-16 19:53 ` Jeff Moyer
2014-09-15 20:21 ` [PATCH 5/7] documentation updates Christoph Hellwig
2014-09-15 20:21 ` [PATCH 6/7] move flags enforcement to vfs_preadv/vfs_pwritev Christoph Hellwig
2014-09-15 21:15 ` Christoph Hellwig
2014-09-15 21:45 ` Milosz Tanski
2014-09-15 20:22 ` [PATCH 7/7] check for O_NONBLOCK in all read_iter instances Christoph Hellwig
2014-09-16 19:27 ` Jeff Moyer
2014-09-16 19:45 ` Milosz Tanski
2014-09-16 21:42 ` Dave Chinner
2014-09-17 12:24 ` Benjamin LaHaise
2014-09-17 13:47 ` Theodore Ts'o
2014-09-17 13:56 ` Benjamin LaHaise
2014-09-17 15:33 ` Milosz Tanski
2014-09-17 15:49 ` Theodore Ts'o
2014-09-17 15:52 ` Zach Brown
2014-09-16 21:04 ` Christoph Hellwig
2014-09-16 21:24 ` Jeff Moyer
2014-09-15 20:27 ` [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-15 21:33 ` Andreas Dilger [this message]
2014-09-15 22:13 ` Milosz Tanski
2014-09-15 22:36 ` Elliott, Robert (Server Storage)
2014-09-16 18:24 ` Zach Brown
2014-09-19 11:21 ` Christoph Hellwig
2014-09-22 15:48 ` Jeff Moyer
2014-09-22 16:32 ` Milosz Tanski
2014-09-22 16:42 ` Christoph Hellwig
2014-09-22 17:02 ` Milosz Tanski
2014-09-22 16:25 ` Elliott, Robert (Server Storage)
2014-09-15 21:58 ` Jeff Moyer
2014-09-15 22:27 ` Milosz Tanski
2014-09-16 13:44 ` Jeff Moyer
2014-09-19 11:23 ` Christoph Hellwig
2014-09-16 19:30 ` Jeff Moyer
2014-09-16 20:34 ` Milosz Tanski
2014-09-16 20:49 ` Jeff Moyer
2014-09-17 14:49 ` [RFC 1/2] aio: async readahead Benjamin LaHaise
2014-09-17 15:26 ` [RFC 2/2] ext4: async readpage for indirect style inodes Benjamin LaHaise
2014-09-19 11:26 ` [RFC 1/2] aio: async readahead Christoph Hellwig
2014-09-19 16:01 ` Benjamin LaHaise
2014-09-17 22:20 ` [RFC v2 0/5] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-17 22:20 ` [RFC v2 1/5] Prepare for adding a new readv/writev with user flags Milosz Tanski
2014-09-17 22:20 ` [RFC v2 2/5] Define new syscalls readv2,preadv2,writev2,pwritev2 Milosz Tanski
2014-09-18 18:48 ` Darrick J. Wong
2014-09-19 10:52 ` Christoph Hellwig
2014-09-20 0:19 ` Darrick J. Wong
2014-09-17 22:20 ` [RFC v2 3/5] Export new vector IO (with flags) to userland Milosz Tanski
2014-09-17 22:20 ` [RFC v2 4/5] O_NONBLOCK flag for readv2/preadv2 Milosz Tanski
2014-09-19 11:27 ` Christoph Hellwig
2014-09-19 11:59 ` Milosz Tanski
2014-09-22 17:12 ` Jeff Moyer
2014-09-17 22:20 ` [RFC v2 5/5] Check for O_NONBLOCK in all read_iter instances Milosz Tanski
2014-09-19 11:26 ` Christoph Hellwig
2014-09-19 14:42 ` [RFC v2 0/5] Non-blockling buffered fs read (page cache only) Jonathan Corbet
2014-09-19 16:13 ` Volker Lendecke
2014-09-19 17:19 ` Milosz Tanski
2014-09-19 17:33 ` Milosz Tanski
2014-09-22 14:12 ` Jonathan Corbet
2014-09-22 14:24 ` Jeff Moyer
2014-09-22 14:25 ` Christoph Hellwig
2014-09-22 14:30 ` Milosz Tanski
2014-09-24 21:46 ` [RFC v3 0/4] vfs: " Milosz Tanski
2014-09-24 21:46 ` [RFC v3 1/4] vfs: Prepare for adding a new preadv/pwritev with user flags Milosz Tanski
2014-09-24 21:46 ` [RFC v3 2/4] vfs: Define new syscalls preadv2,pwritev2 Milosz Tanski
2014-09-24 21:46 ` [RFC v3 3/4] vfs: Export new vector IO syscalls (with flags) to userland Milosz Tanski
2014-09-24 21:46 ` [RFC v3 4/4] vfs: RWF_NONBLOCK flag for preadv2 Milosz Tanski
2014-09-25 4:06 ` [RFC v3 0/4] vfs: Non-blockling buffered fs read (page cache only) Michael Kerrisk
2014-09-25 11:16 ` Jan Kara
2014-09-25 15:48 ` Milosz Tanski
2014-10-08 2:53 ` Milosz Tanski
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