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Date: Mon, 15 Sep 2014 16:20:01 -0400 From: Milosz Tanski <milosz@...in.com> To: linux-kernel@...r.kernel.org Cc: Christoph Hellwig <hch@...radead.org>, linux-fsdevel@...r.kernel.org, linux-aio@...ck.org, Mel Gorman <mgorman@...e.de>, Volker Lendecke <Volker.Lendecke@...net.de>, Tejun Heo <tj@...nel.org>, Jeff Moyer <jmoyer@...hat.com> Subject: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) 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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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