On Mon, Sep 15, 2014 at 10:36:46PM +0000, Elliott, Robert (Server Storage) wrote: > > > > -----Original Message----- > > From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Andreas Dilger > > Sent: Monday, 15 September, 2014 4:34 PM > > To: Milosz Tanski > > Cc: linux-kernel@xxxxxxxxxxxxxxx; Christoph Hellwig; linux- > > fsdevel@xxxxxxxxxxxxxxx; linux-aio@xxxxxxxxx; Mel Gorman; Volker Lendecke; > > Tejun Heo; Jeff Moyer > > Subject: Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) > > > > On Sep 15, 2014, at 2:20 PM, Milosz Tanski <milosz@xxxxxxxxx> 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 > > That sounds like the proposed WRITE SCATTERED/READ GATHERED > commands for SCSI (where are related to, but not necessarily > tied to, atomic writes). We discussed them a bit at > LSF-MM 2013 - see http://lwn.net/Articles/548116/. It's the old {read,write}x proposals: http://www.mcs.anl.gov/uploads/cels/papers/TM-302-FINAL.pdf - z -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
