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Date: Mon, 15 Sep 2014 22:36:46 +0000 From: "Elliott, Robert (Server Storage)" <Elliott@...com> To: Andreas Dilger <adilger@...ger.ca>, Milosz Tanski <milosz@...in.com> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Christoph Hellwig" <hch@...radead.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-aio@...ck.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: RE: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) > -----Original Message----- > From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel- > owner@...r.kernel.org] On Behalf Of Andreas Dilger > Sent: Monday, 15 September, 2014 4:34 PM > To: Milosz Tanski > Cc: linux-kernel@...r.kernel.org; Christoph Hellwig; linux- > fsdevel@...r.kernel.org; linux-aio@...ck.org; 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@...in.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 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/. --- Rob Elliott HP Server Storage -- 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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