Date: Wed, 11 Jan 2012 10:56:37 -0800 From: mdf@FreeBSD.org To: Rick Macklem <rmacklem@uoguelph.ca> Cc: "Mikhail T." <mi+thun@aldan.algebra.com>, fs@freebsd.org Subject: Re: How to best send files over network? Message-ID: <CAMBSHm_eyksPRui2AWSbOBsU6==nSB5MHo6bvPPuOE1LPmvp8g@mail.gmail.com> In-Reply-To: <1235110182.47136.1326298038118.JavaMail.root@erie.cs.uoguelph.ca> References: <4F0D268B.9060908@aldan.algebra.com> <1235110182.47136.1326298038118.JavaMail.root@erie.cs.uoguelph.ca>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Jan 11, 2012 at 8:07 AM, Rick Macklem <rmacklem@uoguelph.ca> wrote: > Mikhail T. wrote: >> On 10.01.2012 18:49, Bob Friesenhahn wrote: >> > Don't use mmap on zfs since doing so wastes memory (zfs ARC is not >> > coherent with mmap page cache). Instead do normal file I/O (e.g. >> > write, fwrite) using the filesystem blocksize (e.g. 128K) or a small >> > multiple thereof. >> Well, that was the reason cited for not using sendfile over ZFS. But >> mmap/write, it was claimed, was efficient. >> >> What's the general opinion of using mmap/write, when the file is on >> UFS? >> Is it just as good as sendfile, or can sendfile be better under some >> circumstances? >> >> > It is useful to cache several blocks on the receiving end and use a >> > thread to receive data from the network in case zfs temporarily >> > stalls >> > during write (which it periodically does). >> No, thanks. I'm certainly not doing a read/write loop -- that's just >> too >> disgusting in the age of better interfaces (even if those aren't well >> implemented yet) :-) > > I think Bob was referring to the receive end and not the send end, which > might be why the answer didn't make sense to you? (For the receive end, > it sounds like a good suggestion to me.) Some day, when there's time, I'd like to roll up Isilon's recvfile(2) into a proper patch. It's the obvious analogue to sendfile(2). I think it also requires two new VOPs, for efficiency, VOP_READ_MBUF (for sendfile) and VOP_WRITE_MBUF, which use an mbuf chain rather than uio to do their work. Perhaps at BSDCan, if this is my priority at the time. Or, if someone else wants to work on it I can provide patches that will require work. Thanks, matthew
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAMBSHm_eyksPRui2AWSbOBsU6==nSB5MHo6bvPPuOE1LPmvp8g>