Date: Sun, 10 May 2015 18:46:49 +0530 From: Tinker <tinkr@openmailbox.org> To: Neel Natu <neelnatu@gmail.com> Cc: freebsd-virtualization@freebsd.org Subject: Re: Is the BHyVe guest as suitable for high-performance disk IO as the =?UTF-8?Q?host=3F?= Message-ID: <d1553f8bfaf28c2b13402c4c1f53c9dc@openmailbox.org> In-Reply-To: <CAFgRE9GZLXLOX%2BMyi7bPAU7uZPx5_6oSfrTj4RWPVGb-eYa3ZQ@mail.gmail.com> References: <7dd04a4cec612d18110a00b9020fd948@openmailbox.org> <CAFgRE9GZLXLOX%2BMyi7bPAU7uZPx5_6oSfrTj4RWPVGb-eYa3ZQ@mail.gmail.com>
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Hi Neel, Thank you very much for your response - That's great! I guess this should deliver the full capacity for basically any IO system around, be it a fast SSD or ramdisk. (Since the guest may not need to flush data immediately to the host, I guess read performance is the more sensitive point.) Which disk emulation mode is best for a BSD guest, "virtio-blk" or "ahci-hd"? In general, should any other consideration be made for performance (using the "direct" or "nocache" BHyVe configuration options, particular consideration for proper sector alignment when using a disk image stored on the host's SSD-based ZFS, mounting the host ZFS filesystem with "noatime")? Kind regards, Tinker On 2015-05-10 04:03, Neel Natu wrote: > Hi Tinker, > > On Sat, May 9, 2015 at 9:49 AM, Tinker <tinkr@openmailbox.org> wrote: >> Hi! >> >> For an environment with very heavy parallell IO, should the >> performance be >> just as good in a BHyVe guest as in the FreeBSD host environment? >> >> What I thought of is that I guess within the host environment, the >> storage >> subsystem should have all kinds of optimizations like an internal work >> queue >> that pushes lots of work alinearly/asynchronously to the disk >> controller and >> this way allows it, in turn, to give all its performance. >> >> Does the virtualized disk interface carry over all that goodness to >> the >> guest? >> > > bhyve creates 8 worker threads for each virtual disk controller (both > ahci and virtio-blk). > > All guest I/O is handled asynchronously by these worker threads which > provide parallelism. > >> (https://wiki.freebsd.org/bhyve seems to say yes, presuming you >> configure >> BHyVe to run the virtual disk in AHCI mode?) >> > > The wiki is out of date. > > Since r280037 the virtio-blk emulation also gets the benefits of using > the block_if worker threads. > > best > Neel > >> Thanks! >> Tinker >> >> _______________________________________________ >> freebsd-virtualization@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization >> To unsubscribe, send any mail to >> "freebsd-virtualization-unsubscribe@freebsd.org"
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