On 03/25/2013 09:48 PM, Dan McDonald wrote: > On Mon, Mar 25, 2013 at 09:43:31PM +0100, Sa?o Kiselkov wrote: >> On 03/25/2013 06:39 PM, Franz Schober wrote: >>> Hi, >> >> A bunch more things came to my mind, see comments below: >> >>> Test: Writing a 1 GB File >>> time dd if=/dev/zero of=/tmp/testfile1 bs=128k count=8k >>> Mean value of 3 tests on every system. >>> (I also tried IOZone but the simple dd test seems to show the problem) >> >> Make sure you write a lot more data per test run. Give it like 50-60GB >> at least. Btw: "/tmp" is tmpfs, which resides on your swap device, which >> is decided not a high-performance file system store. > > /tmp is memory first, and if there's no swap device, it uses available system > memory. > > I *thought* that's what the original poster was decrying, his memory > throughput, as measured via in-memory tmpfs.
I understand that that's what his issue was, however, I'm not aware of tmpfs having been designed with hundreds of MB/s of throughput in mind... If he wants to test raw memory throughput, why not simply created a ramdisk (ramdiskadm) and do a dd to it? Heck of a lot thinner in number of layers you need to traverse before you hit the VM layer. Plus, tmpfs isn't pre-allocated, it eats pages from the disk pagelist, possibly contending with the ZFS ARC. In short, if a VM test is needed, ramdisk is a lot simpler to manage than tmpfs. -- Saso ------------------------------------------- illumos-discuss Archives: https://www.listbox.com/member/archive/182180/=now RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be Modify Your Subscription: https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4 Powered by Listbox: http://www.listbox.com
