On 09/26/2009 12:10 AM, ronnie sahlberg wrote: > On Fri, Sep 25, 2009 at 9:57 PM, FUJITA Tomonori > <fujita.tomonori@xxxxxxxxxxxxx> wrote: >> On Fri, 25 Sep 2009 14:39:59 +1000 >> ronnie sahlberg <ronniesahlberg@xxxxxxxxx> wrote: >> >>> You might find this tool useful. >>> I recently added very simple iscsi support to DBENCH ( http://dbench.samba.org ) >>> so that dbench has a minimal iscsi initiator built in. >>> >>> This is sometimes useful since it allows to bypass any iscsi initiator >>> layer, like open-iscsi, on the host and to get full control of exactly >>> what commands will be issued to the target and accurate measures since >>> one can know that the data was served across the network and not from >>> a local cache. >> >> Sounds interesting but you need to put the iscsi initiator feature >> into dbench? >> >> I mean that if dbench issues SCSI commands via sg from a load file, >> can you can achieve similar things? > > In theory yes. In practice no. > I could never reach very high workloads using the sg interface sg is stupidly slow because it does an head-of-queue insert of all commands. (What are you using write() or SG_IO?). head-of-queue inserts mean the queues are effectively flushed every time. bsg with the sg.flags = BSG_FLAG_Q_AT_TAIL and asynchronous operations should keep your queues full and saturate your network. (Without going through any cache) > but > using the iscsi backend to dbench I could easily generate 100s of > thousands of i/o per second. > I guess the queueing and i/o scheduling of the kernel comes in the way > and interferes. Yes, stupid sg driver see above Boaz > Using a tiny initiator built into dbench I avoid all interference from > the kernel. > (dbench can also generate I/O directly to a sd device) > >> >> >> btw, I got the latest code from the git tree, but seems that there is >> no iscsi support yet. >> > > > Oh, sorry about that. the webpage had a regression. > > The correct git tree is : > > git+ssh://git.samba.org/data/git/sahlberg/dbench.git > > Please try this tree. -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
