[EMAIL PROTECTED] wrote on Wed, 05 Mar 2008 16:08 +0200: > Pete Wyckoff wrote: > > [EMAIL PROTECTED] wrote on Sun, 02 Mar 2008 15:17 +0200: > >> 27920 tgtd: [16:40:38.907895] iscsi_scsi_cmd_tx_done(1707) more data or > >> sense or bidir b > >> 27921 tgtd: [16:40:38.908269] iser_rx_progress(1101) entry > > > > This is rather slow in here. It does the RDMA write, gets the local > > completion that the write went out, then sends the command response > > packet. Does it make sense that it takes 374 us for the adapter to > > say that it finished the write? > > > > Where did you get the 374 us from?
Subtracting the times on the above two lines. Just an idea for where you might go to look for performance. > > Another comment: there is 10 us between consecutive printfs in this > > trace. You're probably not using TSC for GTOD. It's not a big > > deal, but be aware that your "with debugging" runs may be > > significantly slower than without. > > That's for sure. However, I tried to run without debugging, and > host_busy was <= 1. > > > Just watch to make sure that the > > profiling output makes sense. We hack the kernel in a bad way to > > get around this on our machines. > > http://git.osc.edu/?p=linux.git;a=commitdiff;h=e7ff54222523a2ae6816c9ff17ad5a8fa86cd5e1 > > > > What does this patch do? I'm not familiar with that. Just ignore it. Hardware-specific way to force the use of TSC. > According to this patch, bs_rdwr_request will be called from the context > of iser_rx_progress (sounds good). Why doesn't the current stgt code do > that? Why do we need the extra context switch? That's the only way to get multi-operation concurrency on the target given existing linux userspace AIO infrastructure: run multiple IOs at the same time, in separate threads. The patch I sent you is just so you can debug, to answer the question: Is the context switch the source of your performance problem on a _single_ request. -- Pete _______________________________________________ Stgt-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/stgt-devel
