On Thu, 2013-10-03 at 09:16 -0500, Xianghua Xiao wrote: > The IRQ is balanced to all cores(cat /proc/interrupts), the option is > turned on via menuconfig. Still the performance is the same. > Please don't top-post. It makes it annoying to respond to what's already been said in the thread. FYI, there is no kernel option to balance IRQs automatically across CPUs, it's done via userspace using irqbalanced, or via explicit settings in /proc/irq/$IRQ/smp_affinity_list. So, I'd still like to see your /proc/interrupts output in order to determine the distribution. Some top and perf top output would be useful as well to see what processes and functions are running. > The emulate_write_cache=1 did not help performance either. > > How does LIO/iscsi handle multi-thread on multi-core system? > As explained below: So target_core_mod uses a bounded workqueue for it's I/O completion, which means that process context is provided on the same CPU for which the hardware interrupt was generated in order to benefit from cache locality effects. If all of the hardware interrupts for the entire system are firing only on CPU0, then only kworkerd/0 is used to provide process context for queuing the response to the fabric drivers. Also, I can confirm with v3.11 code that iscsi-target is running dual port ixgbe line rate (~20 Gb/sec) with large block reads/writes to PCIe flash, and to ramdisk_mcp backends. So that said, I'll need more information about your setup to determine what's going on. --nab -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
