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Message-ID: <41877.67.173.156.207.1196130992.squirrel@www.techfinesse.net> Date: Mon, 26 Nov 2007 20:36:32 -0600 (CST) From: bdupree@...hfinesse.com To: linux-kernel@...r.kernel.org Subject: Dynticks Causing High Context Switch Rate in ksoftirqd Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU on an idle system? The problem occurs if I config the kernel with tickless support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to "oprofile" for putting me onto this.) I have noted this same problem on kernel versions: 2.6.23.1, 2.6.23.8 and 2.6.23.9 ************************************************************************** *** Output from "vmstat -n 1 10" -- Note very high context switch rate *** *** This is on a idle machine! *** ************************************************************************** procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 0 1925556 4768 116104 0 0 124 2 6 7538 1 2 96 1 0 0 0 1925556 4768 116104 0 0 0 0 2 147329 0 1 99 0 0 0 0 1925548 4768 116104 0 0 0 0 0 154515 0 1 99 0 0 0 0 1925548 4768 116104 0 0 0 0 1 153898 0 2 98 0 0 0 0 1925548 4780 116104 0 0 0 16 3 155216 0 1 99 0 0 0 0 1925548 4780 116104 0 0 0 0 1 161718 0 1 99 0 0 0 0 1925548 4780 116104 0 0 0 0 0 147587 0 2 98 0 0 0 0 1925548 4780 116104 0 0 0 0 1 153524 0 2 98 0 0 0 0 1925448 4780 116104 0 0 0 0 0 153434 0 1 99 0 0 0 0 1925448 4792 116092 0 0 0 16 4 153527 0 2 98 0 ******************** *** System Stats *** ******************** Distro: Slackware 10.2 Mobo: MSI MasterX FA6R E7210 CPUs: Dual 2.4 GHz P4 Xeons 400 MHz FSB - Hyperthreading enabled Mem: 2 GB ECC DDR PC 266 ****************** *** PCI Config *** ****************** 00:00.0 Host bridge: Intel Corporation 82875P/E7210 Memory Controller Hub (rev 02) 00:03.0 PCI bridge: Intel Corporation 82875P/E7210 Processor to PCI to CSA Bridge (rev 02) 00:06.0 System peripheral: Intel Corporation 82875P/E7210 Processor to I/O Memory Interface (rev 02) 00:1c.0 PCI bridge: Intel Corporation 6300ESB 64-bit PCI-X Bridge (rev 02) 00:1d.0 USB Controller: Intel Corporation 6300ESB USB Universal Host Controller (rev 02) 00:1d.1 USB Controller: Intel Corporation 6300ESB USB Universal Host Controller (rev 02) 00:1d.4 System peripheral: Intel Corporation 6300ESB Watchdog Timer (rev 02) 00:1d.5 PIC: Intel Corporation 6300ESB I/O Advanced Programmable Interrupt Controller (rev 02) 00:1d.7 USB Controller: Intel Corporation 6300ESB USB2 Enhanced Host Controller (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 0a) 00:1f.0 ISA bridge: Intel Corporation 6300ESB LPC Interface Controller (rev 02) 00:1f.1 IDE interface: Intel Corporation 6300ESB PATA Storage Controller (rev 02) 00:1f.2 IDE interface: Intel Corporation 6300ESB SATA Storage Controller (rev 02) 00:1f.3 SMBus: Intel Corporation 6300ESB SMBus Controller (rev 02) 01:01.0 Ethernet controller: Intel Corporation 82547GI Gigabit Ethernet Controller 02:02.0 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI (rev 08) 03:09.0 Mass storage controller: Silicon Image, Inc. SiI 3114 [SATALink/SATARaid] Serial ATA Controller (rev 02) 03:0a.0 Ethernet controller: Intel Corporation 82541GI/PI Gigabit Ethernet Controller 03:0c.0 VGA compatible controller: ATI Technologies Inc Rage XL (rev 27) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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