(adding netdev cc:) On 8/4/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > On Sat, 4 Aug 2007, Ingo Molnar wrote: > > > * Ingo Molnar <[EMAIL PROTECTED]> wrote: > > > >> There are positive reports in the never-ending "my system crawls like > >> an XT when copying large files" bugzilla entry: > >> > >> http://bugzilla.kernel.org/show_bug.cgi?id=7372 > > > > i forgot this entry: > > > > " We recently upgraded our office to gigabit Ethernet and got some big > > AMD64 / 3ware boxes for file and vmware servers... only to find them > > almost useless under any kind of real load. I've built some patched > > 2.6.21.6 kernels (using the bdi throttling patch you mentioned) to > > see if our various Debian Etch boxes run better. So far my testing > > shows a *great* improvement over the stock Debian 2.6.18 kernel on > > our configurations. " > > > > and bdi has been in -mm in the past i think, so we also know (to a > > certain degree) that it does not hurt those workloads that are fine > > either. > > > > [ my personal interest in this is the following regression: every time i > > start a large kernel build with DEBUG_INFO on a quad-core 4GB RAM box, > > i get up to 30 seconds complete pauses in Vim (and most other tasks), > > during plain editing of the source code. (which happens when Vim tries > > to write() to its swap/undo-file.) ] > > I have an issue that sounds like it's related. > > I've got a syslog server that's got two Opteron 246 cpu's, 16G ram, 2x140G > 15k rpm drives (fusion MPT hardware mirroring), 16x500G 7200rpm SATA > drives on 3ware 9500 cards (software raid6) running 2.6.20.3 with hz set > at default and preempt turned off. > > I have syslog doing buffered writes to the SCSI drives and every 5 min a > cron job copies the data to the raid array. > > I've found that if I do anything significant on the large raid array that > the system looses a significant amount of the UDP syslog traffic, even > though there should be pleanty of ram and cpu (and the spindles involved > in the writes are not being touched), even a grep can cause up to 40% > losses in the syslog traffic. I've experimented with nice levels (nicing > down the grep and nicing up the syslogd) without a noticable effect on the > losses. > > I've been planning to try a new kernel with hz=1000 to see if that would > help, and after that experiment with the various preempt settings, but it > sounds like the per-device queues may actually be more relavent to the > problem. > > what would you suggest I test, and in what order and combination?
At least on a surface level, your report has some similarities to http://lkml.org/lkml/2007/5/21/84 . In that message, John Miller mentions several things he tried without effect: < - I increased the max allowed receive buffer through < proc/sys/net/core/rmem_max and the application calls the right < syscall. "netstat -su" does not show any "packet receive errors". < < - After getting "kernel: swapper: page allocation failure. < order:0, mode:0x20", I increased /proc/sys/vm/min_free_kbytes < < - ixgb.txt in kernel network documentation suggests to increase < net.core.netdev_max_backlog to 300000. This did not help. < < - I also had to increase net.core.optmem_max, because the default < value was too small for 700 multicast groups. As they're all pretty simple to test, it may be worthwhile to give them a shot just to rule things out. Ray - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
