On Wed, Aug 24, 2011 at 02:20:07PM +0800, Pekka Enberg wrote: > On Wed, Aug 24, 2011 at 9:06 AM, Stefan Priebe - Profihost AG > <s.priebe@xxxxxxxxxxxx> wrote: > > i hope this is the correct list to write to if it would be nice to give me a > > hint where i can ask. > > > > Kernel: 2.6.38 > > > > I'm seeing some strange problems on some of our servers after upgrading to > > 2.6.38. > > > > I'm copying a 1GB file via scp from Machine A to Machine B. When B is > > freshly booted the file transfer is done with about 80 to 85 Mb/s. I can > > repeat that various times to performance degrease. > > > > Then after some days copying is only done with about 900kb/s up to 3Mb/s > > going up and down while transfering the file. > > > > When i then do drop_caches it works again on 80Mb/s. > > > > sync && echo 3 >/proc/sys/vm/drop_caches && sleep 2 && echo 0 > >>/proc/sys/vm/drop_caches > > > > Attached is also an output of meminfo before and after drop_caches. > > > > What's going on here? MemFree is pretty high. > > > > Please CC me i'm not on list. > > Interesting. I can imagine one or more of the following to be > involved: networking, vmscan, block, and writeback. Lets CC all of > them! > > > # before drop_caches > > > > # cat /proc/meminfo > > MemTotal: 8185544 kB > > MemFree: 6670292 kB > > Buffers: 105164 kB > > Cached: 166672 kB > > SwapCached: 0 kB > > Active: 728308 kB > > Inactive: 567428 kB > > Active(anon): 639204 kB > > Inactive(anon): 394932 kB > > Active(file): 89104 kB > > Inactive(file): 172496 kB > > Unevictable: 2976 kB > > Mlocked: 2992 kB > > SwapTotal: 1464316 kB > > SwapFree: 1464316 kB > > Dirty: 52 kB > > Writeback: 0 kB Since dirty/writeback pages are low, it seems not being throttled by balance_dirty_pages(). Stefan, would you please run this several times on the server? ps -eo user,pid,tid,class,rtprio,ni,pri,psr,pcpu,vsz,rss,pmem,stat,wchan:28,cmd | grep scp It will show where the scp task is blocked (the wchan field). Hope it helps. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>