On Fri, Aug 08, 2014 at 01:06:15AM -0400, Oleg Drokin wrote: > > On Aug 8, 2014, at 12:42 AM, Greg Kroah-Hartman wrote: > > > On Fri, Aug 08, 2014 at 12:03:20AM -0400, Oleg Drokin wrote: > >> Hello! > >> > >> On Aug 7, 2014, at 11:49 PM, Greg Kroah-Hartman wrote: > >>>> > >>>> This is not a critical bug and in the worst case the code here may > >>>> cause miss of statistics counter increase. > >>>> This is why I think it is not worth to backport the patch at all. > >>> You are right, and if this is just for some random "statistics" file, > >>> can we just delete the whole function? > >> > >> I hope not! > >> This is used all around the client to tally up various operations executed counts. > > Why would you do that? Why would they care? > > We would do that to provide information on the client operations performed. > They would care because they are interested in what particular clients might be doing. > > >> The statistic is then used by various userspace monitoring tools. > > Why not use the in-kernel monitoring tools instead of creating your own? > > What does userspace do with that information? > > We don't really control the userspace tools. People write tools to suit their needs > to monitor loads, see odd things the end users are doing or possibly for some > debugging even. > Correlating these numbers with what server sees also proves useful at times > (write combining for example). > > Here's a sample of output of a recently mounted client that I poked on a bit (the lines starting with # are my comments): > # cat /proc/fs/lustre/llite/lustre-ffff88008dde27f0/stats > snapshot_time 1407473168.466102 secs.usecs > read_bytes 1 samples [bytes] 0 0 0 > write_bytes 4 samples [bytes] 2 7 19 > osc_write 4 samples [bytes] 2 7 19 > # The bytes counts show you minimum, maximum of writes seen and total number of bytes read-written. > # Lustre (and many other network filesystems) is very sensitive to small IO, esp. reads so it's good > # to know if you have a lot of it. > open 6 samples [regs] > # The "regs" type just shows you how many of given type operations were performed since last statistic reset. > # Frequently that allows people to guess where does high load come from on a particular client when > # it's otherwise not obvious because not a lot of cpu is used. > # Some operations are heavier than others too. > close 6 samples [regs] > readdir 4 samples [regs] > setattr 1 samples [regs] > truncate 4 samples [regs] > getattr 7 samples [regs] > create 1 samples [regs] > alloc_inode 1 samples [regs] > getxattr 8 samples [regs] > inode_permission 28 samples [regs] > > As more operations types are seen the list grows. > Then there are also specific stats for readahead (data and metadata) so that interested people can make informed > decisions on the tuning there should they be unsatisfied with default settings. > > I am not sure there's a similar mechanism in the kernel already that > would allow us to get this sort of data easily all in one place? perf should show you this, if not, please add the functionality there. A filesystem is not the place to have performance monitoring code, this needs to be removed before it can be moved out of staging. Please work with the trace/perf developers on this if there is something lacking there. thanks, greg k-h dG > > Bye, > Oleg _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
