Patch #1 sets up some helper functions for accounting. Patch #2 adds writeback files for visibility To help developers and applications gain visibility into writeback behaviour adding two read-only sysctl files into /proc/sys/vm. These files allow user apps to understand writeback behaviour over time and learn how it is impacting their performance. # cat /proc/sys/vm/pages_dirtied 3747 # cat /proc/sys/vm/pages_entered_writeback 3618 These two new files are necessary to give visibility into writeback behaviour. We have /proc/diskstats which lets us understand the io in the block layer. We have blktrace for more in depth understanding. We have e2fsprogs and debugsfs to give insight into the file systems behaviour, but we don't offer our users the ability understand what writeback is doing. There is no way to know how active it is over the whole system, if it's falling behind or to quantify it's efforts. With these values exported users can easily see how much data applications are sending through writeback and also at what rates writeback is processing this data. Comparing the rates of change between the two allow developers to see when writeback is not able to keep up with incoming traffic and the rate of dirty memory being sent to the IO back end. This allows folks to understand their io workloads and track kernel issues. Non kernel engineers at Google often use these counters to solve puzzling performance problems. Michael Rubin (2): mm: helper functions for dirty and writeback accounting writeback: Adding pages_dirtied and pages_entered_writeback Documentation/sysctl/vm.txt | 20 +++++++++++++++--- drivers/base/node.c | 14 +++++++++++++ fs/ceph/addr.c | 8 +----- fs/nilfs2/segment.c | 2 +- include/linux/mm.h | 1 + include/linux/mmzone.h | 2 + include/linux/writeback.h | 9 ++++++++ kernel/sysctl.c | 14 +++++++++++++ mm/page-writeback.c | 45 ++++++++++++++++++++++++++++++++++++++++-- mm/vmstat.c | 2 + 10 files changed, 103 insertions(+), 14 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
