[ add CC ] On Sun, Sep 16, 2012 at 08:26:04AM -0400, Namjae Jeon wrote: > From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx> > > This commit adds dirty_background_centisecs description in bdi sysfs > documentation. > > Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx> > Signed-off-by: Vivek Trivedi <t.vivek@xxxxxxxxxxx> > --- > Documentation/ABI/testing/sysfs-class-bdi | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi > index 5f50097..6869736 100644 > --- a/Documentation/ABI/testing/sysfs-class-bdi > +++ b/Documentation/ABI/testing/sysfs-class-bdi > @@ -48,3 +48,28 @@ max_ratio (read-write) > most of the write-back cache. For example in case of an NFS > mount that is prone to get stuck, or a FUSE mount which cannot > be trusted to play fair. > + > +dirty_background_centisecs (read-write) > + > + It is used to start early writeback of given bdi once bdi dirty > + data exceeds product of average write bandwidth and > + dirty_background_centisecs. It works in parallel of > + dirty_writeback_centsecs and dirty_expire_interval based periodic > + flushing mechanism. > + > + It is mainly useful for tuning writeback speed at 'NFS Server' > + sothat NFS client could see better write speed. > + A good use case is setting it to around 100 (1 second) in the NFS > + server for improving NFS write performance. Note that it's not > + recommended to set it to a too small value, which might lead to > + unnecessary flushing for small IO size. > + Setting it to 0 disables the feature. > + > + However, sometimes it may not match user expectations as it is based > + on bdi write bandwidth estimation. The users should not expect this > + threshold to work accurately. > + Write bandwidth estimation is a best effort to estimate bdi write > + speed bandwidth. But it can be wildly wrong in certain situations > + such as sudden change of workload (including the workload startup > + stage), or if there are no heavy writes since boot, in which case > + there is no reasonable estimation yet. > -- > 1.7.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>