Quoting Dave Chinner (2013-06-14 22:50:50) > From: Dave Chinner <dchinner@xxxxxxxxxx> > > Doing writeback on lots of little files causes terrible IOPS storms > because of the per-mapping writeback plugging we do. This > essentially causes imeediate dispatch of IO for each mapping, > regardless of the context in which writeback is occurring. > > IOWs, running a concurrent write-lots-of-small 4k files using fsmark > on XFS results in a huge number of IOPS being issued for data > writes. Metadata writes are sorted and plugged at a high level by > XFS, so aggregate nicely into large IOs. However, data writeback IOs > are dispatched in individual 4k IOs, even when the blocks of two > consecutively written files are adjacent. > > Test VM: 8p, 8GB RAM, 4xSSD in RAID0, 100TB sparse XFS filesystem, > metadata CRCs enabled. > > Kernel: 3.10-rc5 + xfsdev + my 3.11 xfs queue (~70 patches) I'm a little worried about this one, just because of the impact on ssds from plugging in the aio code: https://lkml.org/lkml/2011/12/13/326 How exactly was your FS created? I'll try it here. -chris -- 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
