On Tue, Oct 13, 2015 at 01:39:13AM +0000, Al Lau (alau2) wrote: > Have a 3 TB file. Logically divide into 1024 sections. Each > section has a process doing dd to a randomly selected 4K block in > a loop. Will this test case eventually cause the extent > fragmentation that lead to the kmem_alloc message? > > dd if=/var/kmem_alloc/junk of=/var/kmem_alloc/fragmented obs=4096 bs=4096 count=1 seek=604885543 conv=fsync,notrunc oflag=direct If you were loking for a recipe to massively fragment a file, then you found it. And, yes, when you start to get millions of extents in a file such as this workload will cause, you'll start having memory allocation problems. But I don't think that sets the GFP_ZERO flag anywhere, so that's not necessarily where the memroy shortage is coming from. I just committed some changes to the dev tree that allow for more detailed information from this allocation error point to be obtained - perhaps if woul dbe worthwhile trying a kernel build form the current for-next tree and turning the error level up to 11? Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
