>>>>> "Dave" == Dave Chinner <david@xxxxxxxxxxxxx> writes: >> Agreed. I too am curious to study which circumstances favor copying >> vs blocking. Dave> IMO blocking is generally preferable in high throughput threaded Dave> workloads as there is always another thread that can do useful Dave> work while we wait for IO to complete. Most use cases for DIF Dave> center around high throughput environments.... Yeah. A while back I did a bunch of tests with a liberal amount of wait_on_page_writeback() calls added to (I think) ext2, ext3, and XFS. For my regular workloads there was no measurable change (kernel builds, random database and I/O tests). I'm sure we'll unearth some apps that will suffer when DI is on but so far I'm not too worried about blocking in the data path. My main concern is wrt. metadata because that's where extN really hurts. Simple test: Unpack a kernel tarball and watch the directory block fireworks. Given how frequently those buffers get hit I'm sure blocking would cause performance to tank completely. I looked into fixing this in ext2 but I had to stop because my eyes were bleeding. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
