Flash device vendors are coming up with faster and faster devices every year. Given the high performance supported by these devices, there are thoughts about using them not only as high performance storage but also as a replacement for huge quantities of DRAM. That particular use case would put very stringent requirements on the performance of file systems on these devices --- an issue that should be discussed. I will share our experience running some experiments on a high performance flash device (FusionIO IODrive duo) with ext4 and XFS. We have devised an extensive set of experiments focused on finding the scaling and overhead problems in the kernel. Our experiments use various IO sizes, and perform IO in both synchronous multi-threaded mode and AIO mode. We configure our setup to bypass the block layer (fusionIO driver supports that), and do IO in O_DIRECT mode to minimize overhead in the kernel. In spite of such optimizations, we still see performance issues especially while doing IO at the peak throughput capacity available on these drives. The issues pertain to CPU scheduling behavior, filesystem metadata manipulation, and basically the whole kernel code path involved in doing IO to such devices, that would not be involved if data was read from DRAM directly. -- Nauman -- 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
