Messages in this thread | | | Date | Fri, 2 Sep 2011 09:08:35 -0400 | From | Ted Ts'o <> | Subject | Re: Approaches to making io_submit not block |
| |
On Thu, Sep 01, 2011 at 04:54:15PM +1000, Dave Chinner wrote: > Apples to oranges - there's orders of magnitude of difference in the > number of operations that the different stacks do. Allocation in XFS > when it does not block can still take milliseconds of CPU time; in > comparison, the networking stack is expected to process thousands of > packets in that same time frame. IOWs, the scale of processing per > item of work is -vastly- different - that's why working in process > context matters a great deal to the networking stack but not to > allocation in XFS.
That may be true for hard drives, but PCIe attached flash can support millions of IOP's per second --- i.e., at least hundreds of IOP's in milliseconds. Yes, these devices are expensive, but so are the thousand-disk RAID arrays that some people attach via XFS. :-)
There are people in the ext4 development community interested in looking at such devices. We've made some improvements, we (and by this I mean the whole kernel) are a long, long way from supporting such beasts properly....
- Ted
| |