Messages in this thread | | | Date | Wed, 16 Mar 2016 09:26:31 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH RFC 0/2] mempool based chained scatterlist alloc/free api api |
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On Tue, Mar 15, 2016 at 04:12:03PM -0700, James Bottomley wrote: > motion. If you add in one patch and remove in another the code motion > trackers don't see it.
Agreed, having the move in a single patch would be nice.
> Thirdly, are you sure the pool structure for NVMe should be the same as > for SCSI? We don't do buddy pools for 1,2 or 4 entry transactions in > SCSI just basically because of heuristics, but the packetised io > characteristics of NVMe make single entry lists more likely for it, > don't they?
Not really. NVMe doesn't really do packetized I/O. And while people were setting all kinds of nomerge flags early on we're getting rid of them and are seeing similar I/O patterns to fast SCSI devices now.
NVMe over PCIe still uses the crazy PRPs by default, which aren't very suitable for this allocator (someone will have to come up with a good mempool for it eventually, though), but we're developing a set of new drivers transporting NVMe command which use SGLs very similar to most SCSI controllers, so using the same SGL allocator is a very natural choice.
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