On 04/24/2014 02:25 PM, Matthew Wilcox wrote:
On Thu, Apr 24, 2014 at 11:10:09AM -0700, Purush Gupta wrote:
That would require a new NVMe write command semantic with descriptors
currently its not there.
Yes ... I don't want to start defining such a command on linux-fsdevel.
What I'm hearing is that there's no benefit to a device that can guarantee
to write multiple contiguous sectors in a non-torn manner over a device
that can write a single sector in a non-torn manner.
For any real benefit, filesystems need (and Linux needs to introduce
plumbing for) vectored atomic writes.
That's my feeling. The non-vectored use case is pretty limited, mostly
to help get a contiguous log entry on disk as a full unit. But most of
the time the filesystem log commits are pretty big. Workloads with a
very small number of latency sensitive writers would see improvements.
We could also the contiguous atomics for something like mysql by using a
16K sector size in the filesystem. At that point all of the db 16K
units will be contig and the existing atomics proposals become interesting.
But I was really hoping for the vectors ;)
-chris
--
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
