[openstack-dev] leverage page cache in openstack swift

Clay Gerrard clay.gerrard at gmail.com
Fri Oct 6 23:10:29 UTC 2017


There's a couple of options in the object server that are related to how
object data is cached (or generally *not*)

https://github.com/openstack/swift/blob/master/swift/obj/server.py#L921

At scale on dense nodes it becomes challenging to keep all the filesystem
metdata in the page cache, so we've tried a few different tricks and
tunings over the years to optimize towards using as much RAM as possible on
minimizing the number of seeks "wasted" to pickup filesystem directory and
extent information instead of object data.  BUT on nodes with more RAM and
less objects (or fewer *active* objects) it is definitely possible to tune
towards keeping more object data in the page cache.

Good luck!

-Clay


On Fri, Oct 6, 2017 at 2:34 PM, Jialin Liu <jalnliu at lbl.gov> wrote:

> Hi,
> Is there any existing work that leveraging operating system's page cache
> for swift?
> like many other parallel file systems, lustre, the IO is cached in buffer
> and call is returned immediately to user space.
>
> Best,
> Jialin
>
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