Namespace performance acceleration by selective SSD caching

1. A non-transitory storage medium having stored therein computer-executable instructions which, when executed by one or more hardware processors, perform the following processes:

receiving metadata in the form of a modification to metadata represented by a file system namespace abstraction, wherein the file system namespace abstraction corresponds to less than an entire file system namespace;

updating the file system namespace abstraction based on the received metadata;

determining if caching is enabled for the file system namespace abstraction; and

when caching is enabled for the file system namespace abstraction, caching the updated file system namespace abstraction in SSD storage.

2. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction is in the form of an Mtree.

3. The non-transitory storage medium as recited in claim 2 , wherein the Mtree is included in a file system namespace that also includes another Mtree for which caching is not enabled.

4. The non-transitory storage medium as recited in claim 1 , wherein when caching is not enabled for the file system namespace abstraction, the updated file system namespace abstraction is not cached in the SSD storage.

5. The non-transitory storage medium as recited in claim 1 , wherein when caching is enabled for the file system namespace abstraction, the updated file system namespace abstraction is cached in SSD storage in the form of a flattened Btree.

6. The non-transitory storage medium as recited in claim 5 , wherein the flattened Btree includes one or more pages.

7. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction represents a portion of a file system.

8. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction is in the form of an Mtree, and the processes further comprise defragmenting the SSD storage by removing cached metadata that corresponds with a deleted Mtree.

9. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction is in the form of an Mtree, and the processes further comprise allocating a respective specific amount of SSD storage to each of a plurality of Mtrees.

10. A physical device, wherein the physical device comprises:

one or more hardware processors; and

the non-transitory storage medium as recited in claim 1 .

11. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction is in the form of an Mtree, and the processes further comprise disabling caching for the Mtree.

12. The non-transitory storage medium as recited in claim 11 , wherein the processes further comprise performing a defragmentation process by throwing away cached pages corresponding to the disabled Mtree.

13. The non-transitory storage medium as recited in claim 12 , wherein the defragmentation process is performed according to an allocation of SSD storage.

14. The non-transitory storage medium as recited in claim 12 , wherein the defragmentation process is performed based on page header time stamps.

15. The non-transitory storage medium as recited in claim 1 , wherein the file system namespace abstraction is in the form of an Mtree, and the processes further comprise controlling allocation of SSD storage to each of a plurality of Mtrees, wherein the allocation is based on a weighting scheme.