* storage: share the volume strings a cluster repeats
Decoding a heartbeat allocates a fresh string for the collection, disk type and
remote backend of every volume, and a master holding a million volumes then
holds a million copies of the same handful of names.
Not the remote storage key, which is unique per volume: interning that would
fill the table rather than share anything.
800k volumes registered from a heartbeat that has actually been over the wire:
227 -> 211 B/volume, and 238 -> 214 when the volumes are tiered, since the
backend name shares too.
* storage: hold the interned strings rather than let them be collected
unique.Make clears its entries by weak reference, and its canonical value does
not survive a collection even while a caller still holds the string it handed
back -- so a volume reported later would get a second copy of a name the rest
of the cluster already shares. With only changed volumes reported, most are
interned once and never again, so that is the common case rather than a corner.
The table therefore only grows, which is why it stays restricted to values
drawn from a small set. Ten thousand collections keep a few hundred kilobytes.
Chris LuandGitHub
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