protect sync with a lock #309
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This avoid multiple readers modifying the state concurrently.
icristescu
approved these changes
Apr 28, 2021
samoht
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Apr 29, 2021
CHANGES: ## Fixed - Reduce allocations during merge (mirage/index#274, mirage/index#277) - Protect concurrent syncs with a lock (mirage/index#309) - Fixed a performance issue for `Index.sync` when there is a blocking merge in progress: the `log_async` file was not cached properly and fully reloaded from disk every time. (mirage/index#310) - Release the merge lock if a merge raises an exception (mirage/index#312) - Added fsync after `Index.clear` to signal more quickly to read-only instances than something has changed in the file (mirage/index#308) ## Changed - Specialise `IO.v` to create read-only or read-write instances. (mirage/index#291) - `clear` removes the files on disks and opens new ones containing only the header. (mirage/index#288, mirage/index#307, mirage/index#317)
samoht
added a commit
to samoht/opam-repository
that referenced
this pull request
Apr 29, 2021
CHANGES: ## Fixed - Reduce allocations during merge (mirage/index#274, mirage/index#277) - Protect concurrent syncs with a lock (mirage/index#309) - Fixed a performance issue for `Index.sync` when there is a blocking merge in progress: the `log_async` file was not cached properly and fully reloaded from disk every time. (mirage/index#310) - Release the merge lock if a merge raises an exception (mirage/index#312) - Added fsync after `Index.clear` to signal more quickly to read-only instances than something has changed in the file (mirage/index#308) ## Changed - Specialise `IO.v` to create read-only or read-write instances. (mirage/index#291) - `clear` removes the files on disks and opens new ones containing only the header. (mirage/index#288, mirage/index#307, mirage/index#317)
samoht
added a commit
to samoht/opam-repository
that referenced
this pull request
Apr 29, 2021
CHANGES: ## Fixed - Reduce allocations during merge (mirage/index#274, mirage/index#277) - Protect concurrent syncs with a lock (mirage/index#309) - Fixed a performance issue for `Index.sync` when there is a blocking merge in progress: the `log_async` file was not cached properly and fully reloaded from disk every time. (mirage/index#310) - Release the merge lock if a merge raises an exception (mirage/index#312) - Added fsync after `Index.clear` to signal more quickly to read-only instances than something has changed in the file (mirage/index#308) ## Changed - Specialise `IO.v` to create read-only or read-write instances. (mirage/index#291) - `clear` removes the files on disks and opens new ones containing only the header. (mirage/index#288, mirage/index#307, mirage/index#317)
samoht
added a commit
to samoht/opam-repository
that referenced
this pull request
Apr 29, 2021
CHANGES: - Reduce allocations during merge (mirage/index#274, mirage/index#277) - Protect concurrent syncs with a lock (mirage/index#309) - Fixed a performance issue for `Index.sync` when there is a blocking merge in progress: the `log_async` file was not cached properly and fully reloaded from disk every time. (mirage/index#310) - Release the merge lock if a merge raises an exception (mirage/index#312) - Added fsync after `Index.clear` to signal more quickly to read-only instances than something has changed in the file (mirage/index#308) - Specialise `IO.v` to create read-only or read-write instances. (mirage/index#291) - `clear` removes the files on disks and opens new ones containing only the header. (mirage/index#288, mirage/index#307, mirage/index#317)
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This avoid multiple readers modifying the state concurrently.
Note: I am not sure it's a real issue, but as this is the only function modifying
t.generationt.logandt.log_asyncfor read-only instances, so it's probably a good idea to make sure we do this safely. We need to see the performance implication as now all the concurrent sync calls will be gated on that lock.