Hi Pavlov, Thanks for your explanation. However, I still have these questions:
1. If locking is per page-level and there are no entry-level locks, then why does the documentation here talk about having entry-level transaction locks? https://apacheignite.readme.io/docs/transactions 2. I'm not clear with what "locking a durable memory region segment " means, what is a segment? Does a page contain multiple segments or a segment contains multiple pages? The mental picture I have is: a memory region is divided into pages (which can be meta data pages, index, or data pages). Index pages hold links to data page id and offset for key-value pairs while data pages contain the actual key-value pairs. So, what really is a segment and what does locking a memory segment means? I understanding page-locks, what is segment lock? Appreciate your response!!! On Tue, Feb 13, 2018 at 2:32 AM, Dmitry Pavlov <dpavlov....@gmail.com> wrote: > Hi John, > > 1. No, content modification require lock holding to page to provide > consitency in multithreaded environment. > 2. Page is locked for read before reading its content, and unlocked after. > Same for lock for write for writting. 1 writer or N readers allowed for > page. On unlock write lock, dirty flag for page may be set if there data > was actually modified. > 3. Lock has per-page basis, additional striping by any offest within page > is not required accoring to tests. > > Only one contention is observed sometimes in high load test, it is > contention of threads to lock to durable memory region segment. But this > situation can be handled by setting concurrenclyLevel in > DataStorageConfiguration. > > Sincerely, > Dmitriy Pavlov > > > вт, 13 февр. 2018 г. в 9:56, John Wilson <sami.hailu...@gmail.com>: > > > Hi, > > > > Ignite documentation talks about entry-level locks and the page structure > > has a LOCK_OFFSET that I assume is used to store tag info. I have these > > questions. > > > > 1. Does Ignite use a lock-free implementation to lock pages and/or > > entries? > > 2. When is a page locked and when is it released? > > 3. When an entry is inserted/modified in a page, is the page locked > > (forbidding other threads from inserting entries in the page)? or only > > the > > entry's offset is locked? (allowing other threads to insert/modify > other > > items) > > > > Thanks! > > >
