Instead move to a threading model like the Windows one.
We'll queue several work items to be executed in a system thread (Cc worker)
when there are VACB that have been marked as dirty. Furthermore, some delay
will be observed before action to avoid killing the system with IOs.
This new threading model opens way for read ahead and write behind implementation.
Also, moved the initialization of the lazy writer to CcInitializeCacheManager()
it has nothing to do with views and shouldn't be initialized there.
Also, moved the lazy writer implementation to its own file.
Modified CcDeferWrite() and CcRosMarkDirtyVacb() to take into account the new threading model.
Introduced new functions:
- CcPostWorkQueue(): post an item to be handled by Cc worker and spawn a worker if required
- CcScanDpc(): called after some time (not to have lazy writer always running) to queue a lazy scan
- CcLazyWriteScan(): the lazy writer we used to have
- CcScheduleLazyWriteScan(): function to call when you want to start a lazy writer run. It will make a DPC after some time and queue execution
- CcWorkerThread(): the worker thread that will handle lazy write, read ahead, and so on
This removes the "modified page writer" thread in Mm that was regularly blindly
attempting to flush dirty pages to the disk.
Instead, this commit introduces a lazy writer that will monitor dirty pages count
and will flush them to disk when this count is above a threshold. The threshold is
computed on Cc init.
Compared to what was done previously, this lazy writer will only write down files
that are not marked as temporary.
The mechanisms involved in this lazy writer worker are well described in Windows
Internals 4th editions (constants are coming from it ;-)).
Also fixed a bad (and old!) bug in CcRosFlushDirtyPages() where target count could
be overflow and the function would spin forever while holding the VACBs lock. This is
mandatory as now lazy writer will call it with "random" values.
This also allows implementing CcWaitForCurrentLazyWriterActivity() :-).
Also renamed DirtyPageCount to its MS equivalent.
CORE-14235
