This halfplements CcScheduleReadAhead() which is responsible for finding the next reads
to perform given last read and previous reads. I made it very basic for now, at least
to test the whole process.
This also introduces the CcExpressWorkQueue in the lazy writer which is responsible
for dealing with read ahead items and which is dealt with before the regular queue.
In CcCopyData(), if read was fine, schedule read ahead so that it can happen in background
without the FSD to notice it! Also, update the read history so that scheduling as a
bit of data.
Implement (à la "old Cc" ;-)) CcPerformReadAhead() which is responsible for performing
the read. It's only to be called by the worker thread.
Side note on the modifications done in CcRosReleaseFileCache(). Private cache map
is tied to a handle. If it goes away, private cache map gets deleted. Read ahead
can run after the handle was closed (and thus, private cache map deleted), so
it is mandatory to always lock the master lock before accessing the structure in
read ahead or before deleting it in CcRosReleaseFileCache(). Otherwise, you'll
just break everything. You've been warned!
This commit also partly reverts f8b5d27.
CORE-14312
We get rid of the old iLazyWriterNotify event in favor of work items
that contain an event that lazy writer will set once its done.
To implement this, we rely on the newly introduced CcPostTickWorkQueue work queue
that will contain work items that are to be queued once lazy writer is done.
Move the CcWaitForCurrentLazyWriterActivity() implementation to the
lazy writer file, and reimplemented it using the new support mechanisms
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 means that MmSystemCacheStart, MmSystemCacheEnd, MmSizeOfSystemCacheInPages
have now a valid value.
System cache is not used atm the moment though. MmMapViewInSystemCache() is to
be implemented, and Cc is to be made aware of this.
CORE-14259
- Change MM_SYSTEM_SPACE_START to 0xFFFFF88000000000
- Move MI_DEBUG_MAPPING to the end of the system PTE range
- Add MI_SYSTEM_CACHE_START and MI_SYSTEM_CACHE_END, which is in the range that Vista uses as dynamic VA space for cache and other allocations
- Wrap x86 specific code that makes now invalid assumptions about the address space layout in #ifdef _M_IX86
Namely, implement CcSetDirtyPageThreshold() and add support for it
in CcCanIWrite().
Also added my name in the headers of the few files I touched tonight.
CORE-14235
Namely, implement CcCanIWrite() (very basic, and likely wrong).
And implement CcDeferWrite() which will queue the write operation.
In CciLazyWriter() (which may be renamed CcWorkerThread() ;-)),
handle the queued write operations one by one. This is likely
not to be accurate, but, given we have only on FS supporting
this for now (NFS / RDBSS / Shares), this is OK.
CORE-14235
Experiment and MSDN tend to show that a dirty BCB is queued for lazy write.
This will do the job here!
Also, renamed CcRosMarkDirtyFile() which is more accurate, and added a new
function CcRosMarkDirtyVacb() which just takes a VACB as arg (expected locked)
and marks it dirty (using previous implementation). Make CcRosMarkDirtyFile()
use it.
CORE-14235
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
Note: before we had a BOOLEAN parameter called StoreInstruction, but in reality it was not specifying whether the fault was from a store store instruction, but whether it was an access violation rather than a page-not-present fault. On x86 without PAE there are only 2 kinds of access violations: (1) Access of a kernel mode page from user mode, which is handled early and (2) access of a read-only (or COW) page with a writing instruction. Therefore we could get away with this, even though it relied on the wrong assumption that a fault, which was not a page-not-present-fault, was automatically a write access. This commit only changes one thing: we pass the full fault-code to MmAccessFault and handle the rest from there in exactly the same way as before. More changes are coming to make things clear.
