When we're about to close a file (ie, forget everything about it
and release any associated structure), actually delay it.
This allows keep data fresh in memory for faster reuse in case
it would be required. The effective closing will only happen after some time.
For specific operations, this will produce a real speed up in ReactOS.
For instance, with that patch, Winamp starts within seconds, instead of dozen
of minutes.
In most cases, it will bring ReactOS to performances it had before fixing
the huge leak in FastFAT (commit 94ead99) without leaking the whole FS.
For now, due to regressions, this is only activated for files and not
for directories. Once it gets fixed, it will be enabled for both.
CORE-14826
CORE-14917
This avoids initializing cache directly on directory
open/create.
The advantage is we reduce the load on cache manager
and on memory manager by avoiding creating everytime
a stream file object, and initializing cache for it.
This will avoid initializing cache for started
applications 'current directory' which is just opened
for having a valid handle but no read/write is performed
in it, by default.
This is a step forward for autochk.
CORE-14629
This is a PoC of what it's possible to realize thanks to an
already existing hack in ntoskrnl :-).
With this extension, on the kdb:> prompt, you're able to type
in commands that will be handled by the FastFAT driver and not
by the kernel, allowing internal debug, not possible otherwise.
So far, three commands exist:
- ?fat.vols: lists all the mounted volumes by FastFAT
- ?fat.files: lists all the files on a specific volume (with their attributes)
- ?fat.setdbgfile: allows watching on specifics files lifetime
This is obviously only the begin and could be greatly improved.
For instance, this is what allowed to debug CORE-14557
Once a directory is crossed (opened or a child is opened), associated
FCB structure is created in FastFAT, but also a stream FO for caching.
Up to now, due to an extra reference taken by the stream file object,
even when the directory was no longer used, the directory was kept in
memory: the FCB was never deleted, the file object was never dereferenced,
and the cache never released.
The immediate effect of this bug is that our FAT driver was leaking every
directory that was used affecting the whole OS situation. In case of
directories intensive operation (like extraction the ReactOS source code
in ReactOS ;-)), we were just killin the whole OS RAM without any way to
release it and recover.
The other side effects: IOs were faster as half of the FS was always
permanant in RAM.
This commit fixes the issue by forcing the FSD to release the FO,
and the cache when a directory is no longer used, leading to its
destruction in RAM.
Downside: on IO intensive operation, expect slowdowns, obviously,
there's less caching now. But more efficient!
CORE-14557
