Source code of Windows XP (NT5)
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To-Do List for LKRhash
======================
TESTING
=======
* Write a C test, to directly test the C API. HashTest half does
it, as it can use the public API and TypedHashTable.
* Build a publicly distributable test program, as a sample for
customers. E.g., a dictionary component for ASP.
* hashtest: modify so that each thread can work on a completely
separate hashtable, instead of sharing a global
hashtable. This will allow us to discover the maximum possible
scaling, which is probably less than the `ideal' scaling,
#CPUs * 1-thread-perf.
* hashtest\kernel: split into driver and usermode test
program. Usermode test program should take care of parsing the
arguments and loading the test data into memory, then use an
ioctl to pass it down to the kernel driver. The only code in
the kernel driver,apart from LKRhash itself, should be the goo
to crack the ioctl and DriverEntry. Usermode should print
results.
* Better tests for ApplyIf family
KERNEL-MODE
===========
* kernel locks: should they block at all? consider implications
if running on some usermode program's thread.
* Fix global objects in driver, including the global list of
tables
* implement kernel-mode version of !lkrhash
* Think about running at DISPATCH_LEVEL instead of
PASSIVE_LEVEL. Which functions should be pageable
vs. non-pageable? Memory allocators? Lock types?
* Use <zwapi.h>?
* Memory allocation pool is a parameter for LKRhash
public constructors, but it's ignored. Need virtual base for
allocators?
* DONE: Control debug spew: provide some way of setting
g_fDebugOutputEnabled
LOCK IMPLEMENTATION
===================
* WriteLock: make all return a value instead of `void' that's
passed into WriteUnlock. Ditto for ReadLock, etc. Needed for
CKSpinLock and OldIrql. <sigh/>
* Put delays into the inner loop of the spins, to see if that
reduces cache sloshing
* Enable per-class instrumentation for locks, as opposed to the
current all-or-nothing system for per-lock
instrumentation. Mostly present already, just needs a little
factoring.
* Locks code. Move all member function implementations and enums
into locks.cpp. Locks.h should be opaque declarations only.
* Rewrite a few key functions, such as CSmallSpinLock::WriteLock
or CReaderWriterLock3::ReadOrWriteLock, in x86 assembler
* Build locks as a separate statically linked library
* Refcount the initialization/cleanup routines?
* Move CKSpinLock, CEResource, and CFastMutex into <Locks.h>
* DONE: Sprinkle KeEnterCriticalRegion (and KeLeaveCriticalRegion)
in the various locks, to prevent APCs being delivered that might
suspend the thread that holds the lock.
MISCELLANEOUS
=============
* Reduce the three versions of LKRhash in IIS6 to just this one.
* Currently, we key the number of subtables off LK_TABLESIZE
times a function of the number of CPUs. However, we only need
a lot of subtables under two circumstances: (a) many millions
of elements (esp. on Win64, where total number of elements
might exceed 2^32), or (b) high contention. There isn't
necessarily a correlation between large table size and high
contention. With the multi-reader locks, high contention only
arises if there are a lot of insertions/deletions. If the
table is not modified much after it's built, contention
shouldn't be an issue and there's little advantage to having a
lot of subtables.
* Provide a DeleteKey variant that returns a pointer to the
record that is being removed from the table.
* Make AddRefRecord return the new reference count.
* Inline the array of pointers to subtables within
CLKRHashTable, instead of dynamically allocating it.
* Inline _FindBucket by hand into Delete(Key|Record),
InsertRecord, and Find(Key|Record).
* Factor out memory stuff into LKR-mem.cpp
* Add some instrumentation: #allocs, #expands, #contracts, etc.
* Add some flags to LKR_Initialize: default size, output
tracing, etc
* Should ApplyIf(LKP_DELETE) call the Action function before
deleting? Or add LKP_PERFORM_DELETE[_STOP]
* Add debug print routines for the other enumerations and for
lock state to LKRhash.
* Experiment with having no bucket locks whatsoever, just
subtable locks. This should make operations a little faster,
but presumably will hurt multiprocessor scalability
* Implement fMultiKeys to provide support for multiple,
identical keys. Needed for EqualRange, hash_multiset, and
hash_multimap. See CLKRLinearHashTable::_InsertRecord for
details on what needs to be changed.
* Provide implementations of the STL collection classes:
hash_map, hash_set, hash_multimap, and hash_multiset. Must
provide full implementation of STL iterator semantics
(pair<key,value>)
* const_iterators for STL-style iterators
* consider providing some kind of implicit locking with
STL-style iterators
* Add version.subversion number to CLKRLinearHashTable
* Build lkrhash as a separate statically linked library
* Better Statistics: #buckets, density, by subtable
* Experiment with new hash function from Paul Larson.
* Public API in LKR-hash.h: remove dependency on irtlmisc.h and
irtldbg.h
* Use IsBadCodePtr to validate callback functions
* Make exception-safe. What happens if callback routines
(AddRefRecord/ExtractKeys or ApplyIf) access violate (throw an
SEH exception) or throw a C++ exception? Table and bucket
locks won't be released, state variables may be corrupted,
etc. LKRhash code should never throw any kind of exception
* Add some kind of auto object for readlocking or writelocking a
table, so that the table automatically gets unlocked by
auto-obj's destructor.
* Use auto_ptrs.
* Port to C# (Chris Tracy has started on this).
Andre Rosenthal has started a port to Managed C++
* Make LKRhash available as a static library as well as a DLL
* DONE: break apart lkrhash.cpp: iterators, applyif, stats, etc
* DONE: Always step forward through all subtables, to avoid
possible deadlock, when acquiring subtable locks
* DONE: Test new contraction algorithm.
* DONE: sublocks for ApplyIf
* DONE: Provide a C API wrapper