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dll: dirbuf:

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- FspFileSystemAcquireDirectoryBufferEx takes hint for initial capacity.
- Buffer allocation strategy has been improved to minimize reallocation.
- Quick sort of directory entries now implements median of three partitioning. This improves performance of sorting already sorted data.
This commit is contained in:
Bill Zissimopoulos
2022-03-22 16:47:40 +00:00
parent 868812d248
commit 7527155cb8
4 changed files with 102 additions and 20 deletions
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18
tst/ntptfs/ptfs.c
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@ -24,12 +24,14 @@
#define FileSystemContext ((PTFS *)(FileSystem)->UserContext)
#define FileContextHandle (((FILE_CONTEXT *)(FileContext))->Handle)
#define FileContextIsDirectory (((FILE_CONTEXT *)(FileContext))->IsDirectory)
#define FileContextDirFileSize (((FILE_CONTEXT *)(FileContext))->DirFileSize)
#define FileContextDirBuffer (&((FILE_CONTEXT *)(FileContext))->DirBuffer)
typedef struct
{
HANDLE Handle;
BOOLEAN IsDirectory;
ULONG DirFileSize;
PVOID DirBuffer;
} FILE_CONTEXT;
@ -241,6 +243,7 @@ static NTSTATUS CreateEx(FSP_FILE_SYSTEM *FileSystem,
memset(FileContext, 0, sizeof *FileContext);
FileContext->Handle = Handle;
FileContext->IsDirectory = IsDirectory;
FileContext->DirFileSize = (ULONG)FileInfo->FileSize;
*PFileContext = FileContext;
Result = STATUS_SUCCESS;
@ -331,6 +334,7 @@ static NTSTATUS Open(FSP_FILE_SYSTEM *FileSystem,
memset(FileContext, 0, sizeof *FileContext);
FileContext->Handle = Handle;
FileContext->IsDirectory = IsDirectory;
FileContext->DirFileSize = (ULONG)FileInfo->FileSize;
*PFileContext = FileContext;
Result = STATUS_SUCCESS;
@ -787,6 +791,18 @@ static NTSTATUS BufferedReadDirectory(FSP_FILE_SYSTEM *FileSystem,
{
PTFS *Ptfs = FileSystemContext;
HANDLE Handle = FileContextHandle;
ULONG CapacityHint = FileContextDirFileSize;
/*
* An analysis of the relationship between the required buffer capacity and the
* NTFS directory size (as reported by FileStandardInformation) showed the ratio
* between the two to be between 0.5 and 1 with some outliers outside those bounds.
* (For this analysis file names of average length of 4 or 24 were used and NTFS
* had 8.3 file names disabled.)
*
* We use the NTFS directory size as our capacity hint (i.e. ratio of 1), which
* means that we may overestimate the required buffer capacity in most cases.
* This is ok since our goal is to improve performance.
*/
PVOID PDirBuffer = FileContextDirBuffer;
BOOLEAN RestartScan;
ULONG BytesTransferred;
@ -801,7 +817,7 @@ static NTSTATUS BufferedReadDirectory(FSP_FILE_SYSTEM *FileSystem,
NTSTATUS Result, DirBufferResult;
DirBufferResult = STATUS_SUCCESS;
if (FspFileSystemAcquireDirectoryBuffer(PDirBuffer, 0 == Marker, &DirBufferResult))
if (FspFileSystemAcquireDirectoryBufferEx(PDirBuffer, 0 == Marker, CapacityHint, &DirBufferResult))
{
for (RestartScan = TRUE;; RestartScan = FALSE)
{