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reworked COW join for Win8+

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This commit is contained in:
jonathan pickett
2014-08-12 12:20:35 -07:00
parent 6d364f41ce
commit 16cefcf0b5
2 changed files with 97 additions and 147 deletions
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src/Win32_Interop/Win32_FDAPI.h
+2
View File
@@ -265,5 +265,7 @@ int StorageSize(SOCKADDR_STORAGE *ss);
#endif
#ifdef __cplusplus
bool IsWindowsVersionAtLeast(WORD wMajorVersion, WORD wMinorVersion, WORD wServicePackMajor);
}
#endif
src/Win32_Interop/Win32_QFork.cpp
+95 -147
View File
@@ -20,7 +20,10 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "Win32_FDAPI.h"
#include <Windows.h>
#include <WinNT.h>
#include <errno.h>
#include <stdio.h>
#include <wchar.h>
@@ -45,8 +48,13 @@
#include <stdint.h>
#include <exception>
#include <algorithm>
#include <memory>
using namespace std;
#ifndef PAGE_REVERT_TO_FILE_MAP
#define PAGE_REVERT_TO_FILE_MAP 0x80000000 // From Win8.1 SDK
#endif
const long long cSentinelHeapSize = 30 * 1024 * 1024;
extern "C" int checkForSentinelMode(int argc, char **argv);
@@ -974,6 +982,84 @@ BOOL AbortForkOperation()
return FALSE;
}
void RejoinCOWPages(HANDLE mmHandle, byte* mmStart, size_t mmSize) {
SmartFileView<byte> copyView(
mmHandle,
FILE_MAP_WRITE,
0,
0,
mmSize,
string("RejoinCOWPages: Could not map COW back-copy view."));
HANDLE hProcess = GetCurrentProcess();
int pages = (int)(mmSize / pageSize);
shared_ptr<PSAPI_WORKING_SET_EX_INFORMATION> pwsi(
new PSAPI_WORKING_SET_EX_INFORMATION[pages],
[](PSAPI_WORKING_SET_EX_INFORMATION *p) { delete[] p; });
if (pwsi == NULL) {
throw new system_error(
GetLastError(),
system_category(),
"pwsi == NULL");
}
memset(pwsi.get(), 0, sizeof(PSAPI_WORKING_SET_EX_INFORMATION)* pages);
int virtualLockFailures = 0;
for (int page = 0; page < pages; page++) {
pwsi.get()[page].VirtualAddress = mmStart + page * pageSize;
}
if (QueryWorkingSetEx(
hProcess,
pwsi.get(),
sizeof(PSAPI_WORKING_SET_EX_INFORMATION)* pages) == FALSE) {
throw system_error(
GetLastError(),
system_category(),
"RejoinCOWPages: QueryWorkingSet failure");
}
for (int page = 0; page < pages; page++) {
if (pwsi.get()[page].VirtualAttributes.Valid == 1) {
// A 0 share count indicates a COW page
if (pwsi.get()[page].VirtualAttributes.ShareCount == 0) {
memcpy(copyView + (page*pageSize), mmStart + (page*pageSize), pageSize);
}
}
}
// If the COWs are not discarded, then there is no way of propagating changes into subsequent fork operations.
if (IsWindowsVersionAtLeast(8, 0, 0)) {
// restores all page protections on the view and culls the COW pages.
DWORD oldProtect;
if (FALSE == VirtualProtect(mmStart, pages * pageSize, PAGE_READWRITE | PAGE_REVERT_TO_FILE_MAP, &oldProtect)) {
throw std::system_error(GetLastError(), std::system_category(), "RejoinCOWPages: COW cull failed");
}
} else {
// Prior to Win8 unmapping the view was the only way to discard the COW pages from the view. Unfortunately this forces
// the view to be completely flushed to disk, which is a bit inefficient.
if (UnmapViewOfFile(mmStart) == FALSE) {
throw std::system_error(
GetLastError(),
system_category(),
"RejoinCOWPages: UnmapViewOfFile failed.");
}
// There is a race condition here. Something could map into the virtual address space used by the heap at the moment
// we are discarding local changes. There is nothing to do but report the problem and exit. This problem does not
// exist with the code above in Win8+ as the view is never unmapped.
LPVOID remapped =
MapViewOfFileEx(
mmHandle,
FILE_MAP_ALL_ACCESS,
0, 0,
0,
mmStart);
if (remapped == NULL) {
throw std::system_error(
GetLastError(),
system_category(),
"RejoinCOWPages: MapViewOfFileEx failed. Please upgrade your OS to Win8 or newer.");
}
}
}
BOOL EndForkOperation(int * pExitCode) {
try {
@@ -1028,154 +1114,16 @@ BOOL EndForkOperation(int * pExitCode) {
"EndForkOperation: ResetEvent() failed.");
}
// restore protection constants on shared memory blocks
DWORD oldProtect = 0;
if (VirtualProtect(g_pQForkControl, sizeof(QForkControl), PAGE_READWRITE, &oldProtect) == FALSE) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: VirtualProtect failed.");
}
if (VirtualProtect(
g_pQForkControl->heapStart,
g_pQForkControl->availableBlocksInHeap * g_pQForkControl->heapBlockSize,
PAGE_READWRITE,
&oldProtect) == FALSE ) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: VirtualProtect failed.");
}
// move local changes back into memory mapped views for next fork operation
RejoinCOWPages(
g_pQForkControl->heapMemoryMap,
(byte*)g_pQForkControl->heapStart,
g_pQForkControl->availableBlocksInHeap * cAllocationGranularity);
//
// What can be done to unify COW pages back into the section?
//
// 1. find the modified pages
// 2. copy the modified pages into a buffer
// 3. close the section map (discarding local changes)
// 4. reopen the section map
// 5. copy modified pages over reopened section map
//
// This assumes that the forked process is reasonably quick, such that this copy is not a huge burden.
//
typedef vector<INT_PTR> COWList;
typedef COWList::iterator COWListIterator;
COWList cowList;
HANDLE hProcess = GetCurrentProcess();
size_t mmSize = g_pQForkControl->availableBlocksInHeap * g_pQForkControl->heapBlockSize;
int pages = (int)(mmSize / pageSize);
PSAPI_WORKING_SET_EX_INFORMATION* pwsi =
new PSAPI_WORKING_SET_EX_INFORMATION[pages];
if (pwsi == NULL) {
throw new system_error(
GetLastError(),
system_category(),
"pwsi == NULL");
}
memset(pwsi, 0, sizeof(PSAPI_WORKING_SET_EX_INFORMATION) * pages);
int virtualLockFailures = 0;
for (int page = 0; page < pages; page++) {
pwsi[page].VirtualAddress = (BYTE*)g_pQForkControl->heapStart + page * pageSize;
}
if (QueryWorkingSetEx(
hProcess,
pwsi,
sizeof(PSAPI_WORKING_SET_EX_INFORMATION) * pages) == FALSE) {
throw system_error(
GetLastError(),
system_category(),
"QueryWorkingSet failure");
}
for (int page = 0; page < pages; page++) {
if (pwsi[page].VirtualAttributes.Valid == 1) {
// A 0 share count indicates a COW page
if (pwsi[page].VirtualAttributes.ShareCount == 0) {
cowList.push_back(page);
}
}
}
if (cowList.size() > 0) {
LPBYTE cowBuffer = (LPBYTE)malloc(cowList.size() * pageSize);
int bufPageIndex = 0;
for (COWListIterator cli = cowList.begin(); cli != cowList.end(); cli++) {
memcpy(
cowBuffer + (bufPageIndex * pageSize),
(BYTE*)g_pQForkControl->heapStart + ((*cli) * pageSize),
pageSize);
bufPageIndex++;
}
delete [] pwsi;
pwsi = NULL;
// discard local changes
if (UnmapViewOfFile(g_pQForkControl->heapStart) == FALSE) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: UnmapViewOfFile failed.");
}
g_pQForkControl->heapStart =
MapViewOfFileEx(
g_pQForkControl->heapMemoryMap,
FILE_MAP_ALL_ACCESS,
0,0,
0,
g_pQForkControl->heapStart);
if (g_pQForkControl->heapStart == NULL) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: Remapping ForkControl block failed.");
}
// copied back local changes to remapped view
bufPageIndex = 0;
for (COWListIterator cli = cowList.begin(); cli != cowList.end(); cli++) {
memcpy(
(BYTE*)g_pQForkControl->heapStart + ((*cli) * pageSize),
cowBuffer + (bufPageIndex * pageSize),
pageSize);
bufPageIndex++;
}
delete cowBuffer;
cowBuffer = NULL;
}
// now do the same with qfork control
LPVOID controlCopy = malloc(sizeof(QForkControl));
if(controlCopy == NULL) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: allocation failed.");
}
memcpy(controlCopy, g_pQForkControl, sizeof(QForkControl));
if (UnmapViewOfFile(g_pQForkControl) == FALSE) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: UnmapViewOfFile failed.");
}
g_pQForkControl = (QForkControl*)
MapViewOfFileEx(
g_hQForkControlFileMap,
FILE_MAP_ALL_ACCESS,
0,0,
0,
g_pQForkControl);
if (g_pQForkControl == NULL) {
throw std::system_error(
GetLastError(),
system_category(),
"EndForkOperation: Remapping ForkControl failed.");
}
memcpy(g_pQForkControl, controlCopy,sizeof(QForkControl));
delete controlCopy;
controlCopy = NULL;
RejoinCOWPages(
g_hQForkControlFileMap,
(byte*)g_pQForkControl,
sizeof(QForkControl));
return TRUE;
}