[ros-arm-bringup] 32358: Why divide up the page array into chunks of 128 pages? Why have a nested loop to initialize system memory in chunks of 128 pages? Why zero the array entries in chunks of 128? The page array is now initialized by simply iterating every page on the system, and filling out its entry in the array. Moved out the division calculations even one more step out of the loop -- now they're really calculated once, instead of 1000 times (an improvement over the 400000 times they were

Author: ros-arm-bringup
Date: Thu Feb 14 19:59:14 2008
New Revision: 32358

URL: http://svn.reactos.org/svn/reactos?rev=32358&view=rev
Log:
Why divide up the page array into chunks of 128 pages? Why have a nested loop to
initialize system memory in chunks of 128 pages? Why zero the array entries in chunks of
128? The page array is now initialized by simply iterating every page on the system, and
filling out its entry in the array.
Moved out the division calculations even one more step out of the loop -- now they're
really calculated once, instead of 1000 times (an improvement over the 400000 times they
were calculated previously).

Modified:
    trunk/reactos/ntoskrnl/mm/freelist.c

Modified: trunk/reactos/ntoskrnl/mm/freelist.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/freelist.c?rev…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/freelist.c (original)
+++ trunk/reactos/ntoskrnl/mm/freelist.c Thu Feb 14 19:59:14 2008
@@ -292,7 +292,10 @@
     NTSTATUS Status;
     PFN_TYPE LastPage, Pfn;
     ULONG PdeStart = PsGetCurrentProcess()->Pcb.DirectoryTableBase.LowPart;
-    
+    ULONG PdePageStart, PdePageEnd;
+    ULONG VideoPageStart, VideoPageEnd;
+    ULONG KernelPageStart, KernelPageEnd;
+
     /* Initialize the page lists */
     KeInitializeSpinLock(&PageListLock);
     InitializeListHead(&UserPageListHead);
@@ -341,133 +344,119 @@
         }
     }
     
-    /* Now loop every PFN database page again */
-    for (i = 0; i < Reserved; i++)
-    {
-        PVOID Address = (char*)MmPageArray + (i * PAGE_SIZE);
-        ULONG j, start, end;
-        ULONG PdePageStart, PdePageEnd;
-        ULONG VideoPageStart, VideoPageEnd;
-        ULONG KernelPageStart, KernelPageEnd;
-        
-        /* Clear the page array entry */
-        memset(Address, 0, PAGE_SIZE);
-        
-        /* Do the next page'ss worth of entries */
-        start = ((ULONG_PTR)Address - (ULONG_PTR)MmPageArray) / sizeof(PHYSICAL_PAGE);
-        end = ((ULONG_PTR)Address - (ULONG_PTR)MmPageArray + PAGE_SIZE) /
sizeof(PHYSICAL_PAGE);
-        
-        /* We'll be applying a bunch of hacks -- precompute some static values */
-        PdePageStart = PdeStart / PAGE_SIZE;
-        PdePageEnd = MmFreeLdrPageDirectoryEnd / PAGE_SIZE;
-        VideoPageStart = 0xA0000 / PAGE_SIZE;
-        VideoPageEnd = 0x100000 / PAGE_SIZE;
-        KernelPageStart = FirstPhysKernelAddress / PAGE_SIZE;
-        KernelPageEnd = LastPhysKernelAddress / PAGE_SIZE;
-        
-        /* Loop each page in this chunk */
-        for (j = start; j < end; j++)
+    /* Clear the PFN database */
+    RtlZeroMemory(MmPageArray, MmPageArraySize * sizeof(PHYSICAL_PAGE));
+    
+    /* We'll be applying a bunch of hacks -- precompute some static values */
+    PdePageStart = PdeStart / PAGE_SIZE;
+    PdePageEnd = MmFreeLdrPageDirectoryEnd / PAGE_SIZE;
+    VideoPageStart = 0xA0000 / PAGE_SIZE;
+    VideoPageEnd = 0x100000 / PAGE_SIZE;
+    KernelPageStart = FirstPhysKernelAddress / PAGE_SIZE;
+    KernelPageEnd = LastPhysKernelAddress / PAGE_SIZE;
+    
+    /* Loop every page on the system */
+    for (i = 0; i < MmPageArraySize; i++)
+    {                
+        /* Check if it's part of RAM */
+        if (MiIsPfnRam(BIOSMemoryMap, AddressRangeCount, i))
         {
-            /* Check if it's part of RAM */
-            if (MiIsPfnRam(BIOSMemoryMap, AddressRangeCount, j))
-            {
-                /* Apply assumptions that all computers are built the same way */
-                if (j == 0)
-                {
-                    /* Page 0 is reserved for the IVT */
-                    MmPageArray[0].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                    MmPageArray[0].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[0].Flags.Zero = 0;
-                    MmPageArray[0].ReferenceCount = 0;
-                    MmStats.NrReservedPages++;
-                }
-                else if (j == 1)
-                {
-                    /* Page 1 is reserved for the PCR */
-                    MmPageArray[1].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                    MmPageArray[1].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[1].Flags.Zero = 0;
-                    MmPageArray[1].ReferenceCount = 1;
-                    MmStats.NrReservedPages++;
-                }
-                else if (j == 2)
-                {
-                    /* Page 2 is reserved for the KUSER_SHARED_DATA */
-                    MmPageArray[2].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                    MmPageArray[2].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[2].Flags.Zero = 0;
-                    MmPageArray[2].ReferenceCount = 1;
-                    MmStats.NrReservedPages++;
-                }
-                else if ((j >= PdePageStart) && (j < PdePageEnd))
-                {
-                    /* These pages contain the initial FreeLDR PDEs */
-                    MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                    MmPageArray[j].Flags.Zero = 0;
-                    MmPageArray[j].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[j].ReferenceCount = 1;
-                    MmStats.NrReservedPages++;
-                }
-                else if ((j >= VideoPageStart) && (j < VideoPageEnd))
-                {
-                    /*
-                     * These pages are usually for the Video ROM BIOS.
-                     * Supposedly anyway. We'll simply ignore the fact that
-                     * many systems have this area somewhere else entirely
-                     * (which we'll assume to be "free" a couple of lines
below)
-                     */
-                    MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                    MmPageArray[j].Flags.Zero = 0;
-                    MmPageArray[j].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[j].ReferenceCount = 1;
-                    MmStats.NrReservedPages++;
-                }
-                else if ((j >= KernelPageStart) && (j < KernelPageEnd))
-                {
-                    /* These are pages beloning to the kernel */
-                    MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_USED;
-                    MmPageArray[j].Flags.Zero = 0;
-                    MmPageArray[j].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[j].ReferenceCount = 2;
-                    MmPageArray[j].MapCount = 1;
-                    MmStats.NrSystemPages++;
-                }
-                else if (j > LastPage)
-                {
-                    /* These are pages we allocated above to hold the PFN DB */
-                    MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_USED;
-                    MmPageArray[j].Flags.Zero = 0;
-                    MmPageArray[j].Flags.Consumer = MC_NPPOOL;
-                    MmPageArray[j].ReferenceCount = 2;
-                    MmPageArray[j].MapCount = 1;
-                    MmStats.NrSystemPages++;
-                }
-                else
-                {
-                    /*
-                     * These are supposedly free pages.
-                     * By the way, not all of them are, some contain vital
-                     * FreeLDR data, but since we choose to ignore the Memory
-                     * Descriptor List, why bother, right?
-                     */
-                    MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_FREE;
-                    MmPageArray[j].Flags.Zero = 0;
-                    MmPageArray[j].ReferenceCount = 0;
-                    InsertTailList(&FreeUnzeroedPageListHead,
-                                   &MmPageArray[j].ListEntry);
-                    UnzeroedPageCount++;
-                    MmStats.NrFreePages++;
-                }
+            /* Apply assumptions that all computers are built the same way */
+            if (i == 0)
+            {
+                /* Page 0 is reserved for the IVT */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].ReferenceCount = 0;
+                MmStats.NrReservedPages++;
+            }
+            else if (i == 1)
+            {
+                /* Page 1 is reserved for the PCR */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].ReferenceCount = 1;
+                MmStats.NrReservedPages++;
+            }
+            else if (i == 2)
+            {
+                /* Page 2 is reserved for the KUSER_SHARED_DATA */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].ReferenceCount = 1;
+                MmStats.NrReservedPages++;
+            }
+            else if ((i >= PdePageStart) && (i < PdePageEnd))
+            {
+                /* These pages contain the initial FreeLDR PDEs */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].ReferenceCount = 1;
+                MmStats.NrReservedPages++;
+            }
+            else if ((i >= VideoPageStart) && (i < VideoPageEnd))
+            {
+                /*
+                 * These pages are usually for the Video ROM BIOS.
+                 * Supposedly anyway. We'll simply ignore the fact that
+                 * many systems have this area somewhere else entirely
+                 * (which we'll assume to be "free" a couple of lines
below)
+                 */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].ReferenceCount = 1;
+                MmStats.NrReservedPages++;
+            }
+            else if ((i >= KernelPageStart) && (i < KernelPageEnd))
+            {
+                /* These are pages beloning to the kernel */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_USED;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].ReferenceCount = 2;
+                MmPageArray[i].MapCount = 1;
+                MmStats.NrSystemPages++;
+            }
+            else if (i > LastPage)
+            {
+                /* These are pages we allocated above to hold the PFN DB */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_USED;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+                MmPageArray[i].ReferenceCount = 2;
+                MmPageArray[i].MapCount = 1;
+                MmStats.NrSystemPages++;
             }
             else
             {
-                /* These are pages reserved by the BIOS/ROMs */
-                MmPageArray[j].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
-                MmPageArray[j].Flags.Consumer = MC_NPPOOL;
-                MmPageArray[j].Flags.Zero = 0;
-                MmPageArray[j].ReferenceCount = 0;
-                MmStats.NrReservedPages++;
-            }
+                /*
+                 * These are supposedly free pages.
+                 * By the way, not all of them are, some contain vital
+                 * FreeLDR data, but since we choose to ignore the Memory
+                 * Descriptor List, why bother, right?
+                 */
+                MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_FREE;
+                MmPageArray[i].Flags.Zero = 0;
+                MmPageArray[i].ReferenceCount = 0;
+                InsertTailList(&FreeUnzeroedPageListHead,
+                               &MmPageArray[i].ListEntry);
+                UnzeroedPageCount++;
+                MmStats.NrFreePages++;
+            }
+        }
+        else
+        {
+            /* These are pages reserved by the BIOS/ROMs */
+            MmPageArray[i].Flags.Type = MM_PHYSICAL_PAGE_BIOS;
+            MmPageArray[i].Flags.Consumer = MC_NPPOOL;
+            MmPageArray[i].Flags.Zero = 0;
+            MmPageArray[i].ReferenceCount = 0;
+            MmStats.NrReservedPages++;
         }
     }