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[NTOKSRNL] Don't blindly schedule read-ahead on CcCopyRead() call.

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This avoids locking Cc for too long by trying to read-ahead data which
is already in cache.
We now will only schedule a read ahead if next read should bring us
to a new VACB (perhaps not in cache).

This notably fixes Inkscape setup which was slown down by read-ahead
due to continous 1 byte reads.

Thanks to Thomas for his help on this issue.

CORE-14395
This commit is contained in:
Pierre Schweitzer 2018-02-28 20:54:53 +01:00
parent 2baafa61c6
commit c4f58bbfd8
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GPG key ID: 7545556C3D585B0B
1 changed files with 5 additions and 2 deletions
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7
ntoskrnl/cc/copy.c
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@ -377,8 +377,11 @@ CcCopyData (
/* If that was a successful sync read operation, let's handle read ahead */ /* If that was a successful sync read operation, let's handle read ahead */
if (Operation == CcOperationRead && Length == 0 && Wait) if (Operation == CcOperationRead && Length == 0 && Wait)
{ {
/* If file isn't random access, schedule next read */ /* If file isn't random access and next read may get us cross VACB boundary,
if (!BooleanFlagOn(FileObject->Flags, FO_RANDOM_ACCESS)) * schedule next read
*/
if (!BooleanFlagOn(FileObject->Flags, FO_RANDOM_ACCESS) &&
(CurrentOffset - 1) / VACB_MAPPING_GRANULARITY != (CurrentOffset + BytesCopied - 1) / VACB_MAPPING_GRANULARITY)
{ {
CcScheduleReadAhead(FileObject, (PLARGE_INTEGER)&FileOffset, BytesCopied); CcScheduleReadAhead(FileObject, (PLARGE_INTEGER)&FileOffset, BytesCopied);
} }