It is reported that there is a performance issue in the ACPICA OSL
implementation around memory mappings.
On the reported platforms, there is a debugging facility implemented in the
ACPI namespace using circular logging buffer:
Name (DPTR, 0x3AFEB000)
Name (EPTR, 0x3AFFB000)
Name (CPTR, 0x3AFEB010)
Mutex (MMUT, 0x00)
Method (MDBG, 1, Serialized)
{
Store (Acquire (MMUT, 0x03E8), Local0)
If (Local0 == Zero)
{
OperationRegion (ABLK, SystemMemory, CPTR, 0x10)
Field (ABLK, ByteAcc, NoLock, Preserve)
{
AAAA, 128
}
Store (Arg0, AAAA) /* \MDBG.AAAA */
CPTR = (CPTR + 0x10) /* \CPTR */
If (CPTR >= EPTR)
{
CPTR = (DPTR + 0x10) /* \CPTR */
}
Release (MMUT)
}
Return (Local0)
}
This function is heavily invoked by other ACPI control methods.
The reported platforms suffer from 2-5 minutes kernel stuck in the end of
accessing the mapped circular buffer system memory region. By
instrumentation, the 2-5 minutes time consumption overhead can be seen to
happen on the synchronize_rcu() invoked in the acpi_os_unmap_memory().
This patchset removes the synchronize_rcu() from the hot path to improve
the performance.
Lv Zheng (6):
ACPI/OSL: Split memory operation region implementations to a seperate
file.
ACPI/OSL: Rename system memory functions.
ACPI/OSL: Cleanup memory access functions by merging duplicate code.
ACPI/OSL: Add acpi_map2virt() to merge duplicate code.
ACPI/OSL: Cleanup branch logics.
ACPI/OSL: Fix performance issue in system memory lockings.
drivers/acpi/Makefile | 2 +-
drivers/acpi/mem.c | 414 +++++++++++++++++++++++++++++++++++++++++++++++++
drivers/acpi/osl.c | 381 ---------------------------------------------
3 files changed, 415 insertions(+), 382 deletions(-)
create mode 100644 drivers/acpi/mem.c
--
1.7.10
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