From: "Rafael J. Wysocki" <rafael@kernel.org>
To: "Kaneda, Erik" <erik.kaneda@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
Len Brown <lenb@kernel.org>, Borislav Petkov <bp@alien8.de>,
"Weiny, Ira" <ira.weiny@intel.com>,
James Morse <james.morse@arm.com>,
Myron Stowe <myron.stowe@redhat.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"Moore, Robert" <robert.moore@intel.com>
Subject: Re: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on interpreter exit
Date: Fri, 12 Jun 2020 14:05:01 +0200 [thread overview]
Message-ID: <CAJZ5v0h0ax4N-Tk+MfAeAyJ_tDYPW5vseqUU49UShBKZ4+F6Bw@mail.gmail.com> (raw)
In-Reply-To: <BYAPR11MB30963CB784B940A5CD58C4FAF0810@BYAPR11MB3096.namprd11.prod.outlook.com>
On Fri, Jun 12, 2020 at 2:12 AM Kaneda, Erik <erik.kaneda@intel.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Rafael J. Wysocki <rjw@rjwysocki.net>
> > Sent: Wednesday, June 10, 2020 5:22 AM
> > To: Williams, Dan J <dan.j.williams@intel.com>
> > Cc: Kaneda, Erik <erik.kaneda@intel.com>; Wysocki, Rafael J
> > <rafael.j.wysocki@intel.com>; Len Brown <lenb@kernel.org>; Borislav
> > Petkov <bp@alien8.de>; Weiny, Ira <ira.weiny@intel.com>; James Morse
> > <james.morse@arm.com>; Myron Stowe <myron.stowe@redhat.com>;
> > Andy Shevchenko <andriy.shevchenko@linux.intel.com>; linux-
> > kernel@vger.kernel.org; linux-acpi@vger.kernel.org; linux-
> > nvdimm@lists.01.org; Moore, Robert <robert.moore@intel.com>
> > Subject: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on
> > interpreter exit
> >
> > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> >
> > For transient memory opregions that are created dynamically under
> > the namespace and interpreter mutexes and go away quickly, there
> > still is the problem that removing their memory mappings may take
> > significant time and so doing that while holding the mutexes should
> > be avoided.
> >
> > For example, unmapping a chunk of memory associated with a memory
> > opregion in Linux involves running synchronize_rcu_expedited()
> > which really should not be done with the namespace mutex held.
> >
> > To address that problem, notice that the unused memory mappings left
> > behind by the "dynamic" opregions that went away need not be unmapped
> > right away when the opregion is deactivated. Instead, they may be
> > unmapped when exiting the interpreter, after the namespace and
> > interpreter mutexes have been dropped (there's one more place dealing
> > with opregions in the debug code that can be treated analogously).
> >
> > Accordingly, change acpi_ev_system_memory_region_setup() to put
> > the unused mappings into a global list instead of unmapping them
> > right away and add acpi_ev_system_release_memory_mappings() to
> > be called when leaving the interpreter in order to unmap the
> > unused memory mappings in the global list (which is protected
> > by the namespace mutex).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> > drivers/acpi/acpica/acevents.h | 2 ++
> > drivers/acpi/acpica/dbtest.c | 3 ++
> > drivers/acpi/acpica/evrgnini.c | 51
> > ++++++++++++++++++++++++++++++++--
> > drivers/acpi/acpica/exutils.c | 3 ++
> > drivers/acpi/acpica/utxface.c | 23 +++++++++++++++
> > include/acpi/acpixf.h | 1 +
> > 6 files changed, 80 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/acpi/acpica/acevents.h b/drivers/acpi/acpica/acevents.h
> > index 79f292687bd6..463eb9124765 100644
> > --- a/drivers/acpi/acpica/acevents.h
> > +++ b/drivers/acpi/acpica/acevents.h
> > @@ -197,6 +197,8 @@ acpi_ev_execute_reg_method(union
> > acpi_operand_object *region_obj, u32 function);
> > /*
> > * evregini - Region initialization and setup
> > */
> > +void acpi_ev_system_release_memory_mappings(void);
> > +
> > acpi_status
> > acpi_ev_system_memory_region_setup(acpi_handle handle,
> > u32 function,
> > diff --git a/drivers/acpi/acpica/dbtest.c b/drivers/acpi/acpica/dbtest.c
> > index 6db44a5ac786..7dac6dae5c48 100644
> > --- a/drivers/acpi/acpica/dbtest.c
> > +++ b/drivers/acpi/acpica/dbtest.c
> > @@ -8,6 +8,7 @@
> > #include <acpi/acpi.h>
> > #include "accommon.h"
> > #include "acdebug.h"
> > +#include "acevents.h"
> > #include "acnamesp.h"
> > #include "acpredef.h"
> > #include "acinterp.h"
> > @@ -768,6 +769,8 @@ acpi_db_test_field_unit_type(union
> > acpi_operand_object *obj_desc)
> > acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
> > acpi_ut_release_mutex(ACPI_MTX_INTERPRETER);
> >
> > + acpi_ev_system_release_memory_mappings();
> > +
> > bit_length = obj_desc->common_field.bit_length;
> > byte_length =
> > ACPI_ROUND_BITS_UP_TO_BYTES(bit_length);
> >
> > diff --git a/drivers/acpi/acpica/evrgnini.c b/drivers/acpi/acpica/evrgnini.c
> > index 48a5e6eaf9b9..946c4eef054d 100644
> > --- a/drivers/acpi/acpica/evrgnini.c
> > +++ b/drivers/acpi/acpica/evrgnini.c
> > @@ -16,6 +16,52 @@
> > #define _COMPONENT ACPI_EVENTS
> > ACPI_MODULE_NAME("evrgnini")
> >
> > +#ifdef ACPI_OS_MAP_MEMORY_FAST_PATH
> > +static struct acpi_mem_mapping *unused_memory_mappings;
> > +
> > +/*********************************************************
> > **********************
> > + *
> > + * FUNCTION: acpi_ev_system_release_memory_mappings
> > + *
> > + * PARAMETERS: None
> > + *
> > + * RETURN: None
> > + *
> > + * DESCRIPTION: Release all of the unused memory mappings in the queue
> > + * under the interpreter mutex.
> > + *
> > +
> > **********************************************************
> > ********************/
> > +void acpi_ev_system_release_memory_mappings(void)
> > +{
> > + struct acpi_mem_mapping *mapping;
> > +
> > +
> > ACPI_FUNCTION_TRACE(acpi_ev_system_release_memory_mappin
> > gs);
> > +
> > + acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
> > +
> > + while (unused_memory_mappings) {
> > + mapping = unused_memory_mappings;
> > + unused_memory_mappings = mapping->next;
> > +
> > + acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
> > +
> > + acpi_os_unmap_memory(mapping->logical_address,
> > mapping->length);
>
> acpi_os_unmap_memory calls synchronize_rcu_expedited(). I'm no RCU expert but the
> definition of this function states:
>
> * Although this is a great improvement over previous expedited
> * implementations, it is still unfriendly to real-time workloads, so is
> * thus not recommended for any sort of common-case code. In fact, if
> * you are using synchronize_rcu_expedited() in a loop, please restructure
> * your code to batch your updates, and then use a single synchronize_rcu()
> * instead.
If this really ends up being a loop, the code without this patch will
also call synchronize_rcu_expedited() in a loop, but indirectly and
under the namespace and interpreter mutexes.
While I agree that this is still somewhat suboptimal, improving this
would require more changes in the OSL code.
Cheers!
next prev parent reply other threads:[~2020-06-12 12:05 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 23:39 [PATCH v2] ACPI: Drop rcu usage for MMIO mappings Dan Williams
2020-06-05 13:32 ` Rafael J. Wysocki
2020-06-05 16:18 ` Dan Williams
2020-06-05 16:21 ` Rafael J. Wysocki
2020-06-05 16:39 ` Dan Williams
2020-06-05 17:02 ` Rafael J. Wysocki
2020-06-05 14:06 ` [RFT][PATCH] ACPI: OSL: Use rwlock instead of RCU for memory management Rafael J. Wysocki
2020-06-05 17:08 ` Dan Williams
2020-06-06 6:56 ` Rafael J. Wysocki
2020-06-08 15:33 ` Rafael J. Wysocki
2020-06-08 16:29 ` Rafael J. Wysocki
2020-06-05 19:40 ` Andy Shevchenko
2020-06-06 6:48 ` Rafael J. Wysocki
2020-06-10 12:17 ` [RFT][PATCH 0/3] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki
2020-06-10 12:20 ` [RFT][PATCH 1/3] ACPICA: Defer unmapping of memory used in memory opregions Rafael J. Wysocki
2020-06-10 12:21 ` [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on interpreter exit Rafael J. Wysocki
2020-06-12 0:12 ` Kaneda, Erik
2020-06-12 12:05 ` Rafael J. Wysocki [this message]
2020-06-13 19:28 ` Rafael J. Wysocki
2020-06-15 19:06 ` Dan Williams
2020-06-10 12:22 ` [RFT][PATCH 3/3] ACPI: OSL: Define ACPI_OS_MAP_MEMORY_FAST_PATH() Rafael J. Wysocki
2020-06-13 19:19 ` [RFT][PATCH 0/3] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki
2020-06-22 13:50 ` [RFT][PATCH v2 0/4] " Rafael J. Wysocki
2020-06-22 13:52 ` [RFT][PATCH v2 1/4] ACPICA: Defer unmapping of opregion memory if supported by OS Rafael J. Wysocki
2020-06-22 13:53 ` [RFT][PATCH v2 2/4] ACPI: OSL: Add support for deferred unmapping of ACPI memory Rafael J. Wysocki
2020-06-22 14:56 ` Andy Shevchenko
2020-06-22 15:27 ` Rafael J. Wysocki
2020-06-22 15:46 ` Andy Shevchenko
2020-06-22 14:01 ` [RFT][PATCH v2 3/4] ACPICA: Preserve memory opregion mappings if supported by OS Rafael J. Wysocki
2020-06-26 22:53 ` Kaneda, Erik
2020-06-29 13:02 ` Rafael J. Wysocki
2020-06-22 14:02 ` [RFT][PATCH v2 4/4] ACPI: OSL: Implement acpi_os_map_memory_fast_path() Rafael J. Wysocki
2020-06-26 17:28 ` [RFT][PATCH v3 0/4] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki
2020-06-26 17:31 ` [RFT][PATCH v3 1/4] ACPICA: Take deferred unmapping of memory into account Rafael J. Wysocki
2020-06-26 17:31 ` [RFT][PATCH v3 2/4] ACPI: OSL: Implement deferred unmapping of ACPI memory Rafael J. Wysocki
2020-06-26 17:32 ` [RFT][PATCH v3 3/4] ACPICA: Preserve memory opregion mappings if supported by OS Rafael J. Wysocki
2020-06-26 17:33 ` [RFT][PATCH v3 4/4] ACPI: OSL: Implement acpi_os_map_memory_fast_path() Rafael J. Wysocki
2020-06-26 18:41 ` [RFT][PATCH v3 0/4] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Dan Williams
2020-06-28 17:09 ` Rafael J. Wysocki
2020-06-29 20:46 ` Dan Williams
2020-06-30 11:04 ` Rafael J. Wysocki
2020-06-29 16:31 ` [PATCH v4 0/2] " Rafael J. Wysocki
2020-06-29 16:33 ` [PATCH v4 1/2] ACPI: OSL: Implement deferred unmapping of ACPI memory Rafael J. Wysocki
2020-06-29 16:33 ` [PATCH v4 2/2] ACPICA: Preserve memory opregion mappings Rafael J. Wysocki
2020-06-29 20:57 ` Al Stone
2020-06-30 11:44 ` Rafael J. Wysocki
2020-06-30 15:31 ` Al Stone
2020-06-30 15:52 ` Rafael J. Wysocki
2020-06-30 19:57 ` Al Stone
2020-07-16 19:22 ` Verma, Vishal L
2020-07-19 19:14 ` Rafael J. Wysocki
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