From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6829DC433DF for ; Sat, 13 Jun 2020 19:28:58 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4B1B52074D for ; Sat, 13 Jun 2020 19:28:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4B1B52074D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 1D7D21007A3DC; Sat, 13 Jun 2020 12:28:58 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=79.96.170.134; helo=cloudserver094114.home.pl; envelope-from=rjw@rjwysocki.net; receiver= Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 6479410106A08 for ; Sat, 13 Jun 2020 12:28:55 -0700 (PDT) Received: from 89-77-60-66.dynamic.chello.pl (89.77.60.66) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.415) id db32435290b12ab0; Sat, 13 Jun 2020 21:28:53 +0200 From: "Rafael J. Wysocki" To: "Kaneda, Erik" Subject: Re: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on interpreter exit Date: Sat, 13 Jun 2020 21:28:52 +0200 Message-ID: <34641620.ChEHEh4gq6@kreacher> In-Reply-To: References: <158889473309.2292982.18007035454673387731.stgit@dwillia2-desk3.amr.corp.intel.com>

MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Message-ID-Hash: H6PF5RLMDLOQPICTMHFJATZJE65GC5OU X-Message-ID-Hash: H6PF5RLMDLOQPICTMHFJATZJE65GC5OU X-MailFrom: rjw@rjwysocki.net X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: "Rafael J. Wysocki" , "Wysocki, Rafael J" , Len Brown , Borislav Petkov , James Morse , Myron Stowe , Andy Shevchenko , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "linux-nvdimm@lists.01.org" , "Moore, Robert" X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Transfer-Encoding: 7bit On Friday, June 12, 2020 2:05:01 PM CEST Rafael J. Wysocki wrote: > On Fri, Jun 12, 2020 at 2:12 AM Kaneda, Erik wrote: > > > > > > > > > -----Original Message----- > > > From: Rafael J. Wysocki > > > Sent: Wednesday, June 10, 2020 5:22 AM > > > To: Williams, Dan J > > > Cc: Kaneda, Erik ; Wysocki, Rafael J > > > ; Len Brown ; Borislav > > > Petkov ; Weiny, Ira ; James Morse > > > ; Myron Stowe ; > > > Andy Shevchenko ; linux- > > > kernel@vger.kernel.org; linux-acpi@vger.kernel.org; linux- > > > nvdimm@lists.01.org; Moore, Robert > > > Subject: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on > > > interpreter exit > > > > > > From: "Rafael J. Wysocki" > > > > > > 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 > > > --- > > > 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 > > > #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. After writing the above I started to think about the extra changes needed to improve that and I realized that it would take making the OS layer support deferred memory unmapping, such that the unused mappings would be queued up for later removal and then released in one go at a suitable time. However, that would be sufficient to address the issue addressed by this series, because the deferred unmapping could be used in acpi_ev_system_memory_region_setup() right away and that would be a much simpler change than the one made in patch [1/3]. So I went ahead and implemented this and the result is there in the acpica-osl branch in my tree, but it hasn't been built yet, so caveat emptor. Anyway, please feel free to have a look at it still. Cheers! _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6777EC433E0 for ; Sat, 13 Jun 2020 19:28:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 450692074D for ; Sat, 13 Jun 2020 19:28:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726323AbgFMT24 (ORCPT ); Sat, 13 Jun 2020 15:28:56 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:46292 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726304AbgFMT24 (ORCPT ); Sat, 13 Jun 2020 15:28:56 -0400 Received: from 89-77-60-66.dynamic.chello.pl (89.77.60.66) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.415) id db32435290b12ab0; Sat, 13 Jun 2020 21:28:53 +0200 From: "Rafael J. Wysocki" To: "Kaneda, Erik" Cc: "Rafael J. Wysocki" , "Williams, Dan J" , "Wysocki, Rafael J" , Len Brown , Borislav Petkov , "Weiny, Ira" , James Morse , Myron Stowe , Andy Shevchenko , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "linux-nvdimm@lists.01.org" , "Moore, Robert" Subject: Re: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on interpreter exit Date: Sat, 13 Jun 2020 21:28:52 +0200 Message-ID: <34641620.ChEHEh4gq6@kreacher> In-Reply-To: References: <158889473309.2292982.18007035454673387731.stgit@dwillia2-desk3.amr.corp.intel.com>

MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Friday, June 12, 2020 2:05:01 PM CEST Rafael J. Wysocki wrote: > On Fri, Jun 12, 2020 at 2:12 AM Kaneda, Erik wrote: > > > > > > > > > -----Original Message----- > > > From: Rafael J. Wysocki > > > Sent: Wednesday, June 10, 2020 5:22 AM > > > To: Williams, Dan J > > > Cc: Kaneda, Erik ; Wysocki, Rafael J > > > ; Len Brown ; Borislav > > > Petkov ; Weiny, Ira ; James Morse > > > ; Myron Stowe ; > > > Andy Shevchenko ; linux- > > > kernel@vger.kernel.org; linux-acpi@vger.kernel.org; linux- > > > nvdimm@lists.01.org; Moore, Robert > > > Subject: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on > > > interpreter exit > > > > > > From: "Rafael J. Wysocki" > > > > > > 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 > > > --- > > > 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 > > > #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. After writing the above I started to think about the extra changes needed to improve that and I realized that it would take making the OS layer support deferred memory unmapping, such that the unused mappings would be queued up for later removal and then released in one go at a suitable time. However, that would be sufficient to address the issue addressed by this series, because the deferred unmapping could be used in acpi_ev_system_memory_region_setup() right away and that would be a much simpler change than the one made in patch [1/3]. So I went ahead and implemented this and the result is there in the acpica-osl branch in my tree, but it hasn't been built yet, so caveat emptor. Anyway, please feel free to have a look at it still. Cheers!