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(2001-1c00-0c32-7800-5bfa-a036-83f0-f9ec.cable.dynamic.v6.ziggo.nl. [2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id i12-20020aa7c70c000000b0050bd7267a5csm7905686edq.58.2023.05.16.01.31.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 May 2023 01:31:59 -0700 (PDT) Message-ID: Date: Tue, 16 May 2023 10:31:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH] ACPI: scan: Reduce overhead related to devices with dependencies To: "Rafael J. Wysocki" , Linux ACPI Cc: LKML , Sakari Ailus References: <2694293.mvXUDI8C0e@kreacher> Content-Language: en-US, nl From: Hans de Goede In-Reply-To: <2694293.mvXUDI8C0e@kreacher> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Hi Rafael, On 5/15/23 18:30, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > Notice that all of the objects for which the acpi_scan_check_dep() > return value is greater than 0 are present in acpi_dep_list as consumers > (there may be multiple entries for one object, but that is not a > problem), so after carrying out the initial ACPI namespace walk in which > devices with dependencies are skipped, acpi_bus_scan() can simply walk > acpi_dep_list and enumerate all of the unique consumer objects from > there and their descendants instead of walking the entire target branch > of the ACPI namespace and looking for device objects that have not been > enumerated yet in it. > > Because walking acpi_dep_list is generally less overhead than walking > the entire ACPI namespace, use the observation above to reduce the > system initialization overhead related to ACPI, which is particularly > important on large systems. > > Signed-off-by: Rafael J. Wysocki > --- > drivers/acpi/scan.c | 79 +++++++++++++++++++++++++++++++++++------------- > include/acpi/acpi_bus.h | 2 + > 2 files changed, 61 insertions(+), 20 deletions(-) > > Index: linux-pm/include/acpi/acpi_bus.h > =================================================================== > --- linux-pm.orig/include/acpi/acpi_bus.h > +++ linux-pm/include/acpi/acpi_bus.h > @@ -289,6 +289,8 @@ struct acpi_dep_data { > acpi_handle supplier; > acpi_handle consumer; > bool honor_dep; > + bool met; > + bool free_when_met; > }; > > /* Performance Management */ > Index: linux-pm/drivers/acpi/scan.c > =================================================================== > --- linux-pm.orig/drivers/acpi/scan.c > +++ linux-pm/drivers/acpi/scan.c > @@ -2029,8 +2029,6 @@ static u32 acpi_scan_check_dep(acpi_hand > return count; > } > > -static bool acpi_bus_scan_second_pass; > - > static acpi_status acpi_bus_check_add(acpi_handle handle, bool check_dep, > struct acpi_device **adev_p) > { > @@ -2050,10 +2048,8 @@ static acpi_status acpi_bus_check_add(ac > return AE_OK; > > /* Bail out if there are dependencies. */ > - if (acpi_scan_check_dep(handle, check_dep) > 0) { > - acpi_bus_scan_second_pass = true; > + if (acpi_scan_check_dep(handle, check_dep) > 0) > return AE_CTRL_DEPTH; > - } > > fallthrough; > case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */ > @@ -2301,6 +2297,12 @@ static bool acpi_scan_clear_dep_queue(st > return true; > } > > +static void acpi_scan_delete_dep_data(struct acpi_dep_data *dep) > +{ > + list_del(&dep->node); > + kfree(dep); > +} > + > static int acpi_scan_clear_dep(struct acpi_dep_data *dep, void *data) > { > struct acpi_device *adev = acpi_get_acpi_dev(dep->consumer); > @@ -2311,8 +2313,10 @@ static int acpi_scan_clear_dep(struct ac > acpi_dev_put(adev); > } > > - list_del(&dep->node); > - kfree(dep); > + if (dep->free_when_met) > + acpi_scan_delete_dep_data(dep); > + else > + dep->met = true; > > return 0; > } > @@ -2406,6 +2410,53 @@ struct acpi_device *acpi_dev_get_next_co > } > EXPORT_SYMBOL_GPL(acpi_dev_get_next_consumer_dev); > > +static void acpi_scan_postponed_branch(acpi_handle handle) > +{ > + struct acpi_device *adev = NULL; > + > + if (ACPI_FAILURE(acpi_bus_check_add(handle, false, &adev))) > + return; > + > + acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX, > + acpi_bus_check_add_2, NULL, NULL, (void **)&adev); > + acpi_bus_attach(adev, NULL); > +} > + > +static void acpi_scan_postponed(void) > +{ > + struct acpi_dep_data *dep, *tmp; > + > + mutex_lock(&acpi_dep_list_lock); > + > + list_for_each_entry_safe(dep, tmp, &acpi_dep_list, node) { > + acpi_handle handle = dep->consumer; > + > + /* > + * Even though the lock is released here, tmp is guaranteed to > + * be valid, because none of the list entries following dep is > + * marked as "free when met" and so they cannot be deleted. > + */ > + mutex_unlock(&acpi_dep_list_lock); > + > + /* > + * In case there are multiple acpi_dep_list entries with the > + * same consumer, skip the current entry if the consumer device > + * object corresponding to it is present already. > + */ > + if (!acpi_fetch_acpi_dev(handle)) > + acpi_scan_postponed_branch(handle); acpi_fetch_acpi_dev(handle) does not need/take the acpi_dep_list_lock, so you can avoid a needless unlock/lock in case acpi_fetch_acpi_dev(handle) finds a device already, which will happen quite regular since devices with _DEP lists regularly have more then 1 dep so they will be present as consumer on the _DEP list more then once. So maybe: list_for_each_entry_safe(dep, tmp, &acpi_dep_list, node) { acpi_handle handle = dep->consumer; struct acpi_device *device = acpi_fetch_acpi_dev(handle); /* * In case there are multiple acpi_dep_list entries with the * same consumer, skip scanning the current entry if the consumer * device object corresponding to it is present already. */ if (device) goto check_dep; /* * Even though the lock is released here, tmp is guaranteed to * be valid, because none of the list entries following dep is * marked as "free when met" and so they cannot be deleted. */ mutex_unlock(&acpi_dep_list_lock); acpi_scan_postponed_branch(handle); mutex_lock(&acpi_dep_list_lock); check_dep: if (dep->met) acpi_scan_delete_dep_data(dep); else dep->free_when_met = true; } ? Regards, Hans > + > + mutex_unlock(&acpi_dep_list_lock); > +} > + > /** > * acpi_bus_scan - Add ACPI device node objects in a given namespace scope. > * @handle: Root of the namespace scope to scan. > @@ -2424,8 +2475,6 @@ int acpi_bus_scan(acpi_handle handle) > { > struct acpi_device *device = NULL; > > - acpi_bus_scan_second_pass = false; > - > /* Pass 1: Avoid enumerating devices with missing dependencies. */ > > if (ACPI_SUCCESS(acpi_bus_check_add(handle, true, &device))) > @@ -2438,19 +2487,9 @@ int acpi_bus_scan(acpi_handle handle) > > acpi_bus_attach(device, (void *)true); > > - if (!acpi_bus_scan_second_pass) > - return 0; > - > /* Pass 2: Enumerate all of the remaining devices. */ > > - device = NULL; > - > - if (ACPI_SUCCESS(acpi_bus_check_add(handle, false, &device))) > - acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX, > - acpi_bus_check_add_2, NULL, NULL, > - (void **)&device); > - > - acpi_bus_attach(device, NULL); > + acpi_scan_postponed(); > > return 0; > } > > >