From nobody Wed Dec 17 10:53:25 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 684A1CA0EF1 for ; Tue, 12 Sep 2023 16:28:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234460AbjILQ2X (ORCPT ); Tue, 12 Sep 2023 12:28:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236772AbjILQ2V (ORCPT ); Tue, 12 Sep 2023 12:28:21 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5D674170B for ; Tue, 12 Sep 2023 09:28:17 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5E170D75; Tue, 12 Sep 2023 09:28:54 -0700 (PDT) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id E5D763F738; Tue, 12 Sep 2023 09:28:15 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org Cc: will@kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, zhangzekun11@huawei.com, john.g.garry@oracle.com, dheerajkumar.srivastava@amd.com, jsnitsel@redhat.com Subject: [PATCH v3 1/2] iommu/iova: Make the rcache depot scale better Date: Tue, 12 Sep 2023 17:28:05 +0100 Message-Id: X-Mailer: git-send-email 2.39.2.101.g768bb238c484.dirty In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The algorithm in the original paper specifies the storage of full magazines in the depot as an unbounded list rather than a fixed-size array. It turns out to be pretty straightforward to do this in our implementation with no significant loss of efficiency. This allows the depot to scale up to the working set sizes of larger systems, while also potentially saving some memory on smaller ones too. Since this involves touching struct iova_magazine with the requisite care, we may as well reinforce the comment with a proper assertion too. Reviewed-by: John Garry Reviewed-by: Jerry Snitselaar Signed-off-by: Robin Murphy Tested-by: Ido Schimmel --- v3: No change drivers/iommu/iova.c | 65 ++++++++++++++++++++++++-------------------- 1 file changed, 35 insertions(+), 30 deletions(-) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 10b964600948..dd2309e9a6c5 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -622,15 +622,19 @@ EXPORT_SYMBOL_GPL(reserve_iova); /* * As kmalloc's buffer size is fixed to power of 2, 127 is chosen to * assure size of 'iova_magazine' to be 1024 bytes, so that no memory - * will be wasted. + * will be wasted. Since only full magazines are inserted into the depot, + * we don't need to waste PFN capacity on a separate list head either. */ #define IOVA_MAG_SIZE 127 -#define MAX_GLOBAL_MAGS 32 /* magazines per bin */ =20 struct iova_magazine { - unsigned long size; + union { + unsigned long size; + struct iova_magazine *next; + }; unsigned long pfns[IOVA_MAG_SIZE]; }; +static_assert(!(sizeof(struct iova_magazine) & (sizeof(struct iova_magazin= e) - 1))); =20 struct iova_cpu_rcache { spinlock_t lock; @@ -640,8 +644,7 @@ struct iova_cpu_rcache { =20 struct iova_rcache { spinlock_t lock; - unsigned long depot_size; - struct iova_magazine *depot[MAX_GLOBAL_MAGS]; + struct iova_magazine *depot; struct iova_cpu_rcache __percpu *cpu_rcaches; }; =20 @@ -717,6 +720,21 @@ static void iova_magazine_push(struct iova_magazine *m= ag, unsigned long pfn) mag->pfns[mag->size++] =3D pfn; } =20 +static struct iova_magazine *iova_depot_pop(struct iova_rcache *rcache) +{ + struct iova_magazine *mag =3D rcache->depot; + + rcache->depot =3D mag->next; + mag->size =3D IOVA_MAG_SIZE; + return mag; +} + +static void iova_depot_push(struct iova_rcache *rcache, struct iova_magazi= ne *mag) +{ + mag->next =3D rcache->depot; + rcache->depot =3D mag; +} + int iova_domain_init_rcaches(struct iova_domain *iovad) { unsigned int cpu; @@ -734,7 +752,6 @@ int iova_domain_init_rcaches(struct iova_domain *iovad) =20 rcache =3D &iovad->rcaches[i]; spin_lock_init(&rcache->lock); - rcache->depot_size =3D 0; rcache->cpu_rcaches =3D __alloc_percpu(sizeof(*cpu_rcache), cache_line_size()); if (!rcache->cpu_rcaches) { @@ -776,7 +793,6 @@ static bool __iova_rcache_insert(struct iova_domain *io= vad, struct iova_rcache *rcache, unsigned long iova_pfn) { - struct iova_magazine *mag_to_free =3D NULL; struct iova_cpu_rcache *cpu_rcache; bool can_insert =3D false; unsigned long flags; @@ -794,12 +810,7 @@ static bool __iova_rcache_insert(struct iova_domain *i= ovad, =20 if (new_mag) { spin_lock(&rcache->lock); - if (rcache->depot_size < MAX_GLOBAL_MAGS) { - rcache->depot[rcache->depot_size++] =3D - cpu_rcache->loaded; - } else { - mag_to_free =3D cpu_rcache->loaded; - } + iova_depot_push(rcache, cpu_rcache->loaded); spin_unlock(&rcache->lock); =20 cpu_rcache->loaded =3D new_mag; @@ -812,11 +823,6 @@ static bool __iova_rcache_insert(struct iova_domain *i= ovad, =20 spin_unlock_irqrestore(&cpu_rcache->lock, flags); =20 - if (mag_to_free) { - iova_magazine_free_pfns(mag_to_free, iovad); - iova_magazine_free(mag_to_free); - } - return can_insert; } =20 @@ -854,9 +860,9 @@ static unsigned long __iova_rcache_get(struct iova_rcac= he *rcache, has_pfn =3D true; } else { spin_lock(&rcache->lock); - if (rcache->depot_size > 0) { + if (rcache->depot) { iova_magazine_free(cpu_rcache->loaded); - cpu_rcache->loaded =3D rcache->depot[--rcache->depot_size]; + cpu_rcache->loaded =3D iova_depot_pop(rcache); has_pfn =3D true; } spin_unlock(&rcache->lock); @@ -895,9 +901,8 @@ static void free_iova_rcaches(struct iova_domain *iovad) struct iova_rcache *rcache; struct iova_cpu_rcache *cpu_rcache; unsigned int cpu; - int i, j; =20 - for (i =3D 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { + for (int i =3D 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { rcache =3D &iovad->rcaches[i]; if (!rcache->cpu_rcaches) break; @@ -907,8 +912,8 @@ static void free_iova_rcaches(struct iova_domain *iovad) iova_magazine_free(cpu_rcache->prev); } free_percpu(rcache->cpu_rcaches); - for (j =3D 0; j < rcache->depot_size; ++j) - iova_magazine_free(rcache->depot[j]); + while (rcache->depot) + iova_magazine_free(iova_depot_pop(rcache)); } =20 kfree(iovad->rcaches); @@ -942,16 +947,16 @@ static void free_global_cached_iovas(struct iova_doma= in *iovad) { struct iova_rcache *rcache; unsigned long flags; - int i, j; =20 - for (i =3D 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { + for (int i =3D 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { rcache =3D &iovad->rcaches[i]; spin_lock_irqsave(&rcache->lock, flags); - for (j =3D 0; j < rcache->depot_size; ++j) { - iova_magazine_free_pfns(rcache->depot[j], iovad); - iova_magazine_free(rcache->depot[j]); + while (rcache->depot) { + struct iova_magazine *mag =3D iova_depot_pop(rcache); + + iova_magazine_free_pfns(mag, iovad); + iova_magazine_free(mag); } - rcache->depot_size =3D 0; spin_unlock_irqrestore(&rcache->lock, flags); } } --=20 2.39.2.101.g768bb238c484.dirty From nobody Wed Dec 17 10:53:25 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83EECCA0EF2 for ; Tue, 12 Sep 2023 16:28:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236787AbjILQ2Z (ORCPT ); Tue, 12 Sep 2023 12:28:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236769AbjILQ2X (ORCPT ); Tue, 12 Sep 2023 12:28:23 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9850A1703 for ; Tue, 12 Sep 2023 09:28:19 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 89091C15; Tue, 12 Sep 2023 09:28:56 -0700 (PDT) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 1CBE73F738; Tue, 12 Sep 2023 09:28:17 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org Cc: will@kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, zhangzekun11@huawei.com, john.g.garry@oracle.com, dheerajkumar.srivastava@amd.com, jsnitsel@redhat.com Subject: [PATCH v3 2/2] iommu/iova: Manage the depot list size Date: Tue, 12 Sep 2023 17:28:06 +0100 Message-Id: <03170665c56d89c6ce6081246b47f68d4e483308.1694535580.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.39.2.101.g768bb238c484.dirty In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Automatically scaling the depot up to suit the peak capacity of a workload is all well and good, but it would be nice to have a way to scale it back down again if the workload changes. To that end, add backround reclaim that will gradually free surplus magazines if the depot size remains above a reasonable threshold for long enough. Reviewed-by: Jerry Snitselaar Signed-off-by: Robin Murphy Tested-by: Ido Schimmel --- v3: Make sure iova_depot_work_func() locking is IRQ-safe drivers/iommu/iova.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index dd2309e9a6c5..d30e453d0fb4 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -11,6 +11,7 @@ #include #include #include +#include =20 /* The anchor node sits above the top of the usable address space */ #define IOVA_ANCHOR ~0UL @@ -627,6 +628,8 @@ EXPORT_SYMBOL_GPL(reserve_iova); */ #define IOVA_MAG_SIZE 127 =20 +#define IOVA_DEPOT_DELAY msecs_to_jiffies(100) + struct iova_magazine { union { unsigned long size; @@ -644,8 +647,11 @@ struct iova_cpu_rcache { =20 struct iova_rcache { spinlock_t lock; + unsigned int depot_size; struct iova_magazine *depot; struct iova_cpu_rcache __percpu *cpu_rcaches; + struct iova_domain *iovad; + struct delayed_work work; }; =20 static struct iova_magazine *iova_magazine_alloc(gfp_t flags) @@ -726,6 +732,7 @@ static struct iova_magazine *iova_depot_pop(struct iova= _rcache *rcache) =20 rcache->depot =3D mag->next; mag->size =3D IOVA_MAG_SIZE; + rcache->depot_size--; return mag; } =20 @@ -733,6 +740,25 @@ static void iova_depot_push(struct iova_rcache *rcache= , struct iova_magazine *ma { mag->next =3D rcache->depot; rcache->depot =3D mag; + rcache->depot_size++; +} + +static void iova_depot_work_func(struct work_struct *work) +{ + struct iova_rcache *rcache =3D container_of(work, typeof(*rcache), work.w= ork); + struct iova_magazine *mag =3D NULL; + unsigned long flags; + + spin_lock_irqsave(&rcache->lock, flags); + if (rcache->depot_size > num_online_cpus()) + mag =3D iova_depot_pop(rcache); + spin_unlock_irqrestore(&rcache->lock, flags); + + if (mag) { + iova_magazine_free_pfns(mag, rcache->iovad); + iova_magazine_free(mag); + schedule_delayed_work(&rcache->work, IOVA_DEPOT_DELAY); + } } =20 int iova_domain_init_rcaches(struct iova_domain *iovad) @@ -752,6 +778,8 @@ int iova_domain_init_rcaches(struct iova_domain *iovad) =20 rcache =3D &iovad->rcaches[i]; spin_lock_init(&rcache->lock); + rcache->iovad =3D iovad; + INIT_DELAYED_WORK(&rcache->work, iova_depot_work_func); rcache->cpu_rcaches =3D __alloc_percpu(sizeof(*cpu_rcache), cache_line_size()); if (!rcache->cpu_rcaches) { @@ -812,6 +840,7 @@ static bool __iova_rcache_insert(struct iova_domain *io= vad, spin_lock(&rcache->lock); iova_depot_push(rcache, cpu_rcache->loaded); spin_unlock(&rcache->lock); + schedule_delayed_work(&rcache->work, IOVA_DEPOT_DELAY); =20 cpu_rcache->loaded =3D new_mag; can_insert =3D true; @@ -912,6 +941,7 @@ static void free_iova_rcaches(struct iova_domain *iovad) iova_magazine_free(cpu_rcache->prev); } free_percpu(rcache->cpu_rcaches); + cancel_delayed_work_sync(&rcache->work); while (rcache->depot) iova_magazine_free(iova_depot_pop(rcache)); } --=20 2.39.2.101.g768bb238c484.dirty