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iommu/iova: Manage the depot list size

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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 <jsnitsel@redhat.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/03170665c56d89c6ce6081246b47f68d4e483308.1694535580.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2023-09-12 17:28:06 +01:00 committed by Joerg Roedel
parent 911aa1245d
commit 233045378d
1 changed files with 30 additions and 0 deletions
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30
drivers/iommu/iova.c
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@ -11,6 +11,7 @@
#include <linux/smp.h>
#include <linux/bitops.h>
#include <linux/cpu.h>
#include <linux/workqueue.h>
/* 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
#define IOVA_DEPOT_DELAY msecs_to_jiffies(100)
struct iova_magazine {
union {
unsigned long size;
@ -644,8 +647,11 @@ struct iova_cpu_rcache {
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;
};
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)
rcache->depot = mag->next;
mag->size = IOVA_MAG_SIZE;
rcache->depot_size--;
return mag;
}
@ -733,6 +740,25 @@ static void iova_depot_push(struct iova_rcache *rcache, struct iova_magazine *ma
{
mag->next = rcache->depot;
rcache->depot = mag;
rcache->depot_size++;
}
static void iova_depot_work_func(struct work_struct *work)
{
struct iova_rcache *rcache = container_of(work, typeof(*rcache), work.work);
struct iova_magazine *mag = NULL;
unsigned long flags;
spin_lock_irqsave(&rcache->lock, flags);
if (rcache->depot_size > num_online_cpus())
mag = 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);
}
}
int iova_domain_init_rcaches(struct iova_domain *iovad)
@ -752,6 +778,8 @@ int iova_domain_init_rcaches(struct iova_domain *iovad)
rcache = &iovad->rcaches[i];
spin_lock_init(&rcache->lock);
rcache->iovad = iovad;
INIT_DELAYED_WORK(&rcache->work, iova_depot_work_func);
rcache->cpu_rcaches = __alloc_percpu(sizeof(*cpu_rcache),
cache_line_size());
if (!rcache->cpu_rcaches) {
@ -812,6 +840,7 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
spin_lock(&rcache->lock);
iova_depot_push(rcache, cpu_rcache->loaded);
spin_unlock(&rcache->lock);
schedule_delayed_work(&rcache->work, IOVA_DEPOT_DELAY);
cpu_rcache->loaded = new_mag;
can_insert = 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));
}