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authorUladzislau Rezki (Sony) <urezki@gmail.com>2022-03-22 14:42:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 15:57:05 -0700
commit690467c81b1a49de38a4b89eedc0ae85015f4c79 (patch)
tree166647762f19a1e8cc98b0b7a1c309f47161c887 /mm/vmalloc.c
parent651d55ce096543c52f7e589d04dfa7393f90ff47 (diff)
mm/vmalloc: Move draining areas out of caller context
A caller initiates the drain procces from its context once the drain threshold is reached or passed. There are at least two drawbacks of doing so: a) a caller can be a high-prio or RT task. In that case it can stuck in doing the actual drain of all lazily freed areas. This is not optimal because such tasks usually are latency sensitive where the control should be returned back as soon as possible in order to drive such workloads in time. See 96e2db456135 ("mm/vmalloc: rework the drain logic") b) It is not safe to call vfree() during holding a spinlock due to the vmap_purge_lock mutex. The was a report about this from Zeal Robot <zealci@zte.com.cn> here: https://lore.kernel.org/all/20211222081026.484058-1-chi.minghao@zte.com.cn Moving the drain to the separate work context addresses those issues. v1->v2: - Added prefix "_work" to the drain worker function. v2->v3: - Remove the drain_vmap_work_in_progress. Extra queuing is expectable under heavy load but it can be disregarded because a work will bail out if nothing to be done. Link: https://lkml.kernel.org/r/20220131144058.35608-1-urezki@gmail.com Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Matthew Wilcox <willy@infradead.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Vasily Averin <vvs@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
-rw-r--r--mm/vmalloc.c30
1 files changed, 17 insertions, 13 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b8aa02293d57..6231cfa15f7f 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -791,6 +791,8 @@ RB_DECLARE_CALLBACKS_MAX(static, free_vmap_area_rb_augment_cb,
static void purge_vmap_area_lazy(void);
static BLOCKING_NOTIFIER_HEAD(vmap_notify_list);
+static void drain_vmap_area_work(struct work_struct *work);
+static DECLARE_WORK(drain_vmap_work, drain_vmap_area_work);
static atomic_long_t nr_vmalloc_pages;
@@ -1718,18 +1720,6 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
}
/*
- * Kick off a purge of the outstanding lazy areas. Don't bother if somebody
- * is already purging.
- */
-static void try_purge_vmap_area_lazy(void)
-{
- if (mutex_trylock(&vmap_purge_lock)) {
- __purge_vmap_area_lazy(ULONG_MAX, 0);
- mutex_unlock(&vmap_purge_lock);
- }
-}
-
-/*
* Kick off a purge of the outstanding lazy areas.
*/
static void purge_vmap_area_lazy(void)
@@ -1740,6 +1730,20 @@ static void purge_vmap_area_lazy(void)
mutex_unlock(&vmap_purge_lock);
}
+static void drain_vmap_area_work(struct work_struct *work)
+{
+ unsigned long nr_lazy;
+
+ do {
+ mutex_lock(&vmap_purge_lock);
+ __purge_vmap_area_lazy(ULONG_MAX, 0);
+ mutex_unlock(&vmap_purge_lock);
+
+ /* Recheck if further work is required. */
+ nr_lazy = atomic_long_read(&vmap_lazy_nr);
+ } while (nr_lazy > lazy_max_pages());
+}
+
/*
* Free a vmap area, caller ensuring that the area has been unmapped
* and flush_cache_vunmap had been called for the correct range
@@ -1766,7 +1770,7 @@ static void free_vmap_area_noflush(struct vmap_area *va)
/* After this point, we may free va at any time */
if (unlikely(nr_lazy > lazy_max_pages()))
- try_purge_vmap_area_lazy();
+ schedule_work(&drain_vmap_work);
}
/*