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mm: turn vmap_purge_lock into a mutex 

The purge_lock spinlock causes high latencies with non RT kernel.  This
has been reported multiple times on lkml [1] [2] and affects
applications like audio.

This patch replaces it with a mutex to allow preemption while holding
the lock.

Thanks to Joel Fernandes for the detailed report and analysis as well as
an earlier attempt at fixing this issue.

[1] http://lists.openwall.net/linux-kernel/2016/03/23/29
[2] https://lkml.org/lkml/2016/10/9/59

Link: http://lkml.kernel.org/r/1479474236-4139-10-git-send-email-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jisheng Zhang <jszhang@marvell.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: John Dias <joaodias@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Christoph Hellwig 2016-12-12 16:44:23 -08:00 committed by Linus Torvalds
parent 5803ed292e
commit f9e0997767
1 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
mm/vmalloc.c
View File

@ -606,7 +606,7 @@ static atomic_t vmap_lazy_nr = ATOMIC_INIT(0);
* by this look, but we want to avoid concurrent calls for performance * by this look, but we want to avoid concurrent calls for performance
* reasons and to make the pcpu_get_vm_areas more deterministic. * reasons and to make the pcpu_get_vm_areas more deterministic.
*/ */
static DEFINE_SPINLOCK(vmap_purge_lock); static DEFINE_MUTEX(vmap_purge_lock);
/* for per-CPU blocks */ /* for per-CPU blocks */
static void purge_fragmented_blocks_allcpus(void); static void purge_fragmented_blocks_allcpus(void);
@ -660,9 +660,9 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
*/ */
static void try_purge_vmap_area_lazy(void) static void try_purge_vmap_area_lazy(void)
{ {
if (spin_trylock(&vmap_purge_lock)) { if (mutex_trylock(&vmap_purge_lock)) {
__purge_vmap_area_lazy(ULONG_MAX, 0); __purge_vmap_area_lazy(ULONG_MAX, 0);
spin_unlock(&vmap_purge_lock); mutex_unlock(&vmap_purge_lock);
} }
} }
@ -671,10 +671,10 @@ static void try_purge_vmap_area_lazy(void)
*/ */
static void purge_vmap_area_lazy(void) static void purge_vmap_area_lazy(void)
{ {
spin_lock(&vmap_purge_lock); mutex_lock(&vmap_purge_lock);
purge_fragmented_blocks_allcpus(); purge_fragmented_blocks_allcpus();
__purge_vmap_area_lazy(ULONG_MAX, 0); __purge_vmap_area_lazy(ULONG_MAX, 0);
spin_unlock(&vmap_purge_lock); mutex_unlock(&vmap_purge_lock);
} }
/* /*
@ -1063,11 +1063,11 @@ void vm_unmap_aliases(void)
rcu_read_unlock(); rcu_read_unlock();
} }
spin_lock(&vmap_purge_lock); mutex_lock(&vmap_purge_lock);
purge_fragmented_blocks_allcpus(); purge_fragmented_blocks_allcpus();
if (!__purge_vmap_area_lazy(start, end) && flush) if (!__purge_vmap_area_lazy(start, end) && flush)
flush_tlb_kernel_range(start, end); flush_tlb_kernel_range(start, end);
spin_unlock(&vmap_purge_lock); mutex_unlock(&vmap_purge_lock);
} }
EXPORT_SYMBOL_GPL(vm_unmap_aliases); EXPORT_SYMBOL_GPL(vm_unmap_aliases);