From: Yang Shi <yang.shi@linux.alibaba.com>
To: akpm@linux-foundation.org
Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [RFC PATCH 1/8] mm: mmap: unmap large mapping by section
Date: Wed, 21 Mar 2018 05:31:19 +0800 [thread overview]
Message-ID: <1521581486-99134-2-git-send-email-yang.shi@linux.alibaba.com> (raw)
In-Reply-To: <1521581486-99134-1-git-send-email-yang.shi@linux.alibaba.com>
When running some mmap/munmap scalability tests with large memory (i.e.
> 300GB), the below hung task issue may happen occasionally.
INFO: task ps:14018 blocked for more than 120 seconds.
Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
ps D 0 14018 1 0x00000004
ffff885582f84000 ffff885e8682f000 ffff880972943000 ffff885ebf499bc0
ffff8828ee120000 ffffc900349bfca8 ffffffff817154d0 0000000000000040
00ffffff812f872a ffff885ebf499bc0 024000d000948300 ffff880972943000
Call Trace:
[<ffffffff817154d0>] ? __schedule+0x250/0x730
[<ffffffff817159e6>] schedule+0x36/0x80
[<ffffffff81718560>] rwsem_down_read_failed+0xf0/0x150
[<ffffffff81390a28>] call_rwsem_down_read_failed+0x18/0x30
[<ffffffff81717db0>] down_read+0x20/0x40
[<ffffffff812b9439>] proc_pid_cmdline_read+0xd9/0x4e0
[<ffffffff81253c95>] ? do_filp_open+0xa5/0x100
[<ffffffff81241d87>] __vfs_read+0x37/0x150
[<ffffffff812f824b>] ? security_file_permission+0x9b/0xc0
[<ffffffff81242266>] vfs_read+0x96/0x130
[<ffffffff812437b5>] SyS_read+0x55/0xc0
[<ffffffff8171a6da>] entry_SYSCALL_64_fastpath+0x1a/0xc5
It is because munmap holds mmap_sem from very beginning to all the way
down to the end, and doesn't release it in the middle. When unmapping
large mapping, it may take long time (take ~18 seconds to unmap 320GB
mapping with every single page mapped on an idle machine).
Since unmapping does't require any atomicity, so here unmap large
mapping (> HPAGE_PUD_SIZE) section by section, and release mmap_sem for
unmapping every HPAGE_PUD_SIZE if mmap_sem is contended and the call
path is fine to be interrupted controlled by "atomic", newly added
parameter to do_munmap(). "false" means it is fine to do unlock/relock
to mmap_sem in the middle.
Not only munmap may benefit from this change, but also
mremap/shm since they all call do_munmap() to do the real work.
The below is some regression and performance data collected on a machine
with 32 cores of E5-2680 @ 2.70GHz and 384GB memory.
Measurement of SyS_munmap() execution time:
size pristine patched delta
80GB 5008377 us 4905841 us -2%
160GB 9129243 us 9145306 us +0.18%
320GB 17915310 us 17990174 us +0.42%
Throughput of page faults (#/s) with vm-scalability:
pristine patched delta
mmap-pread-seq 554894 563517 +1.6%
mmap-pread-seq-mt 581232 580772 -0.079%
mmap-xread-seq-mt 99182 105400 +6.3%
Throughput of page faults (#/s) with the below stress-ng test:
stress-ng --mmap 0 --mmap-bytes 80G --mmap-file --metrics --perf
--timeout 600s
pristine patched delta
100165 108396 +8.2%
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
include/linux/mm.h | 2 +-
mm/mmap.c | 40 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ad06d42..2e447d4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2212,7 +2212,7 @@ extern unsigned long do_mmap(struct file *file, unsigned long addr,
vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
struct list_head *uf);
extern int do_munmap(struct mm_struct *, unsigned long, size_t,
- struct list_head *uf);
+ struct list_head *uf, bool atomic);
static inline unsigned long
do_mmap_pgoff(struct file *file, unsigned long addr,
diff --git a/mm/mmap.c b/mm/mmap.c
index 9efdc021..ad6ae7a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2632,8 +2632,8 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
* work. This now handles partial unmappings.
* Jeremy Fitzhardinge <jeremy@goop.org>
*/
-int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
- struct list_head *uf)
+static int do_munmap_range(struct mm_struct *mm, unsigned long start,
+ size_t len, struct list_head *uf)
{
unsigned long end;
struct vm_area_struct *vma, *prev, *last;
@@ -2733,6 +2733,42 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
return 0;
}
+int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
+ struct list_head *uf, bool atomic)
+{
+ int ret = 0;
+ size_t step = HPAGE_PUD_SIZE;
+
+ /*
+ * unmap large mapping (> huge pud size) section by section
+ * in order to give mmap_sem waiters a chance to acquire it.
+ */
+ if (len <= step)
+ ret = do_munmap_range(mm, start, len, uf);
+ else {
+ do {
+ ret = do_munmap_range(mm, start, step, uf);
+ if (ret < 0)
+ break;
+
+ if (rwsem_is_contended(&mm->mmap_sem) && !atomic &&
+ need_resched()) {
+ VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+ up_write(&mm->mmap_sem);
+ cond_resched();
+ down_write(&mm->mmap_sem);
+ }
+
+ start += step;
+ len -= step;
+ if (len <= step)
+ step = len;
+ } while (len > 0);
+ }
+
+ return ret;
+}
+
int vm_munmap(unsigned long start, size_t len)
{
int ret;
--
1.8.3.1
next prev parent reply other threads:[~2018-03-20 21:31 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-20 21:31 [RFC PATCH 0/8] Drop mmap_sem during unmapping large map Yang Shi
2018-03-20 21:31 ` Yang Shi [this message]
2018-03-21 13:08 ` [RFC PATCH 1/8] mm: mmap: unmap large mapping by section Michal Hocko
2018-03-21 16:31 ` Yang Shi
2018-03-21 17:29 ` Matthew Wilcox
2018-03-21 21:45 ` Yang Shi
2018-03-21 22:15 ` Matthew Wilcox
2018-03-21 22:40 ` Yang Shi
2018-03-21 22:46 ` Matthew Wilcox
2018-03-22 15:32 ` Laurent Dufour
2018-03-22 15:40 ` Matthew Wilcox
2018-03-22 15:54 ` Laurent Dufour
2018-03-22 16:05 ` Matthew Wilcox
2018-03-22 16:18 ` Laurent Dufour
2018-03-22 16:46 ` Yang Shi
2018-03-23 13:03 ` Laurent Dufour
2018-03-22 16:51 ` Matthew Wilcox
2018-03-22 16:49 ` Yang Shi
2018-03-22 17:34 ` Yang Shi
2018-03-22 18:48 ` Matthew Wilcox
2018-03-24 18:24 ` Jerome Glisse
2018-03-21 13:14 ` Michal Hocko
2018-03-21 16:50 ` Yang Shi
2018-03-21 17:16 ` Yang Shi
2018-03-21 21:23 ` Michal Hocko
2018-03-21 22:36 ` Yang Shi
2018-03-22 9:10 ` Michal Hocko
2018-03-22 16:06 ` Yang Shi
2018-03-22 16:12 ` Michal Hocko
2018-03-22 16:13 ` Matthew Wilcox
2018-03-22 16:28 ` Laurent Dufour
2018-03-22 16:36 ` David Laight
2018-03-20 21:31 ` [RFC PATCH 2/8] mm: mmap: pass atomic parameter to do_munmap() call sites Yang Shi
2018-03-20 21:31 ` [RFC PATCH 3/8] mm: mremap: pass atomic parameter to do_munmap() Yang Shi
2018-03-20 21:31 ` [RFC PATCH 4/8] mm: nommu: add " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 5/8] ipc: shm: pass " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 6/8] fs: proc/vmcore: " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 7/8] x86: mpx: " Yang Shi
2018-03-20 22:35 ` Thomas Gleixner
2018-03-21 16:53 ` Yang Shi
2018-03-20 21:31 ` [RFC PATCH 8/8] x86: vma: " Yang Shi
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