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From: Alexander Duyck <alexander.duyck@gmail.com>
To: virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org,
	mst@redhat.com, linux-kernel@vger.kernel.org,
	willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org,
	akpm@linux-foundation.org, mgorman@techsingularity.net,
	vbabka@suse.cz
Cc: yang.zhang.wz@gmail.com, nitesh@redhat.com,
	konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com,
	riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com,
	wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
	dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com,
	osalvador@suse.de
Subject: [PATCH v15 QEMU 4/3 RFC] memory: Add support for MADV_FREE as mechanism to lazy discard pages
Date: Thu, 05 Dec 2019 08:26:21 -0800	[thread overview]
Message-ID: <20191205162506.19787.9449.stgit@localhost.localdomain> (raw)
In-Reply-To: <20191205161928.19548.41654.stgit@localhost.localdomain>

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Add support for the MADV_FREE advice argument when discarding pages.
Specifically we add an option to perform a lazy discard for use with free
page reporting as this allows us to avoid expensive page zeroing in the
case that the system is not under memory pressure.

To enable this I simply extended the ram_block_discard_range function to
add an extra parameter for "lazy" freeing. I then renamed the function,
wrapped it in a function defined using the original name and defaulting
lazy to false. From there I created a second wrapper for
ram_block_free_range and updated the page reporting code to use that.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 exec.c                     |   39 +++++++++++++++++++++++++++------------
 hw/virtio/virtio-balloon.c |    2 +-
 include/exec/cpu-common.h  |    1 +
 3 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/exec.c b/exec.c
index ffdb5185353b..14eda993058c 100644
--- a/exec.c
+++ b/exec.c
@@ -3843,15 +3843,8 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
     return ret;
 }
 
-/*
- * Unmap pages of memory from start to start+length such that
- * they a) read as 0, b) Trigger whatever fault mechanism
- * the OS provides for postcopy.
- * The pages must be unmapped by the end of the function.
- * Returns: 0 on success, none-0 on failure
- *
- */
-int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
+static int __ram_block_discard_range(RAMBlock *rb, uint64_t start,
+                                     size_t length, bool lazy)
 {
     int ret = -1;
 
@@ -3904,13 +3897,18 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
 #endif
         }
         if (need_madvise) {
-            /* For normal RAM this causes it to be unmapped,
+#ifdef CONFIG_MADVISE
+#ifdef MADV_FREE
+            int advice = (lazy && !need_fallocate) ? MADV_FREE : MADV_DONTNEED;
+#else
+            int advice = MADV_DONTNEED;
+#endif
+            /* For normal RAM this causes it to be lazy freed or unmapped,
              * for shared memory it causes the local mapping to disappear
              * and to fall back on the file contents (which we just
              * fallocate'd away).
              */
-#if defined(CONFIG_MADVISE)
-            ret =  madvise(host_startaddr, length, MADV_DONTNEED);
+            ret =  madvise(host_startaddr, length, advice);
             if (ret) {
                 ret = -errno;
                 error_report("ram_block_discard_range: Failed to discard range "
@@ -3938,6 +3936,23 @@ err:
     return ret;
 }
 
+/*
+ * Unmap pages of memory from start to start+length such that
+ * they a) read as 0, b) Trigger whatever fault mechanism
+ * the OS provides for postcopy.
+ * The pages must be unmapped by the end of the function.
+ * Returns: 0 on success, none-0 on failure
+ *
+ */
+int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
+{
+    return __ram_block_discard_range(rb, start, length, false);
+}
+
+int ram_block_free_range(RAMBlock *rb, uint64_t start, size_t length)
+{
+    return __ram_block_discard_range(rb, start, length, true);
+}
 bool ramblock_is_pmem(RAMBlock *rb)
 {
     return rb->flags & RAM_PMEM;
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 47f253d016db..b904bdde8b1b 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -346,7 +346,7 @@ static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq)
             if ((ram_offset | size) & (rb_page_size - 1))
                 continue;
 
-            ram_block_discard_range(rb, ram_offset, size);
+            ram_block_free_range(rb, ram_offset, size);
         }
 
         virtqueue_push(vq, elem, 0);
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 81753bbb3431..2bbd26784c63 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -104,6 +104,7 @@ typedef int (RAMBlockIterFunc)(RAMBlock *rb, void *opaque);
 
 int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
 int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length);
+int ram_block_free_range(RAMBlock *rb, uint64_t start, size_t length);
 
 #endif
 


  parent reply	other threads:[~2019-12-05 16:26 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-05 16:22 [PATCH v15 0/7] mm / virtio: Provide support for free page reporting Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 1/7] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 2/7] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 3/7] mm: Add function __putback_isolated_page Alexander Duyck
2019-12-16 11:36   ` David Hildenbrand
2019-12-16 16:22     ` Alexander Duyck
2019-12-17 10:58       ` David Hildenbrand
2019-12-17 16:26         ` Alexander Duyck
2019-12-17 17:24           ` David Hildenbrand
2019-12-17 18:24             ` Alexander Duyck
2019-12-17 18:46               ` David Hildenbrand
2019-12-17 21:50                 ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 4/7] mm: Introduce Reported pages Alexander Duyck
2019-12-16 10:17   ` Nitesh Narayan Lal
2019-12-16 16:28     ` Alexander Duyck
2019-12-17  8:55       ` Nitesh Narayan Lal
2019-12-17 16:31         ` Alexander Duyck
2019-12-18  7:31           ` Mel Gorman
2019-12-16 11:44   ` Nitesh Narayan Lal
2019-12-16 16:10     ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 5/7] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-12-13  7:03   ` Michael S. Tsirkin
2019-12-05 16:22 ` [PATCH v15 6/7] virtio-balloon: Add support for providing free page reports to host Alexander Duyck
2019-12-13  7:08   ` Michael S. Tsirkin
2019-12-13 16:35     ` Alexander Duyck
2019-12-15  9:29       ` Michael S. Tsirkin
2019-12-13 10:15   ` David Hildenbrand
2019-12-13 16:37     ` Alexander Duyck
2019-12-05 16:23 ` [PATCH v15 7/7] mm: Add free page reporting documentation Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
2019-12-05 16:26 ` Alexander Duyck [this message]
2019-12-12 23:47 ` [PATCH v15 0/7] mm / virtio: Provide support for free " Alexander Duyck
2019-12-13 10:00 ` David Hildenbrand
2019-12-13 11:08   ` Mel Gorman
2019-12-13 16:59     ` Alexander Duyck
2019-12-13 16:46   ` Alexander Duyck
2019-12-16 12:21     ` David Hildenbrand

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