From: David Hildenbrand <david@redhat.com>
To: qemu-devel@nongnu.org
Cc: Igor Mammedov <imammedo@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>,
"Michael S . Tsirkin" <mst@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
David Hildenbrand <david@redhat.com>
Subject: [Qemu-devel] [PATCH v1 1/3] virtio-balloon: simplify deflate with pbp
Date: Fri, 19 Jul 2019 18:01:18 +0200 [thread overview]
Message-ID: <20190719160120.26581-2-david@redhat.com> (raw)
In-Reply-To: <20190719160120.26581-1-david@redhat.com>
Let's simplify this - the case we are optimizing for is very hard to
trigger and not worth the effort. If we're switching from inflation to
deflation, let's reset the pbp.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/virtio-balloon.c | 24 ++++--------------------
1 file changed, 4 insertions(+), 20 deletions(-)
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 9de3c030bf..287d5d4c97 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -121,7 +121,7 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
void *addr = memory_region_get_ram_ptr(mr) + offset;
RAMBlock *rb;
size_t rb_page_size;
- ram_addr_t ram_offset, host_page_base;
+ ram_addr_t ram_offset;
void *host_addr;
int ret;
@@ -129,26 +129,10 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
* host address? */
rb = qemu_ram_block_from_host(addr, false, &ram_offset);
rb_page_size = qemu_ram_pagesize(rb);
- host_page_base = ram_offset & ~(rb_page_size - 1);
-
- if (balloon->pbp
- && rb == balloon->pbp->rb
- && host_page_base == balloon->pbp->base) {
- int subpages = rb_page_size / BALLOON_PAGE_SIZE;
- /*
- * This means the guest has asked to discard some of the 4kiB
- * subpages of a host page, but then changed its mind and
- * asked to keep them after all. It's exceedingly unlikely
- * for a guest to do this in practice, but handle it anyway,
- * since getting it wrong could mean discarding memory the
- * guest is still using. */
- clear_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
- balloon->pbp->bitmap);
-
- if (bitmap_empty(balloon->pbp->bitmap, subpages)) {
- virtio_balloon_reset_pbp(balloon);
- }
+ if (balloon->pbp) {
+ /* Let's play safe and always reset the pbp on deflation requests. */
+ virtio_balloon_reset_pbp(balloon);
}
host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));
--
2.21.0
next prev parent reply other threads:[~2019-07-19 16:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 16:01 [Qemu-devel] [PATCH v1 0/3] virtio-balloon: PartialBalloonedPage rework David Hildenbrand
2019-07-19 16:01 ` David Hildenbrand [this message]
2019-07-22 2:27 ` [Qemu-devel] [PATCH v1 1/3] virtio-balloon: simplify deflate with pbp David Gibson
2019-07-19 16:01 ` [Qemu-devel] [PATCH v1 2/3] virtio-balloon: Better names for offset variables in inflate/deflate code David Hildenbrand
2019-07-22 2:29 ` David Gibson
2019-07-19 16:01 ` [Qemu-devel] [PATCH v1 3/3] virtio-balloon: Rework pbp tracking data David Hildenbrand
2019-07-22 3:04 ` David Gibson
2019-07-22 7:43 ` David Hildenbrand
2019-07-22 8:14 ` Michael S. Tsirkin
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