From: Juan Quintela <quintela@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Eduardo Habkost" <ehabkost@redhat.com>,
kvm@vger.kernel.org, "David Hildenbrand" <david@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Paul Durrant" <paul@xen.org>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Markus Armbruster" <armbru@redhat.com>,
"Peter Xu" <peterx@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Juan Quintela" <quintela@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Anthony Perard" <anthony.perard@citrix.com>,
xen-devel@lists.xenproject.org, "Eric Blake" <eblake@redhat.com>
Subject: [PULL 17/20] migration/ram: Factor out populating pages readable in ram_block_populate_pages()
Date: Mon, 1 Nov 2021 23:09:09 +0100 [thread overview]
Message-ID: <20211101220912.10039-18-quintela@redhat.com> (raw)
In-Reply-To: <20211101220912.10039-1-quintela@redhat.com>
From: David Hildenbrand <david@redhat.com>
Let's factor out prefaulting/populating to make further changes easier to
review and add a comment what we are actually expecting to happen. While at
it, use the actual page size of the ramblock, which defaults to
qemu_real_host_page_size for anonymous memory. Further, rename
ram_block_populate_pages() to ram_block_populate_read() as well, to make
it clearer what we are doing.
In the future, we might want to use MADV_POPULATE_READ to speed up
population.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
migration/ram.c | 35 ++++++++++++++++++++++-------------
1 file changed, 22 insertions(+), 13 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 54df5dc0fc..92c7b788ae 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1639,26 +1639,35 @@ out:
return ret;
}
+static inline void populate_read_range(RAMBlock *block, ram_addr_t offset,
+ ram_addr_t size)
+{
+ /*
+ * We read one byte of each page; this will preallocate page tables if
+ * required and populate the shared zeropage on MAP_PRIVATE anonymous memory
+ * where no page was populated yet. This might require adaption when
+ * supporting other mappings, like shmem.
+ */
+ for (; offset < size; offset += block->page_size) {
+ char tmp = *((char *)block->host + offset);
+
+ /* Don't optimize the read out */
+ asm volatile("" : "+r" (tmp));
+ }
+}
+
/*
- * ram_block_populate_pages: populate memory in the RAM block by reading
- * an integer from the beginning of each page.
+ * ram_block_populate_read: preallocate page tables and populate pages in the
+ * RAM block by reading a byte of each page.
*
* Since it's solely used for userfault_fd WP feature, here we just
* hardcode page size to qemu_real_host_page_size.
*
* @block: RAM block to populate
*/
-static void ram_block_populate_pages(RAMBlock *block)
+static void ram_block_populate_read(RAMBlock *block)
{
- char *ptr = (char *) block->host;
-
- for (ram_addr_t offset = 0; offset < block->used_length;
- offset += qemu_real_host_page_size) {
- char tmp = *(ptr + offset);
-
- /* Don't optimize the read out */
- asm volatile("" : "+r" (tmp));
- }
+ populate_read_range(block, 0, block->used_length);
}
/*
@@ -1684,7 +1693,7 @@ void ram_write_tracking_prepare(void)
* UFFDIO_WRITEPROTECT_MODE_WP mode setting would silently skip
* pages with pte_none() entries in page table.
*/
- ram_block_populate_pages(block);
+ ram_block_populate_read(block);
}
}
--
2.33.1
next prev parent reply other threads:[~2021-11-01 22:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 22:08 [PULL 00/20] Migration 20211031 patches Juan Quintela
2021-11-01 22:08 ` [PULL 01/20] migration/rdma: Fix out of order wrid Juan Quintela
2021-11-01 22:08 ` [PULL 02/20] KVM: introduce dirty_pages and kvm_dirty_ring_enabled Juan Quintela
2021-11-01 22:08 ` [PULL 03/20] memory: make global_dirty_tracking a bitmask Juan Quintela
2021-11-01 22:08 ` [PULL 04/20] migration/dirtyrate: introduce struct and adjust DirtyRateStat Juan Quintela
2021-11-04 20:54 ` Eric Blake
2021-11-01 22:08 ` [PULL 05/20] migration/dirtyrate: adjust order of registering thread Juan Quintela
2021-11-01 22:08 ` [PULL 06/20] migration/dirtyrate: move init step of calculation to main thread Juan Quintela
2021-11-01 22:08 ` [PULL 07/20] migration/dirtyrate: implement dirty-ring dirtyrate calculation Juan Quintela
2021-11-04 22:05 ` Philippe Mathieu-Daudé
2021-11-06 11:45 ` Juan Quintela
2021-11-01 22:09 ` [PULL 08/20] migration: Make migration blocker work for snapshots too Juan Quintela
2021-11-01 22:09 ` [PULL 09/20] migration: Add migrate_add_blocker_internal() Juan Quintela
2021-11-01 22:09 ` [PULL 10/20] dump-guest-memory: Block live migration Juan Quintela
2021-11-01 22:09 ` [PULL 11/20] memory: Introduce replay_discarded callback for RamDiscardManager Juan Quintela
2021-11-01 22:09 ` [PULL 12/20] virtio-mem: Implement replay_discarded RamDiscardManager callback Juan Quintela
2021-11-01 22:09 ` [PULL 13/20] migration/ram: Handle RAMBlocks with a RamDiscardManager on the migration source Juan Quintela
2021-11-01 22:09 ` [PULL 14/20] virtio-mem: Drop precopy notifier Juan Quintela
2021-11-01 22:09 ` [PULL 15/20] migration/postcopy: Handle RAMBlocks with a RamDiscardManager on the destination Juan Quintela
2021-11-01 22:09 ` [PULL 16/20] migration: Simplify alignment and alignment checks Juan Quintela
2021-11-01 22:09 ` Juan Quintela [this message]
2021-11-01 22:09 ` [PULL 18/20] migration/ram: Handle RAMBlocks with a RamDiscardManager on background snapshots Juan Quintela
2021-11-01 22:09 ` [PULL 19/20] memory: introduce total_dirty_pages to stat dirty pages Juan Quintela
2021-11-01 22:09 ` [PULL 20/20] migration/dirtyrate: implement dirty-bitmap dirtyrate calculation Juan Quintela
2021-11-02 15:45 ` [PULL 00/20] Migration 20211031 patches Richard Henderson
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