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[Qemu-devel] [PATCH 29/35] ram: optimize migration bitmap walking
From: |
Juan Quintela |
Subject: |
[Qemu-devel] [PATCH 29/35] ram: optimize migration bitmap walking |
Date: |
Tue, 11 Dec 2012 13:47:05 +0100 |
Instead of testing each page individually, we search what is the next
dirty page with a bitmap operation. We have to reorganize the code to
move from a "for" loop, to a while(dirty) loop.
Signed-off-by: Juan Quintela <address@hidden>
---
arch_init.c | 45 ++++++++++++++++++++++++++-------------------
1 file changed, 26 insertions(+), 19 deletions(-)
diff --git a/arch_init.c b/arch_init.c
index b204602..6c12a7d 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -343,18 +343,21 @@ static unsigned long *migration_bitmap;
static uint64_t migration_dirty_pages;
static uint32_t last_version;
-static inline bool migration_bitmap_test_and_reset_dirty(MemoryRegion *mr,
- ram_addr_t offset)
+static inline
+ram_addr_t migration_bitmap_find_and_reset_dirty(MemoryRegion *mr,
+ ram_addr_t start)
{
- bool ret;
- int nr = (mr->ram_addr + offset) >> TARGET_PAGE_BITS;
+ unsigned long base = mr->ram_addr >> TARGET_PAGE_BITS;
+ unsigned long nr = base + (start >> TARGET_PAGE_BITS);
+ unsigned long size = base + (int128_get64(mr->size) >> TARGET_PAGE_BITS);
- ret = test_and_clear_bit(nr, migration_bitmap);
+ unsigned long next = find_next_bit(migration_bitmap, size, nr);
- if (ret) {
+ if (next < size) {
+ clear_bit(next, migration_bitmap);
migration_dirty_pages--;
}
- return ret;
+ return (next - base) << TARGET_PAGE_BITS;
}
static inline bool migration_bitmap_set_dirty(MemoryRegion *mr,
@@ -423,6 +426,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
{
RAMBlock *block = last_seen_block;
ram_addr_t offset = last_offset;
+ bool complete_round = false;
int bytes_sent = -1;
MemoryRegion *mr;
ram_addr_t current_addr;
@@ -430,9 +434,21 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
if (!block)
block = QLIST_FIRST(&ram_list.blocks);
- do {
+ while(true) {
mr = block->mr;
- if (migration_bitmap_test_and_reset_dirty(mr, offset)) {
+ offset = migration_bitmap_find_and_reset_dirty(mr, offset);
+ if (complete_round && block == last_seen_block &&
+ offset >= last_offset) {
+ break;
+ }
+ if (offset >= block->length) {
+ offset = 0;
+ block = QLIST_NEXT(block, next);
+ if (!block) {
+ block = QLIST_FIRST(&ram_list.blocks);
+ complete_round = true;
+ }
+ } else {
uint8_t *p;
int cont = (block == last_sent_block) ?
RAM_SAVE_FLAG_CONTINUE : 0;
@@ -467,16 +483,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
break;
}
}
-
- offset += TARGET_PAGE_SIZE;
- if (offset >= block->length) {
- offset = 0;
- block = QLIST_NEXT(block, next);
- if (!block)
- block = QLIST_FIRST(&ram_list.blocks);
- }
- } while (block != last_seen_block || offset != last_offset);
-
+ }
last_seen_block = block;
last_offset = offset;
--
1.7.11.7
- [Qemu-devel] [PATCH 20/35] migration: move begining stage to the migration thread, (continued)
- [Qemu-devel] [PATCH 20/35] migration: move begining stage to the migration thread, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 19/35] migration: move migration notifier, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 25/35] ram: Add last_sent_block, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 21/35] migration: Add buffered_flush error handling, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 27/35] ram: Use memory_region_test_and_clear_dirty, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 26/35] memory: introduce memory_region_test_and_clear_dirty, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 24/35] ram: rename last_block to last_seen_block, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 35/35] migration: print times for end phase, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 32/35] ram: add free_space parameter to save_live functions, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 30/35] ram: account the amount of transferred ram better, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 29/35] ram: optimize migration bitmap walking,
Juan Quintela <=
- [Qemu-devel] [PATCH 31/35] ram: refactor ram_save_block() return value, Juan Quintela, 2012/12/11
- [Qemu-devel] [PATCH 34/35] ram: reuse ram_save_iterate() for the complete stage, Juan Quintela, 2012/12/11
- Re: [Qemu-devel] [PATCH 00/35] Migration thread (20121211), Paolo Bonzini, 2012/12/11
- [Qemu-devel] [PATCH 33/35] ram: remove xbrle last_stage optimization, Juan Quintela, 2012/12/11