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authorDr. David Alan Gilbert <dgilbert@redhat.com>2018-01-05 17:01:37 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2018-01-16 14:54:52 +0100
commit154cc9ea3bc840199714ee7b95277c572c5d1533 (patch)
tree01955a02d4407a288cc9389bdd0bd2d53b9ec663 /exec.c
parentaa777e297c8408ee5bebc4f6a2e00071224e4a64 (diff)
find_ram_offset: Add comments and tracing
Add some comments so I can understand the various nested loops. Add some tracing so I can see what they're doing. Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Message-Id: <20180105170138.23357-2-dgilbert@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'exec.c')
-rw-r--r--exec.c29
1 files changed, 22 insertions, 7 deletions
diff --git a/exec.c b/exec.c
index 4722e521d4..5e2fb55080 100644
--- a/exec.c
+++ b/exec.c
@@ -1660,7 +1660,10 @@ static void *file_ram_alloc(RAMBlock *block,
}
#endif
-/* Called with the ramlist lock held. */
+/* Allocate space within the ram_addr_t space that governs the
+ * dirty bitmaps.
+ * Called with the ramlist lock held.
+ */
static ram_addr_t find_ram_offset(ram_addr_t size)
{
RAMBlock *block, *next_block;
@@ -1673,19 +1676,29 @@ static ram_addr_t find_ram_offset(ram_addr_t size)
}
RAMBLOCK_FOREACH(block) {
- ram_addr_t end, next = RAM_ADDR_MAX;
+ ram_addr_t candidate, next = RAM_ADDR_MAX;
- end = block->offset + block->max_length;
+ candidate = block->offset + block->max_length;
+ /* Search for the closest following block
+ * and find the gap.
+ */
RAMBLOCK_FOREACH(next_block) {
- if (next_block->offset >= end) {
+ if (next_block->offset >= candidate) {
next = MIN(next, next_block->offset);
}
}
- if (next - end >= size && next - end < mingap) {
- offset = end;
- mingap = next - end;
+
+ /* If it fits remember our place and remember the size
+ * of gap, but keep going so that we might find a smaller
+ * gap to fill so avoiding fragmentation.
+ */
+ if (next - candidate >= size && next - candidate < mingap) {
+ offset = candidate;
+ mingap = next - candidate;
}
+
+ trace_find_ram_offset_loop(size, candidate, offset, next, mingap);
}
if (offset == RAM_ADDR_MAX) {
@@ -1694,6 +1707,8 @@ static ram_addr_t find_ram_offset(ram_addr_t size)
abort();
}
+ trace_find_ram_offset(size, offset);
+
return offset;
}