find_ram_offset optimization
The ram_offset allocator searches the smalest gap in the ram_offset address space. This is slow especialy in combination with many allocation (i.e. snapshots). When it is known that there is no gap, this is now optimized.
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@ -41,6 +41,7 @@ typedef struct {
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// This struct is originally from qemu/include/exec/ramlist.h
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typedef struct RAMList {
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bool freed;
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RAMBlock *mru_block;
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QLIST_HEAD(, RAMBlock) blocks;
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} RAMList;
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20
qemu/exec.c
20
qemu/exec.c
@ -955,6 +955,21 @@ void flatview_add_to_dispatch(struct uc_struct *uc, FlatView *fv, MemoryRegionSe
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register_subpage(uc, fv, &remain);
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}
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static ram_addr_t find_ram_offset_last(struct uc_struct *uc, ram_addr_t size)
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{
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RAMBlock *block;
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ram_addr_t result = 0;
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RAMBLOCK_FOREACH(block) {
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result = MAX(block->offset + block->max_length, result);
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}
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if (result + size > RAM_ADDR_MAX) {
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abort();
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}
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return result;
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}
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/* Allocate space within the ram_addr_t space that governs the
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* dirty bitmaps.
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* Called with the ramlist lock held.
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@ -970,6 +985,10 @@ static ram_addr_t find_ram_offset(struct uc_struct *uc, ram_addr_t size)
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return 0;
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}
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if (!uc->ram_list.freed) {
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return find_ram_offset_last(uc, size);
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}
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RAMBLOCK_FOREACH(block) {
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ram_addr_t candidate, next = RAM_ADDR_MAX;
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@ -1145,6 +1164,7 @@ void qemu_ram_free(struct uc_struct *uc, RAMBlock *block)
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QLIST_REMOVE_RCU(block, next);
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uc->ram_list.mru_block = NULL;
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uc->ram_list.freed = true;
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/* Write list before version */
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//smp_wmb();
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// call_rcu(block, reclaim_ramblock, rcu);
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