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exec: avoid unnecessary cacheline bounce on ram_list.mru_block

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Whenever the MRU cache hits for the list of RAM blocks, qemu_get_ram_block
does an unnecessary write that causes a processor cache line to bounce
from one core to another.  This causes a performance hit.

Reported-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Paolo Bonzini 2015-10-22 13:51:30 +02:00 committed by Michael Tokarev
parent 74de807f79
commit 68851b98e5
1 changed files with 1 additions and 1 deletions
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2
exec.c
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@ -903,7 +903,7 @@ static RAMBlock *qemu_get_ram_block(ram_addr_t addr)
block = atomic_rcu_read(&ram_list.mru_block); block = atomic_rcu_read(&ram_list.mru_block);
if (block && addr - block->offset < block->max_length) { if (block && addr - block->offset < block->max_length) {
goto found; return block;
} }
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) { QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
if (addr - block->offset < block->max_length) { if (addr - block->offset < block->max_length) {