From 27af7d6ea5015e5ef1f7985eab94a8a218267a2b Mon Sep 17 00:00:00 2001 From: ChenLiang Date: Mon, 24 Nov 2014 19:55:47 +0800 Subject: xbzrle: optimize XBZRLE to decrease the cache misses Avoid hot pages being replaced by others to remarkably decrease cache misses Sample results with the test program which quote from xbzrle.txt ran in vm:(migrate bandwidth:1GE and xbzrle cache size 8MB) the test program: include include int main() { char *buf = (char *) calloc(4096, 4096); while (1) { int i; for (i = 0; i < 4096 * 4; i++) { buf[i * 4096 / 4]++; } printf("."); } } before this patch: virsh qemu-monitor-command test_vm '{"execute": "query-migrate"}' {"return":{"expected-downtime":1020,"xbzrle-cache":{"bytes":1108284, "cache-size":8388608,"cache-miss-rate":0.987013,"pages":18297,"overflow":8, "cache-miss":1228737},"status":"active","setup-time":10,"total-time":52398, "ram":{"total":12466991104,"remaining":1695744,"mbps":935.559472, "transferred":5780760580,"dirty-sync-counter":271,"duplicate":2878530, "dirty-pages-rate":29130,"skipped":0,"normal-bytes":5748592640, "normal":1403465}},"id":"libvirt-706"} 18k pages sent compressed in 52 seconds. cache-miss-rate is 98.7%, totally miss. after optimizing: virsh qemu-monitor-command test_vm '{"execute": "query-migrate"}' {"return":{"expected-downtime":2054,"xbzrle-cache":{"bytes":5066763, "cache-size":8388608,"cache-miss-rate":0.485924,"pages":194823,"overflow":0, "cache-miss":210653},"status":"active","setup-time":11,"total-time":18729, "ram":{"total":12466991104,"remaining":3895296,"mbps":937.663549, "transferred":1615042219,"dirty-sync-counter":98,"duplicate":2869840, "dirty-pages-rate":58781,"skipped":0,"normal-bytes":1588404224, "normal":387794}},"id":"libvirt-266"} 194k pages sent compressed in 18 seconds. The value of cache-miss-rate decrease to 48.59%. Signed-off-by: ChenLiang Signed-off-by: Gonglei Reviewed-by: Eric Blake Signed-off-by: Amit Shah --- arch_init.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'arch_init.c') diff --git a/arch_init.c b/arch_init.c index cfedbf08af..89c8fa46bb 100644 --- a/arch_init.c +++ b/arch_init.c @@ -346,7 +346,8 @@ static void xbzrle_cache_zero_page(ram_addr_t current_addr) /* We don't care if this fails to allocate a new cache page * as long as it updated an old one */ - cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE); + cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE, + bitmap_sync_count); } #define ENCODING_FLAG_XBZRLE 0x1 @@ -358,10 +359,11 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, int encoded_len = 0, bytes_sent = -1; uint8_t *prev_cached_page; - if (!cache_is_cached(XBZRLE.cache, current_addr)) { + if (!cache_is_cached(XBZRLE.cache, current_addr, bitmap_sync_count)) { acct_info.xbzrle_cache_miss++; if (!last_stage) { - if (cache_insert(XBZRLE.cache, current_addr, *current_data) == -1) { + if (cache_insert(XBZRLE.cache, current_addr, *current_data, + bitmap_sync_count) == -1) { return -1; } else { /* update *current_data when the page has been -- cgit v1.2.1