From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
Detecting zero page is not a light work, moving it to the thread to
speed the main thread up
Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
---
migration/ram.c | 112 +++++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 78 insertions(+), 34 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 5aa624b3b9..e1909502da 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -351,6 +351,7 @@ CompressionStats compression_counters;
struct CompressParam {
bool done;
bool quit;
+ bool zero_page;
QEMUFile *file;
QemuMutex mutex;
QemuCond cond;
@@ -392,7 +393,7 @@ static QemuThread *decompress_threads;
static QemuMutex decomp_done_lock;
static QemuCond decomp_done_cond;
-static void do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
+static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
ram_addr_t offset, uint8_t *source_buf);
static void *do_data_compress(void *opaque)
@@ -400,6 +401,7 @@ static void *do_data_compress(void *opaque)
CompressParam *param = opaque;
RAMBlock *block;
ram_addr_t offset;
+ bool zero_page;
qemu_mutex_lock(¶m->mutex);
while (!param->quit) {
@@ -409,11 +411,12 @@ static void *do_data_compress(void *opaque)
param->block = NULL;
qemu_mutex_unlock(¶m->mutex);
- do_compress_ram_page(param->file, ¶m->stream, block, offset,
- param->originbuf);
+ zero_page = do_compress_ram_page(param->file, ¶m->stream,
+ block, offset, param->originbuf);
qemu_mutex_lock(&comp_done_lock);
param->done = true;
+ param->zero_page = zero_page;
qemu_cond_signal(&comp_done_cond);
qemu_mutex_unlock(&comp_done_lock);
@@ -1871,13 +1874,19 @@ static int ram_save_multifd_page(RAMState *rs, RAMBlock *block,
return 1;
}
-static void do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
+static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
ram_addr_t offset, uint8_t *source_buf)
{
RAMState *rs = ram_state;
uint8_t *p = block->host + (offset & TARGET_PAGE_MASK);
+ bool zero_page = false;
int ret;
+ if (save_zero_page_to_file(rs, f, block, offset)) {
+ zero_page = true;
+ goto exit;
+ }
+
save_page_header(rs, f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
/*
@@ -1890,10 +1899,12 @@ static void do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
if (ret < 0) {
qemu_file_set_error(migrate_get_current()->to_dst_file, ret);
error_report("compressed data failed!");
- return;
+ return false;
}
+exit:
ram_release_pages(block->idstr, offset & TARGET_PAGE_MASK, 1);
+ return zero_page;
}
static void flush_compressed_data(RAMState *rs)
@@ -1917,10 +1928,20 @@ static void flush_compressed_data(RAMState *rs)
qemu_mutex_lock(&comp_param[idx].mutex);
if (!comp_param[idx].quit) {
len = qemu_put_qemu_file(rs->f, comp_param[idx].file);
- /* 8 means a header with RAM_SAVE_FLAG_CONTINUE. */
- compression_counters.reduced_size += TARGET_PAGE_SIZE - len + 8;
- compression_counters.pages++;
ram_counters.transferred += len;
+
+ /*
+ * it's safe to fetch zero_page without holding comp_done_lock
+ * as there is no further request submitted to the thread,
+ * i.e, the thread should be waiting for a request at this point.
+ */
+ if (comp_param[idx].zero_page) {
+ ram_counters.duplicate++;
+ } else {
+ /* 8 means a header with RAM_SAVE_FLAG_CONTINUE. */
+ compression_counters.reduced_size += TARGET_PAGE_SIZE - len + 8;
+ compression_counters.pages++;
+ }
}
qemu_mutex_unlock(&comp_param[idx].mutex);
}
@@ -1950,12 +1971,16 @@ retry:
set_compress_params(&comp_param[idx], block, offset);
qemu_cond_signal(&comp_param[idx].cond);
qemu_mutex_unlock(&comp_param[idx].mutex);
- pages = 1;
- /* 8 means a header with RAM_SAVE_FLAG_CONTINUE. */
- compression_counters.reduced_size += TARGET_PAGE_SIZE -
- bytes_xmit + 8;
- compression_counters.pages++;
ram_counters.transferred += bytes_xmit;
+ pages = 1;
+ if (comp_param[idx].zero_page) {
+ ram_counters.duplicate++;
+ } else {
+ /* 8 means a header with RAM_SAVE_FLAG_CONTINUE. */
+ compression_counters.reduced_size += TARGET_PAGE_SIZE -
+ bytes_xmit + 8;
+ compression_counters.pages++;
+ }
break;
}
}
@@ -2229,6 +2254,40 @@ static bool save_page_use_compression(RAMState *rs)
return false;
}
+/*
+ * try to compress the page before post it out, return true if the page
+ * has been properly handled by compression, otherwise needs other
+ * paths to handle it
+ */
+static bool save_compress_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
+{
+ if (!save_page_use_compression(rs)) {
+ return false;
+ }
+
+ /*
+ * When starting the process of a new block, the first page of
+ * the block should be sent out before other pages in the same
+ * block, and all the pages in last block should have been sent
+ * out, keeping this order is important, because the 'cont' flag
+ * is used to avoid resending the block name.
+ *
+ * We post the fist page as normal page as compression will take
+ * much CPU resource.
+ */
+ if (block != rs->last_sent_block) {
+ flush_compressed_data(rs);
+ return false;
+ }
+
+ if (compress_page_with_multi_thread(rs, block, offset) > 0) {
+ return true;
+ }
+
+ compression_counters.busy++;
+ return false;
+}
+
/**
* ram_save_target_page: save one target page
*
@@ -2249,15 +2308,8 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
return res;
}
- /*
- * When starting the process of a new block, the first page of
- * the block should be sent out before other pages in the same
- * block, and all the pages in last block should have been sent
- * out, keeping this order is important, because the 'cont' flag
- * is used to avoid resending the block name.
- */
- if (block != rs->last_sent_block && save_page_use_compression(rs)) {
- flush_compressed_data(rs);
+ if (save_compress_page(rs, block, offset)) {
+ return 1;
}
res = save_zero_page(rs, block, offset);
@@ -2275,18 +2327,10 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
}
/*
- * Make sure the first page is sent out before other pages.
- *
- * we post it as normal page as compression will take much
- * CPU resource.
- */
- if (block == rs->last_sent_block && save_page_use_compression(rs)) {
- res = compress_page_with_multi_thread(rs, block, offset);
- if (res > 0) {
- return res;
- }
- compression_counters.busy++;
- } else if (migrate_use_multifd()) {
+ * do not use multifd for compression as the first page in the new
+ * block should be posted out before sending the compressed page
+ */
+ if (!save_page_use_compression(rs) && migrate_use_multifd()) {
return ram_save_multifd_page(rs, block, offset);
}
--
2.14.4
