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ram.c: Do not call save_page_header() from compress threads 

save_page_header() accesses several global variables, so calling it
from multiple threads is pretty ugly.

Instead, call save_page_header() before writing out the compressed
data from the compress buffer to the migration stream.

This also makes the core compress code more independend from ram.c.

Signed-off-by: Lukas Straub <lukasstraub2@web.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Lukas Straub 2023-04-20 11:48:06 +02:00 committed by Juan Quintela
parent b5cf1cd3e8
commit 3e81763e4c
1 changed files with 35 additions and 9 deletions
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44
migration/ram.c
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@ -1465,17 +1465,13 @@ static CompressResult do_compress_ram_page(QEMUFile *f, z_stream *stream,
RAMBlock *block, ram_addr_t offset,
uint8_t *source_buf)
{
RAMState *rs = ram_state;
PageSearchStatus *pss = &rs->pss[RAM_CHANNEL_PRECOPY];
uint8_t *p = block->host + offset;
int ret;
if (save_zero_page_to_file(pss, f, block, offset)) {
if (buffer_is_zero(p, TARGET_PAGE_SIZE)) {
return RES_ZEROPAGE;
}
save_page_header(pss, f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
/*
* copy it to a internal buffer to avoid it being modified by VM
* so that we can catch up the error during compression and
@ -1515,9 +1511,40 @@ static inline void compress_reset_result(CompressParam *param)
param->offset = 0;
}
static int send_queued_data(CompressParam *param)
{
PageSearchStatus *pss = &ram_state->pss[RAM_CHANNEL_PRECOPY];
MigrationState *ms = migrate_get_current();
QEMUFile *file = ms->to_dst_file;
int len = 0;
RAMBlock *block = param->block;
ram_addr_t offset = param->offset;
if (param->result == RES_NONE) {
return 0;
}
assert(block == pss->last_sent_block);
if (param->result == RES_ZEROPAGE) {
len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO);
qemu_put_byte(file, 0);
len += 1;
ram_release_page(block->idstr, offset);
} else if (param->result == RES_COMPRESS) {
len += save_page_header(pss, file, block,
offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
len += qemu_put_qemu_file(file, param->file);
} else {
abort();
}
return len;
}
static void flush_compressed_data(RAMState *rs)
{
MigrationState *ms = migrate_get_current();
int idx, len, thread_count;
if (!save_page_use_compression(rs)) {
@ -1537,7 +1564,7 @@ static void flush_compressed_data(RAMState *rs)
qemu_mutex_lock(&comp_param[idx].mutex);
if (!comp_param[idx].quit) {
CompressParam *param = &comp_param[idx];
len = qemu_put_qemu_file(ms->to_dst_file, param->file);
len = send_queued_data(param);
compress_reset_result(param);
/*
@ -1563,7 +1590,6 @@ static int compress_page_with_multi_thread(RAMBlock *block, ram_addr_t offset)
{
int idx, thread_count, bytes_xmit = -1, pages = -1;
bool wait = migrate_compress_wait_thread();
MigrationState *ms = migrate_get_current();
thread_count = migrate_compress_threads();
qemu_mutex_lock(&comp_done_lock);
@ -1573,7 +1599,7 @@ retry:
CompressParam *param = &comp_param[idx];
qemu_mutex_lock(&param->mutex);
param->done = false;
bytes_xmit = qemu_put_qemu_file(ms->to_dst_file, param->file);
bytes_xmit = send_queued_data(param);
compress_reset_result(param);
set_compress_params(param, block, offset);