* Wei Yang (richardw.y...@linux.intel.com) wrote:
> This patch enable compress with postcopy.
>
> This is a RFC and based on some unmerged patch
>
> "migration: extract ram_load_precopy"
> "migration/postcopy: skip compression when postcopy is active"
>
> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
> ---
> migration/postcopy-ram.c | 3 +--
> migration/ram.c | 35 +++++++++++++++++++++--------------
> 2 files changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index a7e7ec9c22..70b6beb5a9 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -1252,8 +1252,7 @@ int postcopy_place_page_zero(MigrationIncomingState
> *mis, void *host,
> }
> memset(mis->postcopy_tmp_zero_page, '\0',
> mis->largest_page_size);
> }
> - return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
> - rb);
> + return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
> rb);
Please keep these type of cleanups separate.
> }
> }
>
> diff --git a/migration/ram.c b/migration/ram.c
> index a0d3bc60b2..c1d6eadf38 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2384,16 +2384,6 @@ static bool save_page_use_compression(RAMState *rs)
> return false;
> }
>
> - /*
> - * The decompression threads asynchronously write into RAM
> - * rather than use the atomic copies needed to avoid
> - * userfaulting. It should be possible to fix the decompression
> - * threads for compatibility in future.
> - */
> - if (migration_in_postcopy()) {
> - return false;
> - }
> -
> /*
> * If xbzrle is on, stop using the data compression after first
> * round of migration even if compression is enabled. In theory,
> @@ -3433,6 +3423,11 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
> }
> i++;
> }
> +
> + if (migrate_postcopy_ram()) {
> + flush_compressed_data(rs);
> + }
> +
> rcu_read_unlock();
>
> /*
> @@ -4019,6 +4014,7 @@ static int ram_load_postcopy(QEMUFile *f)
> void *place_source = NULL;
> RAMBlock *block = NULL;
> uint8_t ch;
> + int len;
>
> addr = qemu_get_be64(f);
>
> @@ -4036,7 +4032,8 @@ static int ram_load_postcopy(QEMUFile *f)
>
> trace_ram_load_postcopy_loop((uint64_t)addr, flags);
> place_needed = false;
> - if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE)) {
> + if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE |
> + RAM_SAVE_FLAG_COMPRESS_PAGE)) {
> block = ram_block_from_stream(f, flags);
>
> host = host_from_ram_block_offset(block, addr);
> @@ -4109,6 +4106,17 @@ static int ram_load_postcopy(QEMUFile *f)
> TARGET_PAGE_SIZE);
> }
> break;
> + case RAM_SAVE_FLAG_COMPRESS_PAGE:
> + all_zero = false;
> + len = qemu_get_be32(f);
> + if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) {
> + error_report("Invalid compressed data length: %d", len);
> + ret = -EINVAL;
> + break;
> + }
> + decompress_data_with_multi_threads(f, page_buffer, len);
> + ret |= wait_for_decompress_done();
I think this might work for a 4k page host; but I'm not sure it's
safe on hugepages or ARM/Power where they have bigger pages.
ram_load_postcopy relies on all of the pages within a single hostpage
arriving before the last subpage and that's what then triggers the call
to postcopy_place_page; that relies on some ordering - but I don't
think that the multiple compress threads on the source have any ordering
between the threads - or am I missing something about how the multiple
threads are organised?
Dave
> + break;
> case RAM_SAVE_FLAG_EOS:
> /* normal exit */
> multifd_recv_sync_main();
> @@ -4130,8 +4138,7 @@ static int ram_load_postcopy(QEMUFile *f)
> void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
>
> if (all_zero) {
> - ret = postcopy_place_page_zero(mis, place_dest,
> - block);
> + ret = postcopy_place_page_zero(mis, place_dest, block);
> } else {
> ret = postcopy_place_page(mis, place_dest,
> place_source, block);
> @@ -4372,6 +4379,7 @@ static int ram_load_precopy(QEMUFile *f)
> }
> }
>
> + ret |= wait_for_decompress_done();
> return ret;
> }
>
> @@ -4405,7 +4413,6 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> ret = ram_load_precopy(f);
> }
>
> - ret |= wait_for_decompress_done();
> rcu_read_unlock();
> trace_ram_load_complete(ret, seq_iter);
>
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
