* Wei Yang (richardw.y...@linux.intel.com) wrote:
> postcopy requires to place a whole host page, while migration thread
> migrate memory in target page size. This makes postcopy need to collect
> all target pages in one host page before placing via userfaultfd.
>
> To enable compress during postcopy, there are two problems to solve:
>
> 1. Random order for target page arrival
> 2. Target pages in one host page arrives without interrupt by target
> page from other host page
>
> The first one is handled by previous cleanup patch.
>
> This patch handles the second one by:
>
> 1. Flush compress thread for each host page
> 2. Wait for decompress thread for before placing host page
>
> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
> ---
> migration/migration.c | 11 -----------
> migration/ram.c | 28 +++++++++++++++++++++++++++-
> 2 files changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 3febd0f8f3..72e53e2249 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1000,17 +1000,6 @@ static bool migrate_caps_check(bool *cap_list,
> #endif
>
> if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) {
> - if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) {
> - /* 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.
> - */
> - error_setg(errp, "Postcopy is not currently compatible "
> - "with compression");
> - return false;
> - }
> -
Yes, I think that's safe - as long as the 'compress' gets set on both
sides you should never get a combination of one side trying it and the
other not being capable.
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> /* This check is reasonably expensive, so only when it's being
> * set the first time, also it's only the destination that needs
> * special support.
> diff --git a/migration/ram.c b/migration/ram.c
> index da0596411c..1403978d75 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3449,6 +3449,14 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
>
> rs->target_page_count += pages;
>
> + /*
> + * During postcopy, it is necessary to make sure one whole host
> + * page is sent in one chunk.
> + */
> + if (migrate_postcopy_ram()) {
> + flush_compressed_data(rs);
> + }
> +
> /*
> * we want to check in the 1st loop, just in case it was the 1st
> * time and we had to sync the dirty bitmap.
> @@ -4025,6 +4033,7 @@ static int ram_load_postcopy(QEMUFile *f)
> void *place_source = NULL;
> RAMBlock *block = NULL;
> uint8_t ch;
> + int len;
>
> addr = qemu_get_be64(f);
>
> @@ -4042,7 +4051,8 @@ 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);
> @@ -4114,6 +4124,17 @@ 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);
> + break;
> +
> case RAM_SAVE_FLAG_EOS:
> /* normal exit */
> multifd_recv_sync_main();
> @@ -4125,6 +4146,11 @@ static int ram_load_postcopy(QEMUFile *f)
> break;
> }
>
> + /* Got the whole host page, wait for decompress before placing. */
> + if (place_needed) {
> + ret |= wait_for_decompress_done();
> + }
> +
> /* Detect for any possible file errors */
> if (!ret && qemu_file_get_error(f)) {
> ret = qemu_file_get_error(f);
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
