* Wei Yang (richardw.y...@linux.intel.com) wrote:
> In postcopy-ram.c, we provide three functions to discard certain
> RAMBlock range:
>
> * postcopy_discard_send_init()
> * postcopy_discard_send_range()
> * postcopy_discard_send_finish()
>
> Currently, we allocate/deallocate PostcopyDiscardState for each RAMBlock
> on sending discard information to destination. This is not necessary and
> the same data area could be reused for each RAMBlock.
>
> This patch defines PostcopyDiscardState a static variable. By doing so:
>
> 1) avoid memory allocation and deallocation to the system
> 2) avoid potential failure of memory allocation
> 3) hide some details for their users
>
> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> v2:
> * make it a static variable, suggested by Dave
> ---
> migration/postcopy-ram.c | 70 +++++++++++++++++-----------------------
> migration/postcopy-ram.h | 13 +++-----
> migration/ram.c | 30 +++++++----------
> 3 files changed, 46 insertions(+), 67 deletions(-)
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 7b3e198538..cf2400b47e 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -1375,22 +1375,16 @@ void
> postcopy_fault_thread_notify(MigrationIncomingState *mis)
> * asking to discard individual ranges.
> *
> * @ms: The current migration state.
> - * @offset: the bitmap offset of the named RAMBlock in the migration
> - * bitmap.
> + * @offset: the bitmap offset of the named RAMBlock in the migration bitmap.
> * @name: RAMBlock that discards will operate on.
> - *
> - * returns: a new PDS.
> */
> -PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
> - const char *name)
> +static PostcopyDiscardState pds = {0};
> +void postcopy_discard_send_init(MigrationState *ms, const char *name)
> {
> - PostcopyDiscardState *res = g_malloc0(sizeof(PostcopyDiscardState));
> -
> - if (res) {
> - res->ramblock_name = name;
> - }
> -
> - return res;
> + pds.ramblock_name = name;
> + pds.cur_entry = 0;
> + pds.nsentwords = 0;
> + pds.nsentcmds = 0;
> }
>
> /**
> @@ -1399,30 +1393,29 @@ PostcopyDiscardState
> *postcopy_discard_send_init(MigrationState *ms,
> * be sent later.
> *
> * @ms: Current migration state.
> - * @pds: Structure initialised by postcopy_discard_send_init().
> * @start,@length: a range of pages in the migration bitmap in the
> * RAM block passed to postcopy_discard_send_init() (length=1 is one page)
> */
> -void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState
> *pds,
> - unsigned long start, unsigned long length)
> +void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
> + unsigned long length)
> {
> size_t tp_size = qemu_target_page_size();
> /* Convert to byte offsets within the RAM block */
> - pds->start_list[pds->cur_entry] = start * tp_size;
> - pds->length_list[pds->cur_entry] = length * tp_size;
> - trace_postcopy_discard_send_range(pds->ramblock_name, start, length);
> - pds->cur_entry++;
> - pds->nsentwords++;
> + pds.start_list[pds.cur_entry] = start * tp_size;
> + pds.length_list[pds.cur_entry] = length * tp_size;
> + trace_postcopy_discard_send_range(pds.ramblock_name, start, length);
> + pds.cur_entry++;
> + pds.nsentwords++;
>
> - if (pds->cur_entry == MAX_DISCARDS_PER_COMMAND) {
> + if (pds.cur_entry == MAX_DISCARDS_PER_COMMAND) {
> /* Full set, ship it! */
> qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
> - pds->ramblock_name,
> - pds->cur_entry,
> - pds->start_list,
> - pds->length_list);
> - pds->nsentcmds++;
> - pds->cur_entry = 0;
> + pds.ramblock_name,
> + pds.cur_entry,
> + pds.start_list,
> + pds.length_list);
> + pds.nsentcmds++;
> + pds.cur_entry = 0;
> }
> }
>
> @@ -1431,24 +1424,21 @@ void postcopy_discard_send_range(MigrationState *ms,
> PostcopyDiscardState *pds,
> * bitmap code. Sends any outstanding discard messages, frees the PDS
> *
> * @ms: Current migration state.
> - * @pds: Structure initialised by postcopy_discard_send_init().
> */
> -void postcopy_discard_send_finish(MigrationState *ms, PostcopyDiscardState
> *pds)
> +void postcopy_discard_send_finish(MigrationState *ms)
> {
> /* Anything unsent? */
> - if (pds->cur_entry) {
> + if (pds.cur_entry) {
> qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
> - pds->ramblock_name,
> - pds->cur_entry,
> - pds->start_list,
> - pds->length_list);
> - pds->nsentcmds++;
> + pds.ramblock_name,
> + pds.cur_entry,
> + pds.start_list,
> + pds.length_list);
> + pds.nsentcmds++;
> }
>
> - trace_postcopy_discard_send_finish(pds->ramblock_name, pds->nsentwords,
> - pds->nsentcmds);
> -
> - g_free(pds);
> + trace_postcopy_discard_send_finish(pds.ramblock_name, pds.nsentwords,
> + pds.nsentcmds);
> }
>
> /*
> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> index e3a5cfd2d8..e3dde32155 100644
> --- a/migration/postcopy-ram.h
> +++ b/migration/postcopy-ram.h
> @@ -43,10 +43,8 @@ int postcopy_ram_prepare_discard(MigrationIncomingState
> *mis);
>
> /*
> * Called at the start of each RAMBlock by the bitmap code.
> - * Returns a new PDS
> */
> -PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
> - const char *name);
> +void postcopy_discard_send_init(MigrationState *ms, const char *name);
>
> /*
> * Called by the bitmap code for each chunk to discard.
> @@ -55,15 +53,14 @@ PostcopyDiscardState
> *postcopy_discard_send_init(MigrationState *ms,
> * @start,@length: a range of pages in the migration bitmap in the
> * RAM block passed to postcopy_discard_send_init() (length=1 is one page)
> */
> -void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState
> *pds,
> - unsigned long start, unsigned long length);
> +void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
> + unsigned long length);
>
> /*
> * Called at the end of each RAMBlock by the bitmap code.
> - * Sends any outstanding discard messages, frees the PDS.
> + * Sends any outstanding discard messages.
> */
> -void postcopy_discard_send_finish(MigrationState *ms,
> - PostcopyDiscardState *pds);
> +void postcopy_discard_send_finish(MigrationState *ms);
>
> /*
> * Place a page (from) at (host) efficiently
> diff --git a/migration/ram.c b/migration/ram.c
> index ecd10baa43..7b7155a368 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2761,12 +2761,9 @@ void
> ram_postcopy_migrated_memory_release(MigrationState *ms)
> * with the dirtymap; so a '1' means it's either dirty or unsent.
> *
> * @ms: current migration state
> - * @pds: state for postcopy
> * @block: RAMBlock to discard
> */
> -static int postcopy_send_discard_bm_ram(MigrationState *ms,
> - PostcopyDiscardState *pds,
> - RAMBlock *block)
> +static int postcopy_send_discard_bm_ram(MigrationState *ms, RAMBlock *block)
> {
> unsigned long end = block->used_length >> TARGET_PAGE_BITS;
> unsigned long current;
> @@ -2787,7 +2784,7 @@ static int postcopy_send_discard_bm_ram(MigrationState
> *ms,
> } else {
> discard_length = zero - one;
> }
> - postcopy_discard_send_range(ms, pds, one, discard_length);
> + postcopy_discard_send_range(ms, one, discard_length);
> current = one + discard_length;
> }
>
> @@ -2813,16 +2810,15 @@ static int
> postcopy_each_ram_send_discard(MigrationState *ms)
> int ret;
>
> RAMBLOCK_FOREACH_NOT_IGNORED(block) {
> - PostcopyDiscardState *pds =
> - postcopy_discard_send_init(ms, block->idstr);
> + postcopy_discard_send_init(ms, block->idstr);
>
> /*
> * Postcopy sends chunks of bitmap over the wire, but it
> * just needs indexes at this point, avoids it having
> * target page specific code.
> */
> - ret = postcopy_send_discard_bm_ram(ms, pds, block);
> - postcopy_discard_send_finish(ms, pds);
> + ret = postcopy_send_discard_bm_ram(ms, block);
> + postcopy_discard_send_finish(ms);
> if (ret) {
> return ret;
> }
> @@ -2845,11 +2841,9 @@ static int
> postcopy_each_ram_send_discard(MigrationState *ms)
> * @unsent_pass: if true we need to canonicalize partially unsent host pages
> * otherwise we need to canonicalize partially dirty host pages
> * @block: block that contains the page we want to canonicalize
> - * @pds: state for postcopy
> */
> static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool
> unsent_pass,
> - RAMBlock *block,
> - PostcopyDiscardState *pds)
> + RAMBlock *block)
> {
> RAMState *rs = ram_state;
> unsigned long *bitmap = block->bmap;
> @@ -2910,8 +2904,7 @@ static void
> postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
> * (any partially sent pages were already discarded
> * by the previous unsent_pass)
> */
> - postcopy_discard_send_range(ms, pds, fixup_start_addr,
> - host_ratio);
> + postcopy_discard_send_range(ms, fixup_start_addr,
> host_ratio);
> }
>
> /* Clean up the bitmap */
> @@ -2954,18 +2947,17 @@ static void
> postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
> */
> static int postcopy_chunk_hostpages(MigrationState *ms, RAMBlock *block)
> {
> - PostcopyDiscardState *pds =
> - postcopy_discard_send_init(ms, block->idstr);
> + postcopy_discard_send_init(ms, block->idstr);
>
> /* First pass: Discard all partially sent host pages */
> - postcopy_chunk_hostpages_pass(ms, true, block, pds);
> + postcopy_chunk_hostpages_pass(ms, true, block);
> /*
> * Second pass: Ensure that all partially dirty host pages are made
> * fully dirty.
> */
> - postcopy_chunk_hostpages_pass(ms, false, block, pds);
> + postcopy_chunk_hostpages_pass(ms, false, block);
>
> - postcopy_discard_send_finish(ms, pds);
> + postcopy_discard_send_finish(ms);
> return 0;
> }
>
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
