On Fri, Feb 16, 2018 at 01:16:13PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Send requests back to the source for shared page requests.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/migration.h | 2 ++
> migration/postcopy-ram.c | 31 ++++++++++++++++++++++++++++---
> migration/postcopy-ram.h | 3 +++
> migration/trace-events | 2 ++
> 4 files changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/migration/migration.h b/migration/migration.h
> index d158e62cf2..457bf37ec2 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -46,6 +46,8 @@ struct MigrationIncomingState {
> int userfault_quit_fd;
> QEMUFile *to_src_file;
> QemuMutex rp_mutex; /* We send replies from multiple threads */
> + /* RAMBlock of last request sent to source */
> + RAMBlock *last_rb;
> void *postcopy_tmp_page;
> void *postcopy_tmp_zero_page;
> /* PostCopyFD's for external userfaultfds & handlers of shared memory */
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index d118b78bf5..277ff749a0 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -534,6 +534,31 @@ static int ram_block_enable_notify(const char
> *block_name, void *host_addr,
> return 0;
> }
>
> +/*
> + * Callback from shared fault handlers to ask for a page,
> + * the page must be specified by a RAMBlock and an offset in that rb
> + */
> +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
> + uint64_t client_addr, uint64_t rb_offset)
> +{
> + size_t pagesize = qemu_ram_pagesize(rb);
> + uint64_t aligned_rbo = rb_offset & ~(pagesize - 1);
> + MigrationIncomingState *mis = migration_incoming_get_current();
> +
> + trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb),
> + rb_offset);
> + /* TODO: Check bitmap to see if we already have the page */
> + if (rb != mis->last_rb) {
> + mis->last_rb = rb;
> + migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
> + aligned_rbo, pagesize);
> + } else {
> + /* Save some space */
> + migrate_send_rp_req_pages(mis, NULL, aligned_rbo, pagesize);
> + }
> + return 0;
> +}
> +
So IIUC this can only be called within the page fault thread or there
can be race. Is there a way to guarantee this? Or do we need a
comment for that?
> /*
> * Handle faults detected by the USERFAULT markings
> */
> @@ -544,9 +569,9 @@ static void *postcopy_ram_fault_thread(void *opaque)
> int ret;
> size_t index;
> RAMBlock *rb = NULL;
> - RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */
>
> trace_postcopy_ram_fault_thread_entry();
> + mis->last_rb = NULL; /* last RAMBlock we sent part of */
> qemu_sem_post(&mis->fault_thread_sem);
>
> struct pollfd *pfd;
> @@ -634,8 +659,8 @@ static void *postcopy_ram_fault_thread(void *opaque)
> * Send the request to the source - we want to request one
> * of our host page sizes (which is >= TPS)
> */
> - if (rb != last_rb) {
> - last_rb = rb;
> + if (rb != mis->last_rb) {
> + mis->last_rb = rb;
> migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
> rb_offset, qemu_ram_pagesize(rb));
> } else {
> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> index dbc2ee1f2b..4c63f20df4 100644
> --- a/migration/postcopy-ram.h
> +++ b/migration/postcopy-ram.h
> @@ -162,5 +162,8 @@ struct PostCopyFD {
> */
> void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
> void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
> +/* Callback from shared fault handlers to ask for a page */
> +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
> + uint64_t client_addr, uint64_t offset);
>
> #endif
> diff --git a/migration/trace-events b/migration/trace-events
> index 1e617ad7a6..7c910b5479 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -198,6 +198,8 @@ postcopy_ram_incoming_cleanup_closeuf(void) ""
> postcopy_ram_incoming_cleanup_entry(void) ""
> postcopy_ram_incoming_cleanup_exit(void) ""
> postcopy_ram_incoming_cleanup_join(void) ""
> +postcopy_request_shared_page(const char *sharer, const char *rb, uint64_t
> rb_offset) "for %s in %s offset 0x%"PRIx64
> +
> save_xbzrle_page_skipping(void) ""
> save_xbzrle_page_overflow(void) ""
> ram_save_iterate_big_wait(uint64_t milliconds, int iterations) "big wait: %"
> PRIu64 " milliseconds, %d iterations"
> --
> 2.14.3
>
--
Peter Xu
