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migration: allow fault thread to pause

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Allows the fault thread to stop handling page faults temporarily. When
network failure happened (and if we expect a recovery afterwards), we
should not allow the fault thread to continue sending things to source,
instead, it should halt for a while until the connection is rebuilt.

When the dest main thread noticed the failure, it kicks the fault thread
to switch to pause state.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-7-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Xu 2018-05-02 18:47:22 +08:00 • committed by Juan Quintela
parent 14b1742eaa
commit 3a7804c306
5 changed files with 57 additions and 4 deletions
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54
migration/postcopy-ram.c
View file

@ -830,6 +830,17 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
affected_cpu);
}
static bool postcopy_pause_fault_thread(MigrationIncomingState *mis)
{
trace_postcopy_pause_fault_thread();
qemu_sem_wait(&mis->postcopy_pause_sem_fault);
trace_postcopy_pause_fault_thread_continued();
return true;
}
/*
* Handle faults detected by the USERFAULT markings
*/
@ -880,6 +891,22 @@ static void *postcopy_ram_fault_thread(void *opaque)
break;
}
if (!mis->to_src_file) {
/*
* Possibly someone tells us that the return path is
* broken already using the event. We should hold until
* the channel is rebuilt.
*/
if (postcopy_pause_fault_thread(mis)) {
mis->last_rb = NULL;
/* Continue to read the userfaultfd */
} else {
error_report("%s: paused but don't allow to continue",
__func__);
break;
}
}
if (pfd[1].revents) {
uint64_t tmp64 = 0;
@ -942,18 +969,37 @@ static void *postcopy_ram_fault_thread(void *opaque)
(uintptr_t)(msg.arg.pagefault.address),
msg.arg.pagefault.feat.ptid, rb);
retry:
/*
* Send the request to the source - we want to request one
* of our host page sizes (which is >= TPS)
*/
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));
ret = migrate_send_rp_req_pages(mis,
qemu_ram_get_idstr(rb),
rb_offset,
qemu_ram_pagesize(rb));
} else {
/* Save some space */
migrate_send_rp_req_pages(mis, NULL,
rb_offset, qemu_ram_pagesize(rb));
ret = migrate_send_rp_req_pages(mis,
NULL,
rb_offset,
qemu_ram_pagesize(rb));
}
if (ret) {
/* May be network failure, try to wait for recovery */
if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
/* We got reconnected somehow, try to continue */
mis->last_rb = NULL;
goto retry;
} else {
/* This is a unavoidable fault */
error_report("%s: migrate_send_rp_req_pages() get %d",
__func__, ret);
break;
}
}
}