* Alexey Perevalov (a.pereva...@samsung.com) wrote:
> This patch provides blocktime calculation per vCPU,
> as a summary and as a overlapped value for all vCPUs.
>
> This approach was suggested by Peter Xu, as an improvements of
> previous approch where QEMU kept tree with faulted page address and cpus
> bitmask
> in it. Now QEMU is keeping array with faulted page address as value and vCPU
> as index. It helps to find proper vCPU at UFFD_COPY time. Also it keeps
> list for blocktime per vCPU (could be traced with page_fault_addr)
>
> Blocktime will not calculated if postcopy_blocktime field of
> MigrationIncomingState wasn't initialized.
>
> Signed-off-by: Alexey Perevalov <a.pereva...@samsung.com>
I think this is mostly ok now, minor comments below;
> ---
> migration/postcopy-ram.c | 139
> ++++++++++++++++++++++++++++++++++++++++++++++-
> migration/trace-events | 5 +-
> 2 files changed, 142 insertions(+), 2 deletions(-)
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 62a272a..0ad9f9f 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -27,6 +27,7 @@
> #include "ram.h"
> #include "sysemu/sysemu.h"
> #include "sysemu/balloon.h"
> +#include <sys/param.h>
> #include "qemu/error-report.h"
> #include "trace.h"
>
> @@ -561,6 +562,133 @@ static int ram_block_enable_notify(const char
> *block_name, void *host_addr,
> return 0;
> }
>
> +static int get_mem_fault_cpu_index(uint32_t pid)
> +{
> + CPUState *cpu_iter;
> +
> + CPU_FOREACH(cpu_iter) {
> + if (cpu_iter->thread_id == pid) {
> + return cpu_iter->cpu_index;
> + }
> + }
> + trace_get_mem_fault_cpu_index(pid);
> + return -1;
> +}
> +
> +/*
> + * This function is being called when pagefault occurs. It
> + * tracks down vCPU blocking time.
> + *
> + * @addr: faulted host virtual address
> + * @ptid: faulted process thread id
> + * @rb: ramblock appropriate to addr
> + */
> +static void mark_postcopy_blocktime_begin(uint64_t addr, uint32_t ptid,
> + RAMBlock *rb)
> +{
> + int cpu;
> + MigrationIncomingState *mis = migration_incoming_get_current();
> + PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
> + int64_t now_ms;
> +
> + if (!dc || ptid == 0) {
> + return;
> + }
> + cpu = get_mem_fault_cpu_index(ptid);
> + if (cpu < 0) {
> + return;
> + }
> +
> + now_ms = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> + if (dc->vcpu_addr[cpu] == 0) {
> + atomic_inc(&dc->smp_cpus_down);
> + }
> +
> + atomic_xchg__nocheck(&dc->vcpu_addr[cpu], addr);
> + atomic_xchg__nocheck(&dc->last_begin, now_ms);
> + atomic_xchg__nocheck(&dc->page_fault_vcpu_time[cpu], now_ms);
> +
> + if (test_copiedmap_by_addr(addr, rb)) {
> + atomic_xchg__nocheck(&dc->vcpu_addr[cpu], 0);
> + atomic_xchg__nocheck(&dc->page_fault_vcpu_time[cpu], 0);
> + atomic_sub(&dc->smp_cpus_down, 1);
> + }
> + trace_mark_postcopy_blocktime_begin(addr, dc,
> dc->page_fault_vcpu_time[cpu],
> + cpu);
You could add a flag to the trace to help let you know if you hit the
'copiedmap' case.
> +}
> +
> +/*
> + * This function just provide calculated blocktime per cpu and trace it.
> + * Total blocktime is calculated in mark_postcopy_blocktime_end.
> + *
> + *
> + * Assume we have 3 CPU
> + *
> + * S1 E1 S1 E1
> + * -----***********------------xxx***************------------------------>
> CPU1
> + *
> + * S2 E2
> + * ------------****************xxx--------------------------------------->
> CPU2
> + *
> + * S3 E3
> + * ------------------------****xxx********------------------------------->
> CPU3
> + *
> + * We have sequence S1,S2,E1,S3,S1,E2,E3,E1
> + * S2,E1 - doesn't match condition due to sequence S1,S2,E1 doesn't include
> CPU3
> + * S3,S1,E2 - sequence includes all CPUs, in this case overlap will be S1,E2
> -
> + * it's a part of total blocktime.
> + * S1 - here is last_begin
> + * Legend of the picture is following:
> + * * - means blocktime per vCPU
> + * x - means overlapped blocktime (total blocktime)
> + *
> + * @addr: host virtual address
> + */
> +static void mark_postcopy_blocktime_end(uint64_t addr)
> +{
> + MigrationIncomingState *mis = migration_incoming_get_current();
> + PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
> + int i, affected_cpu = 0;
> + int64_t now_ms;
> + bool vcpu_total_blocktime = false;
> +
> + if (!dc) {
> + return;
> + }
> +
> + now_ms = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> +
> + /* lookup cpu, to clear it,
> + * that algorithm looks straighforward, but it's not
> + * optimal, more optimal algorithm is keeping tree or hash
> + * where key is address value is a list of */
> + for (i = 0; i < smp_cpus; i++) {
> + uint64_t vcpu_blocktime = 0;
> + if (atomic_fetch_add(&dc->vcpu_addr[i], 0) != addr) {
> + continue;
> + }
> + atomic_xchg__nocheck(&dc->vcpu_addr[i], 0);
> + vcpu_blocktime = now_ms -
> + atomic_fetch_add(&dc->page_fault_vcpu_time[i], 0);
> + affected_cpu += 1;
> + /* we need to know is that mark_postcopy_end was due to
> + * faulted page, another possible case it's prefetched
> + * page and in that case we shouldn't be here */
> + if (!vcpu_total_blocktime &&
> + atomic_fetch_add(&dc->smp_cpus_down, 0) == smp_cpus) {
> + vcpu_total_blocktime = true;
> + }
> + /* continue cycle, due to one page could affect several vCPUs */
> + dc->vcpu_blocktime[i] += vcpu_blocktime;
> + }
> +
> + atomic_sub(&dc->smp_cpus_down, affected_cpu);
> + if (vcpu_total_blocktime) {
> + dc->total_blocktime += now_ms - atomic_fetch_add(&dc->last_begin, 0);
> + }
> + trace_mark_postcopy_blocktime_end(addr, dc, dc->total_blocktime);
you could add affected_cpu to the trace.
> +}
> +
> /*
> * Handle faults detected by the USERFAULT markings
> */
> @@ -638,8 +766,11 @@ static void *postcopy_ram_fault_thread(void *opaque)
> rb_offset &= ~(qemu_ram_pagesize(rb) - 1);
> trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
> qemu_ram_get_idstr(rb),
> - rb_offset);
> + rb_offset,
> + msg.arg.pagefault.feat.ptid);
>
> + mark_postcopy_blocktime_begin((uintptr_t)(msg.arg.pagefault.address),
> + msg.arg.pagefault.feat.ptid, rb);
> /*
> * Send the request to the source - we want to request one
> * of our host page sizes (which is >= TPS)
> @@ -723,6 +854,12 @@ int postcopy_place_page(MigrationIncomingState *mis,
> void *host, void *from,
> copy_struct.len = pagesize;
> copy_struct.mode = 0;
>
> + /* copied page isn't feature of blocktime calculation,
> + * it's more general entity, so keep it here,
> + * but gup betwean two following operation could be high,
^---gap ?
Dave
> + * and in this case blocktime for such small interval will be lost */
> + set_copiedmap_by_addr((uint64_t)(uintptr_t)host, rb);
> + mark_postcopy_blocktime_end((uint64_t)(uintptr_t)host);
> /* copy also acks to the kernel waking the stalled thread up
> * TODO: We can inhibit that ack and only do it if it was requested
> * which would be slightly cheaper, but we'd have to be careful
> diff --git a/migration/trace-events b/migration/trace-events
> index 5b8ccf3..7bdadbb 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -112,6 +112,8 @@ process_incoming_migration_co_end(int ret, int ps)
> "ret=%d postcopy-state=%d"
> process_incoming_migration_co_postcopy_end_main(void) ""
> migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p
> ioctype=%s"
> migration_set_outgoing_channel(void *ioc, const char *ioctype, const char
> *hostname) "ioc=%p ioctype=%s hostname=%s"
> +mark_postcopy_blocktime_begin(uint64_t addr, void *dd, int64_t time, int
> cpu) "addr 0x%" PRIx64 " dd %p time %" PRId64 " cpu %d"
> +mark_postcopy_blocktime_end(uint64_t addr, void *dd, int64_t time) "addr
> 0x%" PRIx64 " dd %p time %" PRId64
>
> # migration/rdma.c
> qemu_rdma_accept_incoming_migration(void) ""
> @@ -188,7 +190,7 @@ postcopy_ram_enable_notify(void) ""
> postcopy_ram_fault_thread_entry(void) ""
> postcopy_ram_fault_thread_exit(void) ""
> postcopy_ram_fault_thread_quit(void) ""
> -postcopy_ram_fault_thread_request(uint64_t hostaddr, const char *ramblock,
> size_t offset) "Request for HVA=%" PRIx64 " rb=%s offset=%zx"
> +postcopy_ram_fault_thread_request(uint64_t hostaddr, const char *ramblock,
> size_t offset, uint32_t pid) "Request for HVA=%" PRIx64 " rb=%s offset=%zx %u"
> postcopy_ram_incoming_cleanup_closeuf(void) ""
> postcopy_ram_incoming_cleanup_entry(void) ""
> postcopy_ram_incoming_cleanup_exit(void) ""
> @@ -197,6 +199,7 @@ 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"
> ram_load_complete(int ret, uint64_t seq_iter) "exit_code %d seq iteration %"
> PRIu64
> +get_mem_fault_cpu_index(uint32_t pid) "pid %u is not vCPU"
>
> # migration/exec.c
> migration_exec_outgoing(const char *cmd) "cmd=%s"
> --
> 1.9.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
