| Message ID | 1372018280-133901-1-git-send-email-chegu_vinod@hp.com |
|---|---|
| State | New |
| Headers | show |
One nit and one question: Il 23/06/2013 22:11, Chegu Vinod ha scritto: > @@ -404,6 +413,23 @@ static void migration_bitmap_sync(void) > > /* more than 1 second = 1000 millisecons */ > if (end_time > start_time + 1000) { > + if (migrate_auto_converge()) { > + /* The following detection logic can be refined later. For now: > + Check to see if the dirtied bytes is 50% more than the approx. > + amount of bytes that just got transferred since the last time we > + were in this routine. If that happens >N times (for now N==4) > + we turn on the throttle down logic */ > + bytes_xfer_now = ram_bytes_transferred(); > + if (s->dirty_pages_rate && > + (num_dirty_pages_period * TARGET_PAGE_SIZE > > + (bytes_xfer_now - bytes_xfer_prev)/2) && > + (dirty_rate_high_cnt++ > 4)) { > + trace_migration_throttle(); > + mig_throttle_on = true; > + dirty_rate_high_cnt = 0; > + } > + bytes_xfer_prev = bytes_xfer_now; > + } Missing: else { mig_throttle_on = false; } > +/* Stub function that's gets run on the vcpu when its brought out of the > + VM to run inside qemu via async_run_on_cpu()*/ > +static void mig_sleep_cpu(void *opq) > +{ > + qemu_mutex_unlock_iothread(); > + g_usleep(30*1000); > + qemu_mutex_lock_iothread(); > +} > + > + /* If it has been more than 40 ms since the last time the guest > + * was throttled then do it again. > + */ > + if (40 < (t1-t0)/1000000) { You're stealing 75% of the CPU time, isn't that a lot? > + mig_throttle_guest_down(); > + t0 = t1; > + } > +} > Paolo
On 6/24/2013 6:01 AM, Paolo Bonzini wrote: > One nit and one question: > > Il 23/06/2013 22:11, Chegu Vinod ha scritto: >> @@ -404,6 +413,23 @@ static void migration_bitmap_sync(void) >> >> /* more than 1 second = 1000 millisecons */ >> if (end_time > start_time + 1000) { >> + if (migrate_auto_converge()) { >> + /* The following detection logic can be refined later. For now: >> + Check to see if the dirtied bytes is 50% more than the approx. >> + amount of bytes that just got transferred since the last time we >> + were in this routine. If that happens >N times (for now N==4) >> + we turn on the throttle down logic */ >> + bytes_xfer_now = ram_bytes_transferred(); >> + if (s->dirty_pages_rate && >> + (num_dirty_pages_period * TARGET_PAGE_SIZE > >> + (bytes_xfer_now - bytes_xfer_prev)/2) && >> + (dirty_rate_high_cnt++ > 4)) { >> + trace_migration_throttle(); >> + mig_throttle_on = true; >> + dirty_rate_high_cnt = 0; >> + } >> + bytes_xfer_prev = bytes_xfer_now; >> + } > > Missing: > > else { > mig_throttle_on = false; > } Ok. >> +/* Stub function that's gets run on the vcpu when its brought out of the >> + VM to run inside qemu via async_run_on_cpu()*/ >> +static void mig_sleep_cpu(void *opq) >> +{ >> + qemu_mutex_unlock_iothread(); >> + g_usleep(30*1000); >> + qemu_mutex_lock_iothread(); >> +} >> + >> + /* If it has been more than 40 ms since the last time the guest >> + * was throttled then do it again. >> + */ >> + if (40 < (t1-t0)/1000000) { > You're stealing 75% of the CPU time, isn't that a lot? Depends on the dirty rate vs. transfer rate... I had tried 50% too and it took much longer for the migration to converge. Vinod > >> + mig_throttle_guest_down(); >> + t0 = t1; >> + } >> +} >> > Paolo > > . >
Il 24/06/2013 15:08, Chegu Vinod ha scritto: > On 6/24/2013 6:01 AM, Paolo Bonzini wrote: >> One nit and one question: >> >> Il 23/06/2013 22:11, Chegu Vinod ha scritto: >>> @@ -404,6 +413,23 @@ static void migration_bitmap_sync(void) >>> /* more than 1 second = 1000 millisecons */ >>> if (end_time > start_time + 1000) { >>> + if (migrate_auto_converge()) { >>> + /* The following detection logic can be refined later. >>> For now: >>> + Check to see if the dirtied bytes is 50% more than >>> the approx. >>> + amount of bytes that just got transferred since the >>> last time we >>> + were in this routine. If that happens >N times (for >>> now N==4) >>> + we turn on the throttle down logic */ >>> + bytes_xfer_now = ram_bytes_transferred(); >>> + if (s->dirty_pages_rate && >>> + (num_dirty_pages_period * TARGET_PAGE_SIZE > >>> + (bytes_xfer_now - bytes_xfer_prev)/2) && >>> + (dirty_rate_high_cnt++ > 4)) { >>> + trace_migration_throttle(); >>> + mig_throttle_on = true; >>> + dirty_rate_high_cnt = 0; >>> + } >>> + bytes_xfer_prev = bytes_xfer_now; >>> + } >> >> Missing: >> >> else { >> mig_throttle_on = false; >> } > > Ok. >>> +/* Stub function that's gets run on the vcpu when its brought out of >>> the >>> + VM to run inside qemu via async_run_on_cpu()*/ >>> +static void mig_sleep_cpu(void *opq) >>> +{ >>> + qemu_mutex_unlock_iothread(); >>> + g_usleep(30*1000); >>> + qemu_mutex_lock_iothread(); >>> +} >>> + >>> + /* If it has been more than 40 ms since the last time the guest >>> + * was throttled then do it again. >>> + */ >>> + if (40 < (t1-t0)/1000000) { >> You're stealing 75% of the CPU time, isn't that a lot? > > Depends on the dirty rate vs. transfer rate... I had tried 50% too and > it took much longer for the migration to converge. Fair enough, thanks! Paolo
diff --git a/arch_init.c b/arch_init.c index a8b91ee..e7ca3b1 100644 --- a/arch_init.c +++ b/arch_init.c @@ -104,6 +104,9 @@ int graphic_depth = 15; #endif const uint32_t arch_type = QEMU_ARCH; +static bool mig_throttle_on; +static int dirty_rate_high_cnt; +static void check_guest_throttling(void); /***********************************************************/ /* ram save/restore */ @@ -378,8 +381,14 @@ static void migration_bitmap_sync(void) uint64_t num_dirty_pages_init = migration_dirty_pages; MigrationState *s = migrate_get_current(); static int64_t start_time; + static int64_t bytes_xfer_prev; static int64_t num_dirty_pages_period; int64_t end_time; + int64_t bytes_xfer_now; + + if (!bytes_xfer_prev) { + bytes_xfer_prev = ram_bytes_transferred(); + } if (!start_time) { start_time = qemu_get_clock_ms(rt_clock); @@ -404,6 +413,23 @@ static void migration_bitmap_sync(void) /* more than 1 second = 1000 millisecons */ if (end_time > start_time + 1000) { + if (migrate_auto_converge()) { + /* The following detection logic can be refined later. For now: + Check to see if the dirtied bytes is 50% more than the approx. + amount of bytes that just got transferred since the last time we + were in this routine. If that happens >N times (for now N==4) + we turn on the throttle down logic */ + bytes_xfer_now = ram_bytes_transferred(); + if (s->dirty_pages_rate && + (num_dirty_pages_period * TARGET_PAGE_SIZE > + (bytes_xfer_now - bytes_xfer_prev)/2) && + (dirty_rate_high_cnt++ > 4)) { + trace_migration_throttle(); + mig_throttle_on = true; + dirty_rate_high_cnt = 0; + } + bytes_xfer_prev = bytes_xfer_now; + } s->dirty_pages_rate = num_dirty_pages_period * 1000 / (end_time - start_time); s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE; @@ -566,6 +592,8 @@ static int ram_save_setup(QEMUFile *f, void *opaque) migration_bitmap = bitmap_new(ram_pages); bitmap_set(migration_bitmap, 0, ram_pages); migration_dirty_pages = ram_pages; + mig_throttle_on = false; + dirty_rate_high_cnt = 0; if (migrate_use_xbzrle()) { XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() / @@ -628,6 +656,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque) } total_sent += bytes_sent; acct_info.iterations++; + check_guest_throttling(); /* we want to check in the 1st loop, just in case it was the 1st time and we had to sync the dirty bitmap. qemu_get_clock_ns() is a bit expensive, so we only check each some @@ -1097,3 +1126,53 @@ TargetInfo *qmp_query_target(Error **errp) return info; } + +/* Stub function that's gets run on the vcpu when its brought out of the + VM to run inside qemu via async_run_on_cpu()*/ +static void mig_sleep_cpu(void *opq) +{ + qemu_mutex_unlock_iothread(); + g_usleep(30*1000); + qemu_mutex_lock_iothread(); +} + +/* To reduce the dirty rate explicitly disallow the VCPUs from spending + much time in the VM. The migration thread will try to catchup. + Workload will experience a performance drop. +*/ +static void mig_throttle_cpu_down(CPUState *cpu, void *data) +{ + async_run_on_cpu(cpu, mig_sleep_cpu, NULL); +} + +static void mig_throttle_guest_down(void) +{ + qemu_mutex_lock_iothread(); + qemu_for_each_cpu(mig_throttle_cpu_down, NULL); + qemu_mutex_unlock_iothread(); +} + +static void check_guest_throttling(void) +{ + static int64_t t0; + int64_t t1; + + if (!mig_throttle_on) { + return; + } + + if (!t0) { + t0 = qemu_get_clock_ns(rt_clock); + return; + } + + t1 = qemu_get_clock_ns(rt_clock); + + /* If it has been more than 40 ms since the last time the guest + * was throttled then do it again. + */ + if (40 < (t1-t0)/1000000) { + mig_throttle_guest_down(); + t0 = t1; + } +}
If a user chooses to turn on the auto-converge migration capability these changes detect the lack of convergence and throttle down the guest. i.e. force the VCPUs out of the guest for some duration and let the migration thread catchup and help converge. Verified the convergence using the following : - Java Warehouse workload running on a 20VCPU/256G guest(~80% busy) - OLTP like workload running on a 80VCPU/512G guest (~80% busy) Sample results with Java warehouse workload : (migrate speed set to 20Gb and migrate downtime set to 4seconds). (qemu) info migrate capabilities: xbzrle: off auto-converge: off <---- Migration status: active total time: 1487503 milliseconds expected downtime: 519 milliseconds transferred ram: 383749347 kbytes remaining ram: 2753372 kbytes total ram: 268444224 kbytes duplicate: 65461532 pages skipped: 64901568 pages normal: 95750218 pages normal bytes: 383000872 kbytes dirty pages rate: 67551 pages --- (qemu) info migrate capabilities: xbzrle: off auto-converge: on <---- Migration status: completed total time: 241161 milliseconds downtime: 6373 milliseconds transferred ram: 28235307 kbytes remaining ram: 0 kbytes total ram: 268444224 kbytes duplicate: 64946416 pages skipped: 64903523 pages normal: 7044971 pages normal bytes: 28179884 kbytes Signed-off-by: Chegu Vinod <chegu_vinod@hp.com> --- arch_init.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 79 insertions(+), 0 deletions(-)