+ Radek, Sam, in case they are interested.
On Fri, Jan 10, 2020 at 12:18 AM Roman Penyaev <rpenyaev@xxxxxxx> wrote:
>
> Subject: crimson-osd vs legacy-osd: should the perf difference be
> already noticeable?
>
> Hi folks,
>
> I was curios to read some early performance benchmarks which compare
> crimson-osd vs legacy-osd, but could not find any. So eventually
> decided to do my own micro benchmarks in order to test transport
> together with PG layer, avoiding any storage costs completely
> (no reason to test memcpy of memstore which is the only available
> objectstore for crimson). At least recalling all these ad brochures
> of seastar which should bring performance on another level by doing
> preemption in userspace, the difference should be already there and
> visible in numbers.
>
> And yes I'm aware that crimson is in development, but if basic
> functionality is already supported (like write path), then I can
> squeeze some numbers.
>
> For all testing loads I run original rbd.fio, taken from fio/examples/,
> of course changing only block size. Since this is a micro benchmark I
> run only 1 osd cluster.
>
> [global]
> ioengine=rbd
> clientname=admin
> pool=rbd
> rbdname=fio_test
> rw=randwrite
> #bs=4k
>
> [rbd_iodepth32]
> iodepth=32
>
>
> -- Part 1, turn MemStore and cyan_store into null block
>
> Testing memcpy is not interesting so in order to run any memstore with
> 'memstore_debug_omit_block_device_write=true' option set and skip all
> writes I have to do a small tweak in order to start osd, namely I still
> need to pass small writes and omit big ones which are sent by the
> client,
> something as the following:
>
> - if (len > 0 && !local_conf()->memstore_debug_omit_block_device_write)
> {
> +
> + if (len > 0 &&
> + (!local_conf()->memstore_debug_omit_block_device_write ||
> + // We still want cluster meta-data to be saved, so pass only
> small
> + // writes, expecting user writes will be >= 4k.
> + len < 4096)) {
>
>
> *** BTW at the bottom you can find the whole patch with all debug
> modifications made to deliver these numbers.
>
>
> # legacy-osd, MemStore
>
> MON=1 MDS=0 OSD=1 MGR=1 ../src/vstart.sh --memstore -n \
> -o 'memstore_debug_omit_block_device_write=true'
>
> 4k IOPS=42.7k, BW=167MiB/s, Lat=749.18usec
> 8k IOPS=40.2k, BW=314MiB/s, Lat=795.03usec
> 16k IOPS=37.6k, BW=588MiB/s, Lat=849.12usec
> 32k IOPS=32.0k, BW=1000MiB/s, Lat=998.56usec
> 64k IOPS=25.5k, BW=1594MiB/s, Lat=1253.99usec
> 128k IOPS=17.5k, BW=2188MiB/s, Lat=1826.54usec
> 256k IOPS=10.1k, BW=2531MiB/s, Lat=3157.33usec
> 512k IOPS=5252, BW=2626MiB/s, Lat=6071.37usec
> 1m IOPS=2656, BW=2656MiB/s, Lat=12029.65usec
>
>
> # crimson-osd, cyan_store
>
> MON=1 MDS=0 OSD=1 MGR=1 ../src/vstart.sh --crimson --memstore -n \
> -o 'memstore_debug_omit_block_device_write=true'
>
> 4k IOPS=40.2k, BW=157MiB/s, Lat=796.07usec
> 8k IOPS=37.1k, BW=290MiB/s, Lat=861.51usec
> 16k IOPS=32.9k, BW=514MiB/s, Lat=970.99usec
> 32k IOPS=26.1k, BW=815MiB/s, Lat=1225.78usec
> 64k IOPS=21.3k, BW=1333MiB/s, Lat=1498.92usec
> 128k IOPS=14.4k, BW=1795MiB/s, Lat=2227.07usec
> 256k IOPS=6143, BW=1536MiB/s, Lat=5203.70usec
> 512k IOPS=3776, BW=1888MiB/s, Lat=8464.79usec
> 1m IOPS=1866, BW=1867MiB/s, Lat=17126.36usec
>
>
> First thing that catches my eye is that for small blocks there is no big
> difference at all, but as the block increases, crimsons iops starts to
that's also our findings. and it's expected. as async messenger uses
the same reactor model as seastar does. actually its original
implementation was adapted from seastar's socket stream
implementation.
> decline. Can it be the transport issue? Can be tested as well.
because seastar's socket facility reads from the wire with 4K chunk
size, while classic OSD's async messenger reads the payload with the
size suggested by the header. so when it comes to larger block size,
it takes crimson-osd multiple syscalls and memcpy calls to read the
request from wire, that's why classic OSD wins in this case.
>
>
> -- Part 2, complete writes immediately, even not leaving the transport
>
> Would be great to avoid PG logic costs, exactly like we did for
> objectstore,
> i.e. the following question can be asked "how fast we can handle writes
> and
> complete them immediately from the transport callback and measure socket
> read/write costs?". I introduced new option 'osd_immediate_completions'
> and handle it directly from 'OSD::ms_[fast_]dispatch' function replying
> with
> success just immediately (for details see patch at the bottom).
>
>
> # legacy-osd
>
> MON=1 MDS=0 OSD=1 MGR=1 ../src/vstart.sh --memstore -n \
> -o 'osd_immediate_completions=true'
>
> 4k IOPS=59.2k, BW=231MiB/s, Lat=539.68usec
> 8k IOPS=55.1k, BW=430MiB/s, Lat=580.44usec
> 16k IOPS=50.5k, BW=789MiB/s, Lat=633.03usec
> 32k IOPS=44.6k, BW=1394MiB/s, Lat=716.74usec
> 64k IOPS=33.5k, BW=2093MiB/s, Lat=954.60usec
> 128k IOPS=20.8k, BW=2604MiB/s, Lat=1535.01usec
> 256k IOPS=10.6k, BW=2642MiB/s, Lat=3026.19usec
> 512k IOPS=5400, BW=2700MiB/s, Lat=5920.86usec
> 1m IOPS=2549, BW=2550MiB/s, Lat=12539.40usec
>
>
> # crimson-osd
>
> MON=1 MDS=0 OSD=1 MGR=1 ../src/vstart.sh --crimson --memstore -n \
> -o 'osd_immediate_completions=true'
>
> 4k IOPS=60.2k, BW=235MiB/s, Lat=530.95usec
> 8k IOPS=52.0k, BW=407MiB/s, Lat=614.21usec
> 16k IOPS=47.1k, BW=736MiB/s, Lat=678.41usec
> 32k IOPS=37.8k, BW=1180MiB/s, Lat=846.75usec
> 64k IOPS=26.6k, BW=1660MiB/s, Lat=1203.51usec
> 128k IOPS=15.5k, BW=1936MiB/s, Lat=2064.12usec
> 256k IOPS=7506, BW=1877MiB/s, Lat=4259.19usec
> 512k IOPS=3941, BW=1971MiB/s, Lat=8112.67usec
> 1m IOPS=1785, BW=1786MiB/s, Lat=17896.44usec
>
>
> As a summary I can say that for me is quite surprising not to notice any
> iops improvements on crimson side (not to mention the problem with
> reading
> of big blocks). Since I run only 1 osd on one particular load I admit
> the
> artificial nature of such tests (thus called micro benchmark), but then
> on what cluster scale and what benchmark can I run to see some
> improvements
> of a new architecture?
have you tried to use multiple fio clients to saturate CPU capacity of
OSD nodes?
>
> Roman
>
> ---
> src/common/options.cc | 4 ++++
> src/crimson/os/cyan_store.cc | 6 +++++-
> src/crimson/osd/ops_executer.cc | 4 ++--
> src/crimson/osd/osd.cc | 20 ++++++++++++++++++++
> src/os/memstore/MemStore.cc | 6 +++++-
> src/osd/OSD.cc | 24 ++++++++++++++++++++++++
> 6 files changed, 60 insertions(+), 4 deletions(-)
>
> diff --git a/src/common/options.cc b/src/common/options.cc
> index d91827c1a803..769666d2955c 100644
> --- a/src/common/options.cc
> +++ b/src/common/options.cc
> @@ -4234,6 +4234,10 @@ std::vector<Option> get_global_options() {
> .set_default(false)
> .set_description(""),
>
> + Option("osd_immediate_completions", Option::TYPE_BOOL,
> Option::LEVEL_ADVANCED)
> + .set_default(false)
> + .set_description(""),
> +
> // --------------------------
> // bluestore
>
> diff --git a/src/crimson/os/cyan_store.cc b/src/crimson/os/cyan_store.cc
> index f0749cb921f9..c05e0e40b721 100644
> --- a/src/crimson/os/cyan_store.cc
> +++ b/src/crimson/os/cyan_store.cc
> @@ -463,7 +463,11 @@ int CyanStore::_write(const coll_t& cid, const
> ghobject_t& oid,
> return -ENOENT;
>
> ObjectRef o = c->get_or_create_object(oid);
> - if (len > 0 && !local_conf()->memstore_debug_omit_block_device_write)
> {
> + if (len > 0 &&
> + (!local_conf()->memstore_debug_omit_block_device_write ||
> + // We still want cluster meta-data to be saved, so pass only
> small
> + // writes, expecting user writes will be >= 4k.
> + len < 4096)) {
> const ssize_t old_size = o->get_size();
> o->write(offset, bl);
> used_bytes += (o->get_size() - old_size);
> diff --git a/src/crimson/osd/ops_executer.cc
> b/src/crimson/osd/ops_executer.cc
> index 13f6f086c4ea..a76fc6e206d8 100644
> --- a/src/crimson/osd/ops_executer.cc
> +++ b/src/crimson/osd/ops_executer.cc
> @@ -431,8 +431,8 @@ OpsExecuter::execute_osd_op(OSDOp& osd_op)
>
> default:
> logger().warn("unknown op {}", ceph_osd_op_name(op.op));
> - throw std::runtime_error(
> - fmt::format("op '{}' not supported", ceph_osd_op_name(op.op)));
> + // Without that `fio examples/rbd.fio` hangs on exit
> + throw ceph::osd::operation_not_supported{};
> }
> }
>
> diff --git a/src/crimson/osd/osd.cc b/src/crimson/osd/osd.cc
> index ddd8742d1a74..737cc266766e 100644
> --- a/src/crimson/osd/osd.cc
> +++ b/src/crimson/osd/osd.cc
> @@ -17,6 +17,7 @@
> #include "messages/MOSDOp.h"
> #include "messages/MOSDPGLog.h"
> #include "messages/MOSDRepOpReply.h"
> +#include "messages/MOSDOpReply.h"
> #include "messages/MPGStats.h"
>
> #include "os/Transaction.h"
> @@ -881,6 +882,25 @@ seastar::future<> OSD::committed_osd_maps(version_t
> first,
> seastar::future<> OSD::handle_osd_op(ceph::net::Connection* conn,
> Ref<MOSDOp> m)
> {
> +
> + //
> + // Immediately complete requests even without leaving the transport
> + //
> + if (local_conf().get_val<bool>("osd_immediate_completions")) {
> + m->finish_decode();
> +
> + for (auto op : m->ops) {
> + if (op.op.op == CEPH_OSD_OP_WRITE &&
> + // Complete big writes only
> + op.op.extent.length >= 4096) {
> +
> + auto reply = make_message<MOSDOpReply>(m.get(), 0,
> osdmap->get_epoch(),
> + CEPH_OSD_FLAG_ACK |
> CEPH_OSD_FLAG_ONDISK, true);
> + return conn->send(reply);
> + }
> + }
> + }
> +
> shard_services.start_operation<ClientRequest>(
> *this,
> conn->get_shared(),
> diff --git a/src/os/memstore/MemStore.cc b/src/os/memstore/MemStore.cc
> index 05d16edb6cc0..265dc64c808d 100644
> --- a/src/os/memstore/MemStore.cc
> +++ b/src/os/memstore/MemStore.cc
> @@ -1047,7 +1047,11 @@ int MemStore::_write(const coll_t& cid, const
> ghobject_t& oid,
> return -ENOENT;
>
> ObjectRef o = c->get_or_create_object(oid);
> - if (len > 0 && !cct->_conf->memstore_debug_omit_block_device_write) {
> + if (len > 0 &&
> + (!cct->_conf->memstore_debug_omit_block_device_write ||
> + // We still want cluster meta-data to be saved, so pass only
> small
> + // writes, expecting user writes will be bigger than 4k.
> + len < 4096)) {
> const ssize_t old_size = o->get_size();
> o->write(offset, bl);
> used_bytes += (o->get_size() - old_size);
> diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
> index 96aed0b706e3..796bf927126f 100644
> --- a/src/osd/OSD.cc
> +++ b/src/osd/OSD.cc
> @@ -7223,6 +7223,30 @@ void OSD::ms_fast_dispatch(Message *m)
> return;
> }
>
> + //
> + // Immediately complete requests even without leaving the transport
> + //
> + if (g_conf().get_val<bool>("osd_immediate_completions") &&
> + m->get_type() == CEPH_MSG_OSD_OP) {
> + MOSDOp *osdop = static_cast<MOSDOp*>(m);
> +
> + osdop->finish_decode();
> +
> + for (auto op : osdop->ops) {
> + if (op.op.op == CEPH_OSD_OP_WRITE &&
> + // Complete big writes only
> + op.op.extent.length >= 4096) {
> + MOSDOpReply *reply;
> +
> + reply = new MOSDOpReply(osdop, 0, osdmap->get_epoch(),
> + CEPH_OSD_FLAG_ACK |
> CEPH_OSD_FLAG_ONDISK, true);
> + osdop->get_connection()->send_message(reply);
> + m->put();
> + return;
> + }
> + }
> + }
> +
> // peering event?
> switch (m->get_type()) {
> case CEPH_MSG_PING:
>
--
Regards
Kefu Chai
