[dpdk-dev] [PATCH v3] Add in_flight_bitmask so as to use full 32 bits of tag.
jigsaw
jigsaw at gmail.com
Tue Nov 11 09:53:40 CET 2014
Hi Bruce,
This patch has little, if any, performance impact.
See the perf stat -d for original and patched version
of test_distributor_perf.
Original version
============
perf stat -d ./test_orig -cffff -n2
============
==== Cache line switch test ===
[4/4590]
Time for 1048576 iterations = 362349056 ticks
Ticks per iteration = 345
=== Performance test of distributor ===
Time per burst: 7043
Time per packet: 220
Worker 0 handled 3377372 packets
Worker 1 handled 2857280 packets
Worker 2 handled 2120982 packets
Worker 3 handled 2112720 packets
Worker 4 handled 2102014 packets
Worker 5 handled 2101314 packets
Worker 6 handled 2099248 packets
Worker 7 handled 2098560 packets
Worker 8 handled 2098114 packets
Worker 9 handled 2097962 packets
Worker 10 handled 2097892 packets
Worker 11 handled 2097856 packets
Worker 12 handled 2097762 packets
Worker 13 handled 2097726 packets
Worker 14 handled 2097630 packets
Total packets: 33554432 (2000000)
=== Perf test done ===
Performance counter stats for './test_orig -cffff -n2 --no-huge':
45784.935475 task-clock # 12.847 CPUs utilized
4822 context-switches # 0.105 K/sec
7 CPU-migrations # 0.000 K/sec
1017 page-faults # 0.022 K/sec
118181375409 cycles # 2.581 GHz
[40.00%]
88915381373 stalled-cycles-frontend # 75.24% frontend cycles
idle [39.98%]
77015854611 stalled-cycles-backend # 65.17% backend cycles
idle [39.96%]
30469536186 instructions # 0.26 insns per cycle
# 2.92 stalled cycles per
insn [49.96%]
6481829773 branches # 141.571 M/sec
[49.97%]
45283365 branch-misses # 0.70% of all branches
[50.00%]
6537115556 L1-dcache-loads # 142.779 M/sec
[50.05%]
249533128 L1-dcache-load-misses # 3.82% of all L1-dcache
hits [50.08%]
144469663 LLC-loads # 3.155 M/sec
[40.05%]
69897760 LLC-load-misses # 48.38% of all LL-cache
hits [40.03%]
3.563886431 seconds time elapsed
Patched version
=============
perf stat -d ./test_patch -cffff -n2
==== Cache line switch test ===
[4/4747]
Time for 1048576 iterations = 456390606 ticks
Ticks per iteration = 435
=== Performance test of distributor ===
Time per burst: 6566
Time per packet: 205
Worker 0 handled 2528418 packets
Worker 1 handled 2531906 packets
Worker 2 handled 2524133 packets
Worker 3 handled 2507720 packets
Worker 4 handled 2332648 packets
Worker 5 handled 2300046 packets
Worker 6 handled 2213035 packets
Worker 7 handled 2125486 packets
Worker 8 handled 2096726 packets
Worker 9 handled 2089150 packets
Worker 10 handled 2079626 packets
Worker 11 handled 2074512 packets
Worker 12 handled 2073560 packets
Worker 13 handled 2054838 packets
Worker 14 handled 2022628 packets
Total packets: 33554432 (2000000)
=== Perf test done ===
Performance counter stats for './test_patch -cffff -n2 --no-huge':
42784.064267 task-clock # 12.546 CPUs utilized
4517 context-switches # 0.106 K/sec
5 CPU-migrations # 0.000 K/sec
1020 page-faults # 0.024 K/sec
110531300647 cycles # 2.583 GHz
[40.06%]
83135557406 stalled-cycles-frontend # 75.21% frontend cycles
idle [40.02%]
71862086289 stalled-cycles-backend # 65.02% backend cycles
idle [39.99%]
28847200612 instructions # 0.26 insns per cycle
# 2.88 stalled cycles per
insn [49.98%]
6059139104 branches # 141.621 M/sec
[49.94%]
38455463 branch-misses # 0.63% of all branches
[49.95%]
6090169906 L1-dcache-loads # 142.347 M/sec
[49.99%]
235094118 L1-dcache-load-misses # 3.86% of all L1-dcache
hits [50.03%]
129974492 LLC-loads # 3.038 M/sec
[40.07%]
56701883 LLC-load-misses # 43.63% of all LL-cache
hits [40.08%]
3.410231367 seconds time elapsed
The patched version even runs a bit faster.
Perf annotation shows that 92% time is spent in the while loop
of rte_distributor_get_pkt.
Anothoer 6% spent in the calculation of match
inside rte_distributor_process.
Also we can see that there is a big amount of LLC load miss, which is
perhaps due to cache conflict
in the while-loop of rte_distributor_get_pkt?
I'm no going to draw any conclusion here but evidently the
in_flight_bitmask is not in the hot path, and
is irrelevant to the performance of distributor.
Thanks a lot for your code review and ack.
thx &
rgds,
-qinglai
On Mon, Nov 10, 2014 at 6:55 PM, Bruce Richardson <
bruce.richardson at intel.com> wrote:
> On Mon, Nov 10, 2014 at 05:52:26PM +0200, jigsaw wrote:
> > Hi Bruce,
> >
> > Sorry I didn't. I will run a performance test tomorrow.
> >
> > thx &
> > rgds,
> > -qinglai
> >
>
> On the assumption that no performance regressions show up...
> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
>
>
> > On Mon, Nov 10, 2014 at 5:13 PM, Bruce Richardson <
> > bruce.richardson at intel.com> wrote:
> >
> > > On Mon, Nov 10, 2014 at 04:44:02PM +0200, Qinglai Xiao wrote:
> > > > With introduction of in_flight_bitmask, the whole 32 bits of tag can
> be
> > > > used. Further more, this patch fixed the integer overflow when
> finding
> > > > the matched tags.
> > > > The maximum number workers is now defined as 64, which is length of
> > > > double-word. The link between number of workers and RTE_MAX_LCORE is
> > > > now removed. Compile time check is added to ensure the
> > > > RTE_DISTRIB_MAX_WORKERS is less than or equal to size of double-word.
> > > >
> > > > Signed-off-by: Qinglai Xiao <jigsaw at gmail.com>
> > >
> > > Looks good to me.
> > > Just before I ack this, have you checked to see if there is any
> > > performance impact?
> > >
> > > /Bruce
> > >
> > > > ---
> > > > lib/librte_distributor/rte_distributor.c | 64
> > > ++++++++++++++++++++++--------
> > > > lib/librte_distributor/rte_distributor.h | 4 ++
> > > > 2 files changed, 51 insertions(+), 17 deletions(-)
> > > >
> > > > diff --git a/lib/librte_distributor/rte_distributor.c
> > > b/lib/librte_distributor/rte_distributor.c
> > > > index 3dfec4a..2c5d61c 100644
> > > > --- a/lib/librte_distributor/rte_distributor.c
> > > > +++ b/lib/librte_distributor/rte_distributor.c
> > > > @@ -62,6 +62,13 @@
> > > > #define RTE_DISTRIB_RETURNS_MASK (RTE_DISTRIB_MAX_RETURNS - 1)
> > > >
> > > > /**
> > > > + * Maximum number of workers allowed.
> > > > + * Be aware of increasing the limit, becaus it is limited by how we
> > > track
> > > > + * in-flight tags. See @in_flight_bitmask and
> @rte_distributor_process
> > > > + */
> > > > +#define RTE_DISTRIB_MAX_WORKERS 64
> > > > +
> > > > +/**
> > > > * Buffer structure used to pass the pointer data between cores.
> This
> > > is cache
> > > > * line aligned, but to improve performance and prevent adjacent
> > > cache-line
> > > > * prefetches of buffers for other workers, e.g. when worker 1's
> buffer
> > > is on
> > > > @@ -91,11 +98,17 @@ struct rte_distributor {
> > > > char name[RTE_DISTRIBUTOR_NAMESIZE]; /**< Name of the ring. */
> > > > unsigned num_workers; /**< Number of workers
> > > polling */
> > > >
> > > > - uint32_t in_flight_tags[RTE_MAX_LCORE];
> > > > - /**< Tracks the tag being processed per core, 0 == no
> pkt
> > > */
> > > > - struct rte_distributor_backlog backlog[RTE_MAX_LCORE];
> > > > + uint32_t in_flight_tags[RTE_DISTRIB_MAX_WORKERS];
> > > > + /**< Tracks the tag being processed per core */
> > > > + uint64_t in_flight_bitmask;
> > > > + /**< on/off bits for in-flight tags.
> > > > + * Note that if RTE_DISTRIB_MAX_WORKERS is larger than
> 64
> > > then
> > > > + * the bitmask has to expand.
> > > > + */
> > > > +
> > > > + struct rte_distributor_backlog
> backlog[RTE_DISTRIB_MAX_WORKERS];
> > > >
> > > > - union rte_distributor_buffer bufs[RTE_MAX_LCORE];
> > > > + union rte_distributor_buffer bufs[RTE_DISTRIB_MAX_WORKERS];
> > > >
> > > > struct rte_distributor_returned_pkts returns;
> > > > };
> > > > @@ -189,6 +202,7 @@ static inline void
> > > > handle_worker_shutdown(struct rte_distributor *d, unsigned wkr)
> > > > {
> > > > d->in_flight_tags[wkr] = 0;
> > > > + d->in_flight_bitmask &= ~(1UL << wkr);
> > > > d->bufs[wkr].bufptr64 = 0;
> > > > if (unlikely(d->backlog[wkr].count != 0)) {
> > > > /* On return of a packet, we need to move the
> > > > @@ -211,7 +225,10 @@ handle_worker_shutdown(struct rte_distributor
> *d,
> > > unsigned wkr)
> > > > pkts[i] = (void *)((uintptr_t)(bl->pkts[idx] >>
> > > > RTE_DISTRIB_FLAG_BITS));
> > > > }
> > > > - /* recursive call */
> > > > + /* recursive call.
> > > > + * Note that the tags were set before first level call
> > > > + * to rte_distributor_process.
> > > > + */
> > > > rte_distributor_process(d, pkts, i);
> > > > bl->count = bl->start = 0;
> > > > }
> > > > @@ -242,6 +259,7 @@ process_returns(struct rte_distributor *d)
> > > > else {
> > > > d->bufs[wkr].bufptr64 =
> > > RTE_DISTRIB_GET_BUF;
> > > > d->in_flight_tags[wkr] = 0;
> > > > + d->in_flight_bitmask &= ~(1UL << wkr);
> > > > }
> > > > oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
> > > > } else if (data & RTE_DISTRIB_RETURN_BUF) {
> > > > @@ -284,14 +302,18 @@ rte_distributor_process(struct rte_distributor
> *d,
> > > > next_value = (((int64_t)(uintptr_t)next_mb)
> > > > << RTE_DISTRIB_FLAG_BITS);
> > > > /*
> > > > - * Set the low bit on the tag, so we can
> guarantee
> > > that
> > > > - * we never store a tag value of zero. That
> means
> > > we can
> > > > - * use the zero-value to indicate that no
> packet is
> > > > - * being processed by a worker.
> > > > + * User is advocated to set tag vaue for each
> > > > + * mbuf before calling rte_distributor_process.
> > > > + * User defined tags are used to identify
> flows,
> > > > + * or sessions.
> > > > */
> > > > - new_tag = (next_mb->hash.usr | 1);
> > > > + new_tag = next_mb->hash.usr;
> > > >
> > > > - uint32_t match = 0;
> > > > + /*
> > > > + * Note that if RTE_DISTRIB_MAX_WORKERS is
> larger
> > > than 64
> > > > + * then the size of match has to be expanded.
> > > > + */
> > > > + uint64_t match = 0;
> > > > unsigned i;
> > > > /*
> > > > * to scan for a match use "xor" and "not" to
> get
> > > a 0/1
> > > > @@ -303,9 +325,12 @@ rte_distributor_process(struct rte_distributor
> *d,
> > > > match |= (!(d->in_flight_tags[i] ^
> new_tag)
> > > > << i);
> > > >
> > > > + /* Only turned-on bits are considered as match
> */
> > > > + match &= d->in_flight_bitmask;
> > > > +
> > > > if (match) {
> > > > next_mb = NULL;
> > > > - unsigned worker = __builtin_ctz(match);
> > > > + unsigned worker =
> __builtin_ctzl(match);
> > > > if (add_to_backlog(&d->backlog[worker],
> > > > next_value) < 0)
> > > > next_idx--;
> > > > @@ -322,6 +347,7 @@ rte_distributor_process(struct rte_distributor
> *d,
> > > > else {
> > > > d->bufs[wkr].bufptr64 = next_value;
> > > > d->in_flight_tags[wkr] = new_tag;
> > > > + d->in_flight_bitmask |= (1UL << wkr);
> > > > next_mb = NULL;
> > > > }
> > > > oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
> > > > @@ -379,11 +405,13 @@ rte_distributor_returned_pkts(struct
> > > rte_distributor *d,
> > > > static inline unsigned
> > > > total_outstanding(const struct rte_distributor *d)
> > > > {
> > > > - unsigned wkr, total_outstanding = 0;
> > > > + unsigned wkr, total_outstanding;
> > > > +
> > > > + total_outstanding = __builtin_popcountl(d->in_flight_bitmask);
> > > >
> > > > for (wkr = 0; wkr < d->num_workers; wkr++)
> > > > - total_outstanding += d->backlog[wkr].count +
> > > > - !!(d->in_flight_tags[wkr]);
> > > > + total_outstanding += d->backlog[wkr].count;
> > > > +
> > > > return total_outstanding;
> > > > }
> > > >
> > > > @@ -423,9 +451,11 @@ rte_distributor_create(const char *name,
> > > >
> > > > /* compilation-time checks */
> > > > RTE_BUILD_BUG_ON((sizeof(*d) & CACHE_LINE_MASK) != 0);
> > > > - RTE_BUILD_BUG_ON((RTE_MAX_LCORE & 7) != 0);
> > > > + RTE_BUILD_BUG_ON((RTE_DISTRIB_MAX_WORKERS & 7) != 0);
> > > > + RTE_BUILD_BUG_ON(RTE_DISTRIB_MAX_WORKERS >
> > > > + sizeof(d->in_flight_bitmask) *
> CHAR_BIT);
> > > >
> > > > - if (name == NULL || num_workers >= RTE_MAX_LCORE) {
> > > > + if (name == NULL || num_workers >= RTE_DISTRIB_MAX_WORKERS) {
> > > > rte_errno = EINVAL;
> > > > return NULL;
> > > > }
> > > > diff --git a/lib/librte_distributor/rte_distributor.h
> > > b/lib/librte_distributor/rte_distributor.h
> > > > index ec0d74a..cc1d559 100644
> > > > --- a/lib/librte_distributor/rte_distributor.h
> > > > +++ b/lib/librte_distributor/rte_distributor.h
> > > > @@ -88,6 +88,10 @@ rte_distributor_create(const char *name, unsigned
> > > socket_id,
> > > > * packets. The distributor will ensure that no two packets that
> have
> > > the
> > > > * same flow id, or tag, in the mbuf will be procesed at the same
> time.
> > > > *
> > > > + * The user is advocated to set tag for each mbuf before calling
> this
> > > function.
> > > > + * If user doesn't set the tag, the tag value can be various values
> > > depending on
> > > > + * driver implementation and configuration.
> > > > + *
> > > > * This is not multi-thread safe and should only be called on a
> single
> > > lcore.
> > > > *
> > > > * @param d
> > > > --
> > > > 1.7.1
> > > >
> > >
>
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