Adding Paul for feedback
> -----Original Message-----
> From: Ruifeng Wang <ruifeng.w...@arm.com>
> Sent: Friday, September 6, 2019 4:46 AM
> To: bruce.richard...@intel.com; vladimir.medved...@intel.com;
> olivier.m...@6wind.com
> Cc: dev@dpdk.org; step...@networkplumber.org;
> konstantin.anan...@intel.com; Gavin Hu (Arm Technology China)
> <gavin...@arm.com>; Honnappa Nagarahalli
> <honnappa.nagaraha...@arm.com>; Dharmik Thakkar
> <dharmik.thak...@arm.com>; nd <n...@arm.com>; Ruifeng Wang (Arm
> Technology China) <ruifeng.w...@arm.com>
> Subject: [PATCH v2 3/6] lib/lpm: integrate RCU QSBR
>
> Currently, the tbl8 group is freed even though the readers might be using the
> tbl8 group entries. The freed tbl8 group can be reallocated quickly. This
> results
> in incorrect lookup results.
>
> RCU QSBR process is integrated for safe tbl8 group reclaim.
> Refer to RCU documentation to understand various aspects of integrating RCU
> library into other libraries.
>
> Signed-off-by: Ruifeng Wang <ruifeng.w...@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> ---
> lib/librte_lpm/Makefile | 3 +-
> lib/librte_lpm/meson.build | 2 +
> lib/librte_lpm/rte_lpm.c | 223 +++++++++++++++++++++++++++--
> lib/librte_lpm/rte_lpm.h | 22 +++
> lib/librte_lpm/rte_lpm_version.map | 6 +
> lib/meson.build | 3 +-
> 6 files changed, 244 insertions(+), 15 deletions(-)
>
> diff --git a/lib/librte_lpm/Makefile b/lib/librte_lpm/Makefile index
> a7946a1c5..ca9e16312 100644
> --- a/lib/librte_lpm/Makefile
> +++ b/lib/librte_lpm/Makefile
> @@ -6,9 +6,10 @@ include $(RTE_SDK)/mk/rte.vars.mk # library name LIB =
> librte_lpm.a
>
> +CFLAGS += -DALLOW_EXPERIMENTAL_API
> CFLAGS += -O3
> CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR)
> -LDLIBS += -lrte_eal -lrte_hash
> +LDLIBS += -lrte_eal -lrte_hash -lrte_rcu
>
> EXPORT_MAP := rte_lpm_version.map
>
> diff --git a/lib/librte_lpm/meson.build b/lib/librte_lpm/meson.build index
> a5176d8ae..19a35107f 100644
> --- a/lib/librte_lpm/meson.build
> +++ b/lib/librte_lpm/meson.build
> @@ -2,9 +2,11 @@
> # Copyright(c) 2017 Intel Corporation
>
> version = 2
> +allow_experimental_apis = true
> sources = files('rte_lpm.c', 'rte_lpm6.c') headers = files('rte_lpm.h',
> 'rte_lpm6.h') # since header files have different names, we can install all
> vector
> headers # without worrying about which architecture we actually need
> headers += files('rte_lpm_altivec.h', 'rte_lpm_neon.h', 'rte_lpm_sse.h')
> deps +=
> ['hash']
> +deps += ['rcu']
> diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c index
> 3a929a1b1..9764b8de6 100644
> --- a/lib/librte_lpm/rte_lpm.c
> +++ b/lib/librte_lpm/rte_lpm.c
> @@ -1,5 +1,6 @@
> /* SPDX-License-Identifier: BSD-3-Clause
> * Copyright(c) 2010-2014 Intel Corporation
> + * Copyright(c) 2019 Arm Limited
> */
>
> #include <string.h>
> @@ -22,6 +23,7 @@
> #include <rte_rwlock.h>
> #include <rte_spinlock.h>
> #include <rte_tailq.h>
> +#include <rte_ring.h>
>
> #include "rte_lpm.h"
>
> @@ -39,6 +41,11 @@ enum valid_flag {
> VALID
> };
>
> +struct __rte_lpm_qs_item {
> + uint64_t token; /**< QSBR token.*/
> + uint32_t index; /**< tbl8 group index.*/
> +};
> +
> /* Macro to enable/disable run-time checks. */ #if
> defined(RTE_LIBRTE_LPM_DEBUG) #include <rte_debug.h> @@ -381,6
> +388,7 @@ rte_lpm_free_v1604(struct rte_lpm *lpm)
>
> rte_mcfg_tailq_write_unlock();
>
> + rte_ring_free(lpm->qs_fifo);
> rte_free(lpm->tbl8);
> rte_free(lpm->rules_tbl);
> rte_free(lpm);
> @@ -390,6 +398,147 @@ BIND_DEFAULT_SYMBOL(rte_lpm_free, _v1604,
> 16.04); MAP_STATIC_SYMBOL(void rte_lpm_free(struct rte_lpm *lpm),
> rte_lpm_free_v1604);
>
> +/* Add an item into FIFO.
> + * return: 0 - success
> + */
> +static int
> +__rte_lpm_rcu_qsbr_fifo_push(struct rte_ring *fifo,
> + struct __rte_lpm_qs_item *item)
> +{
> + if (rte_ring_free_count(fifo) < 2) {
> + RTE_LOG(ERR, LPM, "QS FIFO full\n");
> + rte_errno = ENOSPC;
> + return 1;
> + }
> +
> + (void)rte_ring_sp_enqueue(fifo, (void *)(uintptr_t)item->token);
> + (void)rte_ring_sp_enqueue(fifo, (void *)(uintptr_t)item->index);
> +
> + return 0;
> +}
> +
> +/* Remove item from FIFO.
> + * Used when data observed by rte_ring_peek.
> + */
> +static void
> +__rte_lpm_rcu_qsbr_fifo_pop(struct rte_ring *fifo,
> + struct __rte_lpm_qs_item *item)
> +{
> + void *obj_token = NULL;
> + void *obj_index = NULL;
> +
> + (void)rte_ring_sc_dequeue(fifo, &obj_token);
> + (void)rte_ring_sc_dequeue(fifo, &obj_index);
> +
> + if (item) {
> + item->token = (uint64_t)((uintptr_t)obj_token);
> + item->index = (uint32_t)((uintptr_t)obj_index);
> + }
> +}
> +
> +/* Max number of tbl8 groups to reclaim at one time. */
> +#define RCU_QSBR_RECLAIM_SIZE 8
> +
> +/* When RCU QSBR FIFO usage is above 1/(2^RCU_QSBR_RECLAIM_LEVEL),
> + * reclaim will be triggered by tbl8_free.
> + */
> +#define RCU_QSBR_RECLAIM_LEVEL 3
> +
> +/* Reclaim some tbl8 groups based on quiescent state check.
> + * RCU_QSBR_RECLAIM_SIZE groups will be reclaimed at max.
> + * Params: lpm - lpm object handle
> + * index - (onput) one of successfully reclaimed tbl8 groups
> + * return: 0 - success, 1 - no group reclaimed.
> + */
> +static uint32_t
> +__rte_lpm_rcu_qsbr_reclaim_chunk(struct rte_lpm *lpm, uint32_t *index)
> +{
> + struct __rte_lpm_qs_item qs_item;
> + struct rte_lpm_tbl_entry *tbl8_entry = NULL;
> + void *obj_token;
> + uint32_t cnt = 0;
> +
> + RTE_LOG(DEBUG, LPM, "RCU QSBR reclaimation triggered.\n");
> + /* Check reader threads quiescent state and
> + * reclaim as much tbl8 groups as possible.
> + */
> + while ((cnt < RCU_QSBR_RECLAIM_SIZE) &&
> + (rte_ring_peek(lpm->qs_fifo, &obj_token) == 0) &&
> + (rte_rcu_qsbr_check(lpm->qsv,
> (uint64_t)((uintptr_t)obj_token),
> + false) == 1)) {
> + __rte_lpm_rcu_qsbr_fifo_pop(lpm->qs_fifo, &qs_item);
> +
> + tbl8_entry = &lpm->tbl8[qs_item.index *
> +
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
> + memset(&tbl8_entry[0], 0,
> + RTE_LPM_TBL8_GROUP_NUM_ENTRIES *
> + sizeof(tbl8_entry[0]));
> + cnt++;
> + }
> +
> + RTE_LOG(DEBUG, LPM, "RCU QSBR reclaimed %u groups.\n", cnt);
> + if (cnt) {
> + if (index)
> + *index = qs_item.index;
> + return 0;
> + }
> + return 1;
> +}
> +
> +/* Trigger tbl8 group reclaim when necessary.
> + * Reclaim happens when RCU QSBR queue usage
> + * is over 1/(2^RCU_QSBR_RECLAIM_LEVEL).
> + */
> +static void
> +__rte_lpm_rcu_qsbr_try_reclaim(struct rte_lpm *lpm) {
> + if (lpm->qsv == NULL)
> + return;
> +
> + if (rte_ring_count(lpm->qs_fifo) <
> + (rte_ring_get_capacity(lpm->qs_fifo) >>
> RCU_QSBR_RECLAIM_LEVEL))
> + return;
> +
> + (void)__rte_lpm_rcu_qsbr_reclaim_chunk(lpm, NULL); }
> +
> +/* Associate QSBR variable with an LPM object.
> + */
> +int
> +rte_lpm_rcu_qsbr_add(struct rte_lpm *lpm, struct rte_rcu_qsbr *v) {
> + uint32_t qs_fifo_size;
> + char rcu_ring_name[RTE_RING_NAMESIZE];
> +
> + if ((lpm == NULL) || (v == NULL)) {
> + rte_errno = EINVAL;
> + return 1;
> + }
> +
> + if (lpm->qsv) {
> + rte_errno = EEXIST;
> + return 1;
> + }
> +
> + /* round up qs_fifo_size to next power of two that is not less than
> + * number_tbl8s. Will store 'token' and 'index'.
> + */
> + qs_fifo_size = rte_align32pow2((2 * lpm->number_tbl8s) + 1);
> +
> + /* Init QSBR reclaiming FIFO. */
> + snprintf(rcu_ring_name, sizeof(rcu_ring_name), "LPM_RCU_%s", lpm-
> >name);
> + lpm->qs_fifo = rte_ring_create(rcu_ring_name, qs_fifo_size,
> + SOCKET_ID_ANY, 0);
> + if (lpm->qs_fifo == NULL) {
> + RTE_LOG(ERR, LPM, "LPM QS FIFO memory allocation
> failed\n");
> + rte_errno = ENOMEM;
> + return 1;
> + }
> + lpm->qsv = v;
> +
> + return 0;
> +}
> +
> /*
> * Adds a rule to the rule table.
> *
> @@ -640,6 +789,35 @@ rule_find_v1604(struct rte_lpm *lpm, uint32_t
> ip_masked, uint8_t depth)
> return -EINVAL;
> }
>
> +static int32_t
> +tbl8_alloc_reclaimed(struct rte_lpm *lpm) {
> + struct rte_lpm_tbl_entry *tbl8_entry = NULL;
> + uint32_t index;
> +
> + if (lpm->qsv != NULL) {
> + if (__rte_lpm_rcu_qsbr_reclaim_chunk(lpm, &index) == 0) {
> + /* Set the last reclaimed tbl8 group as VALID. */
> + struct rte_lpm_tbl_entry new_tbl8_entry = {
> + .next_hop = 0,
> + .valid = INVALID,
> + .depth = 0,
> + .valid_group = VALID,
> + };
> +
> + tbl8_entry = &lpm->tbl8[index *
> +
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
> + __atomic_store(tbl8_entry, &new_tbl8_entry,
> + __ATOMIC_RELAXED);
> +
> + /* Return group index for reclaimed tbl8 group. */
> + return index;
> + }
> + }
> +
> + return -ENOSPC;
> +}
> +
> /*
> * Find, clean and allocate a tbl8.
> */
> @@ -679,14 +857,15 @@ tbl8_alloc_v20(struct rte_lpm_tbl_entry_v20
> *tbl8) }
>
> static int32_t
> -tbl8_alloc_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t number_tbl8s)
> +tbl8_alloc_v1604(struct rte_lpm *lpm)
> {
> uint32_t group_idx; /* tbl8 group index. */
> struct rte_lpm_tbl_entry *tbl8_entry;
>
> /* Scan through tbl8 to find a free (i.e. INVALID) tbl8 group. */
> - for (group_idx = 0; group_idx < number_tbl8s; group_idx++) {
> - tbl8_entry = &tbl8[group_idx *
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
> + for (group_idx = 0; group_idx < lpm->number_tbl8s; group_idx++) {
> + tbl8_entry = &lpm->tbl8[group_idx *
> +
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
> /* If a free tbl8 group is found clean it and set as VALID. */
> if (!tbl8_entry->valid_group) {
> struct rte_lpm_tbl_entry new_tbl8_entry = { @@ -
> 708,8 +887,8 @@ tbl8_alloc_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t
> number_tbl8s)
> }
> }
>
> - /* If there are no tbl8 groups free then return error. */
> - return -ENOSPC;
> + /* If there are no tbl8 groups free then check reclaim queue. */
> + return tbl8_alloc_reclaimed(lpm);
> }
>
> static void
> @@ -728,13 +907,31 @@ tbl8_free_v20(struct rte_lpm_tbl_entry_v20 *tbl8,
> uint32_t tbl8_group_start) }
>
> static void
> -tbl8_free_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t tbl8_group_start)
> +tbl8_free_v1604(struct rte_lpm *lpm, uint32_t tbl8_group_start)
> {
> - /* Set tbl8 group invalid*/
> + struct __rte_lpm_qs_item qs_item;
> struct rte_lpm_tbl_entry zero_tbl8_entry = {0};
>
> - __atomic_store(&tbl8[tbl8_group_start], &zero_tbl8_entry,
> - __ATOMIC_RELAXED);
> + if (lpm->qsv != NULL) {
> + /* Push into QSBR FIFO. */
> + qs_item.token = rte_rcu_qsbr_start(lpm->qsv);
> + qs_item.index =
> + tbl8_group_start /
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES;
> + if (__rte_lpm_rcu_qsbr_fifo_push(lpm->qs_fifo, &qs_item) != 0)
> + /* This should never happen as FIFO size is big enough
> + * to hold all tbl8 groups.
> + */
> + RTE_LOG(ERR, LPM, "Failed to push QSBR FIFO\n");
> +
> + /* Speculatively reclaim tbl8 groups.
> + * Help spread the reclaim work load across multiple calls.
> + */
> + __rte_lpm_rcu_qsbr_try_reclaim(lpm);
> + } else {
> + /* Set tbl8 group invalid*/
> + __atomic_store(&lpm->tbl8[tbl8_group_start],
> &zero_tbl8_entry,
> + __ATOMIC_RELAXED);
> + }
> }
>
> static __rte_noinline int32_t
> @@ -1037,7 +1234,7 @@ add_depth_big_v1604(struct rte_lpm *lpm,
> uint32_t ip_masked, uint8_t depth,
>
> if (!lpm->tbl24[tbl24_index].valid) {
> /* Search for a free tbl8 group. */
> - tbl8_group_index = tbl8_alloc_v1604(lpm->tbl8, lpm-
> >number_tbl8s);
> + tbl8_group_index = tbl8_alloc_v1604(lpm);
>
> /* Check tbl8 allocation was successful. */
> if (tbl8_group_index < 0) {
> @@ -1083,7 +1280,7 @@ add_depth_big_v1604(struct rte_lpm *lpm,
> uint32_t ip_masked, uint8_t depth,
> } /* If valid entry but not extended calculate the index into Table8. */
> else if (lpm->tbl24[tbl24_index].valid_group == 0) {
> /* Search for free tbl8 group. */
> - tbl8_group_index = tbl8_alloc_v1604(lpm->tbl8, lpm-
> >number_tbl8s);
> + tbl8_group_index = tbl8_alloc_v1604(lpm);
>
> if (tbl8_group_index < 0) {
> return tbl8_group_index;
> @@ -1818,7 +2015,7 @@ delete_depth_big_v1604(struct rte_lpm *lpm,
> uint32_t ip_masked,
> */
> lpm->tbl24[tbl24_index].valid = 0;
> __atomic_thread_fence(__ATOMIC_RELEASE);
> - tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
> + tbl8_free_v1604(lpm, tbl8_group_start);
> } else if (tbl8_recycle_index > -1) {
> /* Update tbl24 entry. */
> struct rte_lpm_tbl_entry new_tbl24_entry = { @@ -1834,7
> +2031,7 @@ delete_depth_big_v1604(struct rte_lpm *lpm, uint32_t
> ip_masked,
> __atomic_store(&lpm->tbl24[tbl24_index], &new_tbl24_entry,
> __ATOMIC_RELAXED);
> __atomic_thread_fence(__ATOMIC_RELEASE);
> - tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
> + tbl8_free_v1604(lpm, tbl8_group_start);
> }
> #undef group_idx
> return 0;
> diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h index
> 906ec4483..5079fb262 100644
> --- a/lib/librte_lpm/rte_lpm.h
> +++ b/lib/librte_lpm/rte_lpm.h
> @@ -1,5 +1,6 @@
> /* SPDX-License-Identifier: BSD-3-Clause
> * Copyright(c) 2010-2014 Intel Corporation
> + * Copyright(c) 2019 Arm Limited
> */
>
> #ifndef _RTE_LPM_H_
> @@ -21,6 +22,7 @@
> #include <rte_common.h>
> #include <rte_vect.h>
> #include <rte_compat.h>
> +#include <rte_rcu_qsbr.h>
>
> #ifdef __cplusplus
> extern "C" {
> @@ -186,6 +188,8 @@ struct rte_lpm {
> __rte_cache_aligned; /**< LPM tbl24 table. */
> struct rte_lpm_tbl_entry *tbl8; /**< LPM tbl8 table. */
> struct rte_lpm_rule *rules_tbl; /**< LPM rules. */
> + struct rte_rcu_qsbr *qsv; /**< RCU QSBR variable for tbl8
> group.*/
> + struct rte_ring *qs_fifo; /**< RCU QSBR reclaiming queue. */
> };
>
> /**
> @@ -248,6 +252,24 @@ rte_lpm_free_v20(struct rte_lpm_v20 *lpm); void
> rte_lpm_free_v1604(struct rte_lpm *lpm);
>
> +/**
> + * Associate RCU QSBR variable with an LPM object.
> + *
> + * @param lpm
> + * the lpm object to add RCU QSBR
> + * @param v
> + * RCU QSBR variable
> + * @return
> + * On success - 0
> + * On error - 1 with error code set in rte_errno.
> + * Possible rte_errno codes are:
> + * - EINVAL - invalid pointer
> + * - EEXIST - already added QSBR
> + * - ENOMEM - memory allocation failure
> + */
> +__rte_experimental
> +int rte_lpm_rcu_qsbr_add(struct rte_lpm *lpm, struct rte_rcu_qsbr *v);
> +
> /**
> * Add a rule to the LPM table.
> *
> diff --git a/lib/librte_lpm/rte_lpm_version.map
> b/lib/librte_lpm/rte_lpm_version.map
> index 90beac853..b353aabd2 100644
> --- a/lib/librte_lpm/rte_lpm_version.map
> +++ b/lib/librte_lpm/rte_lpm_version.map
> @@ -44,3 +44,9 @@ DPDK_17.05 {
> rte_lpm6_lookup_bulk_func;
>
> } DPDK_16.04;
> +
> +EXPERIMENTAL {
> + global:
> +
> + rte_lpm_rcu_qsbr_add;
> +};
> diff --git a/lib/meson.build b/lib/meson.build index e5ff83893..3a96f005d
> 100644
> --- a/lib/meson.build
> +++ b/lib/meson.build
> @@ -11,6 +11,7 @@
> libraries = [
> 'kvargs', # eal depends on kvargs
> 'eal', # everything depends on eal
> + 'rcu', # hash and lpm depends on this
> 'ring', 'mempool', 'mbuf', 'net', 'meter', 'ethdev', 'pci', # core
> 'cmdline',
> 'metrics', # bitrate/latency stats depends on this @@ -22,7 +23,7 @@
> libraries = [
> 'gro', 'gso', 'ip_frag', 'jobstats',
> 'kni', 'latencystats', 'lpm', 'member',
> 'power', 'pdump', 'rawdev',
> - 'rcu', 'reorder', 'sched', 'security', 'stack', 'vhost',
> + 'reorder', 'sched', 'security', 'stack', 'vhost',
> # ipsec lib depends on net, crypto and security
> 'ipsec',
> # add pkt framework libs which use other libs from above
> --
> 2.17.1
