From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f42.google.com (mail-pl0-f42.google.com [209.85.160.42]) by dpdk.org (Postfix) with ESMTP id E62F91B3B0 for ; Wed, 8 Nov 2017 03:31:54 +0100 (CET) Received: by mail-pl0-f42.google.com with SMTP id 14so322476plf.4 for ; Tue, 07 Nov 2017 18:31:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding; bh=b0fnuo9XQl819hwHnUFipQqXmrXJnkjGV4BnXuXsFyE=; b=chvDyU5yxptX1CaSimO22JpH9IUeCFzIUTTHFA4CMfnoRw3ku0Ufe5zC/5LpvssZM7 QPJd+qaHiYR6YnAbIDQXLFEeDN49sFWNyE2n8EOMFsOIq6e3Cj4fVNL5GIg7L3PMlVVO XhA7/JVwTdqAJ4zW8d/J3N4dXpBuf5qHFYQaink+2d14S6kzR84HhS0C++Wh7212oAY4 h4UFTCduIaBsXY/iMvNHhl1lk4QGiNj5Kzd+L5/M223y2ATEN6BApcgFkXB9/kmau+Sw dKDM78+CtnnQI9P3WVUzCLhkja0mTu3y9coe9SfNGekzWUXyc+uSDRFQUWva6kHl0kMa GjJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding; bh=b0fnuo9XQl819hwHnUFipQqXmrXJnkjGV4BnXuXsFyE=; b=Oakk62iokB8vnY7MZsHuSKlVBHQ0XWjHG7GYTGhIO7t6lT/rgUof1izuBUaFOvtvOg WQrOxAym3AFLydr1+qWiPs6Z8ahdp7Zify4pxhZS5GZ70pODQs53WSG/NUu6xD4vOe3q X8bgIZdAsr4Q/z775CFUtZrRTvb0ajiVk3NRs1LAtuTxz4o7MT8wQKnD85Ovfs56ceJ5 4VB15AQ4HhgRwlBacQdgDPIMpkF7ob1dPx27w4A4Vs2aJvCKzDrE0+9JEdnKhndM20Ny oERGjAObXsAD0KL2/4I/lZREYI7iy/jRUIIjy2PDyMVXD5N0dcUMaCtDTYZuz6rHrmoI Zf7A== X-Gm-Message-State: AJaThX5OWcepKFXdo2iZiKYZAerX5aNlImgCxXjqySGbUYO1DNw/uIWR 8cMWLNa5z60poG72K5UesIk= X-Google-Smtp-Source: ABhQp+Q00ExGJdKf605abhmeSXREaUWeFu8tTx6/JAiECdYiNhatNwMyB9k7fPOcHDIE5CkmqgBYcg== X-Received: by 10.84.224.76 with SMTP id a12mr727655plt.207.1510108313975; Tue, 07 Nov 2017 18:31:53 -0800 (PST) Received: from [0.0.0.0] (67.209.179.165.16clouds.com. [67.209.179.165]) by smtp.gmail.com with ESMTPSA id u6sm5441236pfg.175.2017.11.07.18.31.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Nov 2017 18:31:53 -0800 (PST) To: Jerin Jacob Cc: dev@dpdk.org, olivier.matz@6wind.com, konstantin.ananyev@intel.com, bruce.richardson@intel.com, jianbo.liu@arm.com, hemant.agrawal@nxp.com, jie2.liu@hxt-semitech.com, bing.zhao@hxt-semitech.com, jia.he@hxt-semitech.com References: <1509612210-5499-1-git-send-email-hejianet@gmail.com> <20171102172337.GB1478@jerin> <25192429-8369-ac3d-44b0-c1b1d7182ef0@gmail.com> <20171103125616.GB20326@jerin> <7b7f3677-8313-9a2f-868f-b3a6231548d6@gmail.com> <20171107043655.GA3244@jerin> <20171107095727.GA23010@jerin> From: Jia He Message-ID: <06fb4de9-5348-01e2-f9bb-1aecb90c6adc@gmail.com> Date: Wed, 8 Nov 2017 10:31:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171107095727.GA23010@jerin> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH v2] ring: guarantee ordering of cons/prod loading when doing X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Nov 2017 02:31:55 -0000 Hi Jerin Thank you, I mistakenly think x86 doen't need rte_smp_rmb(). Since rte_smp_rmb() only impact x86's compiler optimization, I will simplify the codes as your suggestions Cheers, Jia On 11/7/2017 5:57 PM, Jerin Jacob Wrote: > -----Original Message----- >> Date: Tue, 7 Nov 2017 16:34:30 +0800 >> From: Jia He >> To: Jerin Jacob >> Cc: dev@dpdk.org, olivier.matz@6wind.com, konstantin.ananyev@intel.com, >> bruce.richardson@intel.com, jianbo.liu@arm.com, hemant.agrawal@nxp.com, >> jie2.liu@hxt-semitech.com, bing.zhao@hxt-semitech.com, >> jia.he@hxt-semitech.com >> Subject: Re: [PATCH v2] ring: guarantee ordering of cons/prod loading when >> doing >> User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 >> Thunderbird/52.4.0 >> >> >> >> On 11/7/2017 12:36 PM, Jerin Jacob Wrote: >>> -----Original Message----- >>> >>> On option could be to change the prototype of update_tail() and make >>> compiler accommodate it for zero cost for arm64(Which I think, it it the >>> case. But you can check the generated instructions) >>> If not, move, __rte_ring_do_dequeue() and __rte_ring_do_enqueue() instead of >>> __rte_ring_move_prod_head/__rte_ring_move_cons_head/update_tail() >>> >>> >>> ➜ [master][dpdk.org] $ git diff >>> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h >>> index 5e9b3b7b4..b32648825 100644 >>> --- a/lib/librte_ring/rte_ring.h >>> +++ b/lib/librte_ring/rte_ring.h >>> @@ -358,8 +358,12 @@ void rte_ring_dump(FILE *f, const struct rte_ring >>> *r); >>> static __rte_always_inline void >>> update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t >>> new_val, >>> - uint32_t single) >>> + uint32_t single, const uint32_t enqueue) >>> { >>> + if (enqueue) >>> + rte_smp_wmb(); >>> + else >>> + rte_smp_rmb(); >>> /* >>> * If there are other enqueues/dequeues in progress that >>> * preceded us, >>> * we need to wait for them to complete >>> @@ -470,9 +474,8 @@ __rte_ring_do_enqueue(struct rte_ring *r, void * >>> const *obj_table, >>> goto end; >>> ENQUEUE_PTRS(r, &r[1], prod_head, obj_table, n, void *); >>> - rte_smp_wmb(); >>> - update_tail(&r->prod, prod_head, prod_next, is_sp); >>> + update_tail(&r->prod, prod_head, prod_next, is_sp, 1); >>> end: >>> if (free_space != NULL) >>> *free_space = free_entries - n; >>> @@ -575,9 +578,8 @@ __rte_ring_do_dequeue(struct rte_ring *r, void >>> **obj_table, >>> goto end; >>> DEQUEUE_PTRS(r, &r[1], cons_head, obj_table, n, void *); >>> - rte_smp_rmb(); >>> - update_tail(&r->cons, cons_head, cons_next, is_sc); >>> + update_tail(&r->cons, cons_head, cons_next, is_sc, 0); >>> end: >>> if (available != NULL) >>> >>> >>> >> Hi Jerin, yes I knew this suggestion in update_tail. >> But what I mean is the rte_smp_rmb() in __rte_ring_move_cons_head and >> __rte_ring_move_pros_head: >> [option 1] >> +        *old_head = r->cons.head; >> +        rte_smp_rmb(); >> +        const uint32_t prod_tail = r->prod.tail; >> >> [option 2] >> +        *old_head = __atomic_load_n(&r->cons.head, >> +                    __ATOMIC_ACQUIRE); >> +        *old_head = r->cons.head; >> >> ie.I wonder what is the suitable new config name to distinguish the above 2 >> options? > Why? > If you fix the generic version with rte_smp_rmb() then we just need only > one config to differentiate between c11 vs generic. See comments below, > >> Thanks for the patience :-) >> >> see my drafted patch below, the marcro "PREFER": >> + */ >> + >> +#ifndef _RTE_RING_C11_MEM_H_ >> +#define _RTE_RING_C11_MEM_H_ >> + >> +static __rte_always_inline void >> +update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t >> new_val, >> +        uint32_t single, uint32_t enqueue) >> +{ >> +    /* Don't need wmb/rmb when we prefer to use load_acquire/ >> +     * store_release barrier */ >> +#ifndef PREFER >> +    if (enqueue) >> +        rte_smp_wmb(); >> +    else >> +        rte_smp_rmb(); >> +#endif > You can remove PREFER and let the "generic" version has this. For x86, > rte_smp_?mb() it will be NOOP. So no issue. > >> + >> +    /* >> +     * If there are other enqueues/dequeues in progress that preceded us, >> +     * we need to wait for them to complete >> +     */ >> +    if (!single) >> +        while (unlikely(ht->tail != old_val)) >> +            rte_pause(); >> + >> +#ifdef PREFER >> +    __atomic_store_n(&ht->tail, new_val, __ATOMIC_RELEASE); > for c11 mem model version, it needs only __atomic_store_n version. > >> +#else >> +    ht->tail = new_val; >> +#endif >> +} >> + >> +/** >> + * @internal This function updates the producer head for enqueue >> + * >> + * @param r >> + *   A pointer to the ring structure >> + * @param is_sp >> + *   Indicates whether multi-producer path is needed or not >> + * @param n >> + *   The number of elements we will want to enqueue, i.e. how far should >> the >> + *   head be moved >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Enqueue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Enqueue as many items as possible from ring >> + * @param old_head >> + *   Returns head value as it was before the move, i.e. where enqueue >> starts >> + * @param new_head >> + *   Returns the current/new head value i.e. where enqueue finishes >> + * @param free_entries >> + *   Returns the amount of free space in the ring BEFORE head was moved >> + * @return >> + *   Actual number of objects enqueued. >> + *   If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_move_prod_head(struct rte_ring *r, int is_sp, >> +        unsigned int n, enum rte_ring_queue_behavior behavior, >> +        uint32_t *old_head, uint32_t *new_head, >> +        uint32_t *free_entries) >> +{ >> +    const uint32_t capacity = r->capacity; >> +    unsigned int max = n; >> +    int success; >> + >> +    do { >> +        /* Reset n to the initial burst count */ >> +        n = max; >> + >> +#ifdef PREFER >> +        *old_head = __atomic_load_n(&r->prod.head, >> +                    __ATOMIC_ACQUIRE); >> +#else >> +        *old_head = r->prod.head; >> +        /* prevent reorder of load/load */ >> +        rte_smp_rmb(); >> +#endif > Same as above comment. > >> +        const uint32_t cons_tail = r->cons.tail; >> +        /* >> +         *  The subtraction is done between two unsigned 32bits value >> +         * (the result is always modulo 32 bits even if we have >> +         * *old_head > cons_tail). So 'free_entries' is always between 0 >> +         * and capacity (which is < size). >> +         */ >> +        *free_entries = (capacity + cons_tail - *old_head); >> + >> +        /* check that we have enough room in ring */ >> +        if (unlikely(n > *free_entries)) >> +static __rte_always_inline unsigned int >> +__rte_ring_do_enqueue(struct rte_ring *r, void * const *obj_table, >> +         unsigned int n, enum rte_ring_queue_behavior behavior, >> +         int is_sp, unsigned int *free_space) >> +{ > > Duplicate function, No need to replicate on both versions. > > >> +static __rte_always_inline unsigned int >> +__rte_ring_move_cons_head(struct rte_ring *r, int is_sc, >> +        unsigned int n, enum rte_ring_queue_behavior behavior, >> +        uint32_t *old_head, uint32_t *new_head, >> +        uint32_t *entries) >> +{ >> +    unsigned int max = n; >> +    int success; >> + >> +    /* move cons.head atomically */ >> +    do { >> +        /* Restore n as it may change every loop */ >> +        n = max; >> +#ifdef PREFER >> +        *old_head = __atomic_load_n(&r->cons.head, >> +                    __ATOMIC_ACQUIRE); >> +#else >> +        *old_head = r->cons.head; >> +        /*  prevent reorder of load/load */ >> +        rte_smp_rmb(); >> +#endif > Same as above comment > >> + >> +        const uint32_t prod_tail = r->prod.tail; >> +        /* The subtraction is done between two unsigned 32bits value >> +         * (the result is always modulo 32 bits even if we have >> +         * cons_head > prod_tail). So 'entries' is always between 0 >> +         * and size(ring)-1. */ >> +        *entries = (prod_tail - *old_head); >> + >> +        /* Set the actual entries for dequeue */ >> +        if (n > *entries) >> +            n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries; >> + >> +        if (unlikely(n == 0)) >> +            return 0; >> + >> +        *new_head = *old_head + n; >> +        if (is_sc) >> +            r->cons.head = *new_head, success = 1; >> +        else >> +#ifdef PREFER >> +            success = arch_rte_atomic32_cmpset(&r->cons.head, >> +                            old_head, *new_head, >> +                            0, __ATOMIC_ACQUIRE, >> +                            __ATOMIC_RELAXED); >> +#else >> +            success = rte_atomic32_cmpset(&r->cons.head, *old_head, >> +                    *new_head); >> +#endif > Same as above comment > >> +    } while (unlikely(success == 0)); >> +    return n; >> +} >> + >> +/** >> + * @internal Dequeue several objects from the ring >> + * >> + * @param r >> + *   A pointer to the ring structure. >> + * @param obj_table >> + *   A pointer to a table of void * pointers (objects). >> + * @param n >> + *   The number of objects to pull from the ring. >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Dequeue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Dequeue as many items as possible from ring >> + * @param is_sc >> + *   Indicates whether to use single consumer or multi-consumer head update >> + * @param available >> + *   returns the number of remaining ring entries after the dequeue has >> finished >> + * @return >> + *   - Actual number of objects dequeued. >> + *     If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_do_dequeue(struct rte_ring *r, void **obj_table, >> +         unsigned int n, enum rte_ring_queue_behavior behavior, >> +         int is_sc, unsigned int *available) >> +{ > Duplicate function, No need to replicate on both versions. > > >> +    uint32_t cons_head, cons_next; >> +    uint32_t entries; >> + >> +    n = __rte_ring_move_cons_head(r, is_sc, n, behavior, >> +            &cons_head, &cons_next, &entries); >> +    if (n == 0) >> +        goto end; >> + >> +    DEQUEUE_PTRS(r, &r[1], cons_head, obj_table, n, void *); >> + >> +    update_tail(&r->cons, cons_head, cons_next, is_sc, 0); >> + >> +end: >> +    if (available != NULL) >> +        *available = entries - n; >> +    return n; >> +} >> + >> +#endif /* _RTE_RING_C11_MEM_H_ */ >> + >> diff --git a/lib/librte_ring/rte_ring_generic.h >> b/lib/librte_ring/rte_ring_generic.h >> new file mode 100644 >> index 0000000..0ce6d57 >> --- /dev/null >> +++ b/lib/librte_ring/rte_ring_generic.h >> @@ -0,0 +1,268 @@ >> +/*- >> + *   BSD LICENSE >> + * >> + *   Copyright(c) 2017 hxt-semitech. All rights reserved. >> + * >> + *   Redistribution and use in source and binary forms, with or without >> + *   modification, are permitted provided that the following conditions >> + *   are met: >> + * >> + *     * Redistributions of source code must retain the above copyright >> + *       notice, this list of conditions and the following disclaimer. >> + *     * Redistributions in binary form must reproduce the above copyright >> + *       notice, this list of conditions and the following disclaimer in >> + *       the documentation and/or other materials provided with the >> + *       distribution. >> + *     * Neither the name of hxt-semitech nor the names of its >> + *       contributors may be used to endorse or promote products derived >> + *       from this software without specific prior written permission. >> + * >> + *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS >> + *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT >> + *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR >> + *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT >> + *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, >> + *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT >> + *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, >> + *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY >> + *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT >> + *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE >> + *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. >> + */ >> + >> +#ifndef _RTE_RING_GENERIC_H_ >> +#define _RTE_RING_GENERIC_H_ >> + >> +static __rte_always_inline void >> +update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t >> new_val, >> +        uint32_t single, uint32_t enqueue) >> +{ >> +    if (enqueue) >> +        rte_smp_wmb(); >> +    else >> +        rte_smp_rmb(); >> +    /* >> +     * If there are other enqueues/dequeues in progress that preceded us, >> +     * we need to wait for them to complete >> +     */ >> +    if (!single) >> +        while (unlikely(ht->tail != old_val)) >> +            rte_pause(); >> + >> +    ht->tail = new_val; >> +} >> + >> +/** >> + * @internal This function updates the producer head for enqueue >> + * >> + * @param r >> + *   A pointer to the ring structure >> + * @param is_sp >> + *   Indicates whether multi-producer path is needed or not >> + * @param n >> + *   The number of elements we will want to enqueue, i.e. how far should >> the >> + *   head be moved >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Enqueue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Enqueue as many items as possible from ring >> + * @param old_head >> + *   Returns head value as it was before the move, i.e. where enqueue >> starts >> + * @param new_head >> + *   Returns the current/new head value i.e. where enqueue finishes >> + * @param free_entries >> + *   Returns the amount of free space in the ring BEFORE head was moved >> + * @return >> + *   Actual number of objects enqueued. >> + *   If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_move_prod_head(struct rte_ring *r, int is_sp, >> +        unsigned int n, enum rte_ring_queue_behavior behavior, >> +        uint32_t *old_head, uint32_t *new_head, >> +        uint32_t *free_entries) >> +{ >> +    const uint32_t capacity = r->capacity; >> +    unsigned int max = n; >> +    int success; >> + >> +    do { >> +        /* Reset n to the initial burst count */ >> +        n = max; >> + >> +        *old_head = r->prod.head; > adding rte_smp_rmb() no harm here as it is NOOP for x86 and it is > semantically correct too. > > >> +        const uint32_t cons_tail = r->cons.tail; >> +        /* >> +         *  The subtraction is done between two unsigned 32bits value >> +         * (the result is always modulo 32 bits even if we have >> +         * *old_head > cons_tail). So 'free_entries' is always between 0 >> +         * and capacity (which is < size). >> +         */ >> +        *free_entries = (capacity + cons_tail - *old_head); >> + >> +        /* check that we have enough room in ring */ >> +        if (unlikely(n > *free_entries)) >> +            n = (behavior == RTE_RING_QUEUE_FIXED) ? >> +                    0 : *free_entries; >> + >> +        if (n == 0) >> +            return 0; >> + >> +        *new_head = *old_head + n; >> +        if (is_sp) >> +            r->prod.head = *new_head, success = 1; >> +        else >> +            success = rte_atomic32_cmpset(&r->prod.head, >> +                    *old_head, *new_head); >> +    } while (unlikely(success == 0)); >> +    return n; >> +} >> + >> +/** >> + * @internal Enqueue several objects on the ring >> + * >> +  * @param r >> + *   A pointer to the ring structure. >> + * @param obj_table >> + *   A pointer to a table of void * pointers (objects). >> + * @param n >> + *   The number of objects to add in the ring from the obj_table. >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Enqueue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Enqueue as many items as possible from ring >> + * @param is_sp >> + *   Indicates whether to use single producer or multi-producer head update >> + * @param free_space >> + *   returns the amount of space after the enqueue operation has finished >> + * @return >> + *   Actual number of objects enqueued. >> + *   If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_do_enqueue(struct rte_ring *r, void * const *obj_table, >> +         unsigned int n, enum rte_ring_queue_behavior behavior, >> +         int is_sp, unsigned int *free_space) >> +{ > Duplicate function, No need to replicate on both versions. > >> + >> +/** >> + * @internal This function updates the consumer head for dequeue >> + * >> + * @param r >> + *   A pointer to the ring structure >> + * @param is_sc >> + *   Indicates whether multi-consumer path is needed or not >> + * @param n >> + *   The number of elements we will want to enqueue, i.e. how far should >> the >> + *   head be moved >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Dequeue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Dequeue as many items as possible from ring >> + * @param old_head >> + *   Returns head value as it was before the move, i.e. where dequeue >> starts >> + * @param new_head >> + *   Returns the current/new head value i.e. where dequeue finishes >> + * @param entries >> + *   Returns the number of entries in the ring BEFORE head was moved >> + * @return >> + *   - Actual number of objects dequeued. >> + *     If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_move_cons_head(struct rte_ring *r, int is_sc, >> +        unsigned int n, enum rte_ring_queue_behavior behavior, >> +        uint32_t *old_head, uint32_t *new_head, >> +        uint32_t *entries) >> +{ >> +    unsigned int max = n; >> +    int success; >> + >> +    /* move cons.head atomically */ >> +    do { >> +        /* Restore n as it may change every loop */ >> +        n = max; >> + >> +        *old_head = r->cons.head; >> +        const uint32_t prod_tail = r->prod.tail; > Same as above comment. > >> +        /* The subtraction is done between two unsigned 32bits value >> +         * (the result is always modulo 32 bits even if we have >> +         * cons_head > prod_tail). So 'entries' is always between 0 >> +         * and size(ring)-1. */ >> +        *entries = (prod_tail - *old_head); >> + >> +        /* Set the actual entries for dequeue */ >> +        if (n > *entries) >> +            n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries; >> + >> +        if (unlikely(n == 0)) >> +            return 0; >> + >> +        *new_head = *old_head + n; >> +        if (is_sc) >> +            r->cons.head = *new_head, success = 1; >> +        else >> +            success = rte_atomic32_cmpset(&r->cons.head, *old_head, >> +                    *new_head); >> +    } while (unlikely(success == 0)); >> +    return n; >> +} >> + >> +/** >> + * @internal Dequeue several objects from the ring >> + * >> + * @param r >> + *   A pointer to the ring structure. >> + * @param obj_table >> + *   A pointer to a table of void * pointers (objects). >> + * @param n >> + *   The number of objects to pull from the ring. >> + * @param behavior >> + *   RTE_RING_QUEUE_FIXED:    Dequeue a fixed number of items from a ring >> + *   RTE_RING_QUEUE_VARIABLE: Dequeue as many items as possible from ring >> + * @param is_sc >> + *   Indicates whether to use single consumer or multi-consumer head update >> + * @param available >> + *   returns the number of remaining ring entries after the dequeue has >> finished >> + * @return >> + *   - Actual number of objects dequeued. >> + *     If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only. >> + */ >> +static __rte_always_inline unsigned int >> +__rte_ring_do_dequeue(struct rte_ring *r, void **obj_table, >> +         unsigned int n, enum rte_ring_queue_behavior behavior, >> +         int is_sc, unsigned int *available) >> +{ > Duplicate function, No need to replicate on both versions. -- Cheers, Jia