From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DC4FC433F5 for ; Wed, 22 Sep 2021 11:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C81F60FA0 for ; Wed, 22 Sep 2021 11:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235787AbhIVLsV (ORCPT ); Wed, 22 Sep 2021 07:48:21 -0400 Received: from mga06.intel.com ([134.134.136.31]:46367 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230171AbhIVLsU (ORCPT ); Wed, 22 Sep 2021 07:48:20 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="284586866" X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="284586866" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 04:46:49 -0700 X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="703689779" Received: from bbrowne-mobl.ger.corp.intel.com (HELO [10.213.200.151]) ([10.213.200.151]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 04:46:47 -0700 Subject: Re: [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl From: Tvrtko Ursulin To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210922091044.2612-1-christian.koenig@amd.com> <20210922091044.2612-14-christian.koenig@amd.com> <6b22cb75-6c41-db55-83f2-3eae87b585aa@linux.intel.com> Organization: Intel Corporation UK Plc Message-ID: <4c357136-3279-ff57-1c4f-62276534c887@linux.intel.com> Date: Wed, 22 Sep 2021 12:46:46 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <6b22cb75-6c41-db55-83f2-3eae87b585aa@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 22/09/2021 11:21, Tvrtko Ursulin wrote: > > On 22/09/2021 10:10, Christian König wrote: >> This makes the function much simpler since the complex >> retry logic is now handled else where. >> >> Signed-off-by: Christian König >> --- >>   drivers/gpu/drm/i915/gem/i915_gem_busy.c | 35 ++++++++++-------------- >>   1 file changed, 14 insertions(+), 21 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> index 6234e17259c1..313afb4a11c7 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> @@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, >>   { >>       struct drm_i915_gem_busy *args = data; >>       struct drm_i915_gem_object *obj; >> -    struct dma_resv_list *list; >> -    unsigned int seq; >> +    struct dma_resv_iter cursor; >> +    struct dma_fence *fence; >>       int err; >>       err = -ENOENT; >> @@ -109,27 +109,20 @@ i915_gem_busy_ioctl(struct drm_device *dev, void >> *data, >>        * to report the overall busyness. This is what the wait-ioctl >> does. >>        * >>        */ >> -retry: >> -    seq = raw_read_seqcount(&obj->base.resv->seq); >> - >> -    /* Translate the exclusive fence to the READ *and* WRITE engine */ >> -    args->busy = busy_check_writer(dma_resv_excl_fence(obj->base.resv)); >> - >> -    /* Translate shared fences to READ set of engines */ >> -    list = dma_resv_shared_list(obj->base.resv); >> -    if (list) { >> -        unsigned int shared_count = list->shared_count, i; >> - >> -        for (i = 0; i < shared_count; ++i) { >> -            struct dma_fence *fence = >> -                rcu_dereference(list->shared[i]); >> - >> +    args->busy = false; > > You can drop this line, especially since it is not a boolean. With that: > > Reviewed-by: Tvrtko Ursulin Having said this, one thing to add in the commit message is some commentary that although simpler in code, the new implementation has a lot more atomic instructions due all the extra fence get/put. Saying this because I remembered busy ioctl is quite an over-popular one. Thinking about traces from some real userspaces I looked at in the past. So I think ack from maintainers will be required here. Because I just don't know if any performance impact will be visible or not. So view my r-b as "code looks fine" but I am on the fence if it should actually be merged. Probably leaning towards no actually - given how the code is localised here and I dislike burdening old platforms with more CPU time it could be cheaply left as is. Regards, Tvrtko > > Regards, > > Tvrtko > >> +    dma_resv_iter_begin(&cursor, obj->base.resv, true); >> +    dma_resv_for_each_fence_unlocked(&cursor, fence) { >> +        if (dma_resv_iter_is_restarted(&cursor)) >> +            args->busy = 0; >> + >> +        if (dma_resv_iter_is_exclusive(&cursor)) >> +            /* Translate the exclusive fence to the READ *and* WRITE >> engine */ >> +            args->busy |= busy_check_writer(fence); >> +        else >> +            /* Translate shared fences to READ set of engines */ >>               args->busy |= busy_check_reader(fence); >> -        } >>       } >> - >> -    if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq)) >> -        goto retry; >> +    dma_resv_iter_end(&cursor); >>       err = 0; >>   out: >> From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42FA4C433EF for ; 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22 Sep 2021 04:46:49 -0700 X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="703689779" Received: from bbrowne-mobl.ger.corp.intel.com (HELO [10.213.200.151]) ([10.213.200.151]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 04:46:47 -0700 From: Tvrtko Ursulin To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210922091044.2612-1-christian.koenig@amd.com> <20210922091044.2612-14-christian.koenig@amd.com> <6b22cb75-6c41-db55-83f2-3eae87b585aa@linux.intel.com> Organization: Intel Corporation UK Plc Message-ID: <4c357136-3279-ff57-1c4f-62276534c887@linux.intel.com> Date: Wed, 22 Sep 2021 12:46:46 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <6b22cb75-6c41-db55-83f2-3eae87b585aa@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [Intel-gfx] [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 22/09/2021 11:21, Tvrtko Ursulin wrote: > > On 22/09/2021 10:10, Christian König wrote: >> This makes the function much simpler since the complex >> retry logic is now handled else where. >> >> Signed-off-by: Christian König >> --- >>   drivers/gpu/drm/i915/gem/i915_gem_busy.c | 35 ++++++++++-------------- >>   1 file changed, 14 insertions(+), 21 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> index 6234e17259c1..313afb4a11c7 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >> @@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, >>   { >>       struct drm_i915_gem_busy *args = data; >>       struct drm_i915_gem_object *obj; >> -    struct dma_resv_list *list; >> -    unsigned int seq; >> +    struct dma_resv_iter cursor; >> +    struct dma_fence *fence; >>       int err; >>       err = -ENOENT; >> @@ -109,27 +109,20 @@ i915_gem_busy_ioctl(struct drm_device *dev, void >> *data, >>        * to report the overall busyness. This is what the wait-ioctl >> does. >>        * >>        */ >> -retry: >> -    seq = raw_read_seqcount(&obj->base.resv->seq); >> - >> -    /* Translate the exclusive fence to the READ *and* WRITE engine */ >> -    args->busy = busy_check_writer(dma_resv_excl_fence(obj->base.resv)); >> - >> -    /* Translate shared fences to READ set of engines */ >> -    list = dma_resv_shared_list(obj->base.resv); >> -    if (list) { >> -        unsigned int shared_count = list->shared_count, i; >> - >> -        for (i = 0; i < shared_count; ++i) { >> -            struct dma_fence *fence = >> -                rcu_dereference(list->shared[i]); >> - >> +    args->busy = false; > > You can drop this line, especially since it is not a boolean. With that: > > Reviewed-by: Tvrtko Ursulin Having said this, one thing to add in the commit message is some commentary that although simpler in code, the new implementation has a lot more atomic instructions due all the extra fence get/put. Saying this because I remembered busy ioctl is quite an over-popular one. Thinking about traces from some real userspaces I looked at in the past. So I think ack from maintainers will be required here. Because I just don't know if any performance impact will be visible or not. So view my r-b as "code looks fine" but I am on the fence if it should actually be merged. Probably leaning towards no actually - given how the code is localised here and I dislike burdening old platforms with more CPU time it could be cheaply left as is. Regards, Tvrtko > > Regards, > > Tvrtko > >> +    dma_resv_iter_begin(&cursor, obj->base.resv, true); >> +    dma_resv_for_each_fence_unlocked(&cursor, fence) { >> +        if (dma_resv_iter_is_restarted(&cursor)) >> +            args->busy = 0; >> + >> +        if (dma_resv_iter_is_exclusive(&cursor)) >> +            /* Translate the exclusive fence to the READ *and* WRITE >> engine */ >> +            args->busy |= busy_check_writer(fence); >> +        else >> +            /* Translate shared fences to READ set of engines */ >>               args->busy |= busy_check_reader(fence); >> -        } >>       } >> - >> -    if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq)) >> -        goto retry; >> +    dma_resv_iter_end(&cursor); >>       err = 0; >>   out: >>