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 05123C433F5 for ; Wed, 22 Sep 2021 12:20:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5D3A61156 for ; Wed, 22 Sep 2021 12:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235227AbhIVMWC (ORCPT ); Wed, 22 Sep 2021 08:22:02 -0400 Received: from mga14.intel.com ([192.55.52.115]:15220 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233626AbhIVMWC (ORCPT ); Wed, 22 Sep 2021 08:22:02 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="223225227" X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="223225227" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 05:20:32 -0700 X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="703740646" 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 05:20:31 -0700 Subject: Re: [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl 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> <4c357136-3279-ff57-1c4f-62276534c887@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <6f8140bd-9cff-e0d8-e014-b3fb8d2d8ab0@linux.intel.com> Date: Wed, 22 Sep 2021 13:20:29 +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: 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 13:15, Christian König wrote: > Am 22.09.21 um 13:46 schrieb Tvrtko Ursulin: >> >> 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. > > Well previously we would have allocated memory, which as far as I know > has more overhead than a few extra atomic operations. It doesn't, it only uses dma_resv_excl_fence and dma_resv_shared_list. Regards, Tvrtko > On the other hand I could as well stick with dma_resv_get_fences() here. > > Regards, > Christian. > >> >> 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=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 9E741C433FE for ; Wed, 22 Sep 2021 12:20:35 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4181261156 for ; Wed, 22 Sep 2021 12:20:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 4181261156 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 392AF6EB91; Wed, 22 Sep 2021 12:20:34 +0000 (UTC) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id 726DA6EB97; Wed, 22 Sep 2021 12:20:33 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="223622212" X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="223622212" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 05:20:32 -0700 X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="703740646" 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 05:20:31 -0700 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> <4c357136-3279-ff57-1c4f-62276534c887@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <6f8140bd-9cff-e0d8-e014-b3fb8d2d8ab0@linux.intel.com> Date: Wed, 22 Sep 2021 13:20:29 +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: 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 13:15, Christian König wrote: > Am 22.09.21 um 13:46 schrieb Tvrtko Ursulin: >> >> 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. > > Well previously we would have allocated memory, which as far as I know > has more overhead than a few extra atomic operations. It doesn't, it only uses dma_resv_excl_fence and dma_resv_shared_list. Regards, Tvrtko > On the other hand I could as well stick with dma_resv_get_fences() here. > > Regards, > Christian. > >> >> 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: >>>> >