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[165.204.72.6]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d43f556a4sm15924075e9.22.2025.03.19.04.23.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Mar 2025 04:23:55 -0700 (PDT) Content-Type: multipart/alternative; boundary="------------WFALB1e7gBmVlHU7xpbTHiQd" Message-ID: <48f07793-0fd4-4cdd-8568-3bd2ff63bb6a@gmail.com> Date: Wed, 19 Mar 2025 12:23:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] drm/sched: add drm_sched_prealloc_dependency_slots To: phasta@kernel.org, tvrtko.ursulin@igalia.com, dri-devel@lists.freedesktop.org, dakr@kernel.org, amd-gfx@lists.freedesktop.org References: <20250318120313.19099-1-christian.koenig@amd.com> <20250318120313.19099-2-christian.koenig@amd.com> <769f6c5788eff9459414b8ce0b056989e29773af.camel@mailbox.org> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <769f6c5788eff9459414b8ce0b056989e29773af.camel@mailbox.org> X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" This is a multi-part message in MIME format. --------------WFALB1e7gBmVlHU7xpbTHiQd Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit >> + * >> + * Return: >> + * 0 on success, or an error on failing to expand the array. >> + */ >> +int drm_sched_job_prealloc_dependency_slots(struct drm_sched_job >> *job, >> +     unsigned int num_deps) >> +{ >> + struct dma_fence *fence; >> + u32 id = 0; >> + int ret; >> + >> + while (num_deps--) { >> + fence = dma_fence_get_stub(); >> + ret = xa_alloc(&job->dependencies, &id, fence, >> xa_limit_32b, >> +        GFP_KERNEL); > So this would fill the xarr with already signaled fences which then > later will be replaced with unsignaled fences? Yes, exactly that's the idea. > Help me out here: would it also work to add NULL instead of that stub- > fence? Good question, idk. That's an implementation detail of the xarray. Tvrtko also correctly pointed out that it is most likely a bad idea to use dma_fence_is_signaled() in the critical code path. I will try to dig through the xarray behavior up and update the patch if possible. Thanks, Christian. --------------WFALB1e7gBmVlHU7xpbTHiQd Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit 
+ *
+ * Return:
+ * 0 on success, or an error on failing to expand the array.
+ */
+int drm_sched_job_prealloc_dependency_slots(struct drm_sched_job
*job,
+					    unsigned int num_deps)
+{
+	struct dma_fence *fence;
+	u32 id = 0;
+	int ret;
+
+	while (num_deps--) {
+		fence = dma_fence_get_stub();
+		ret = xa_alloc(&job->dependencies, &id, fence,
xa_limit_32b,
+			       GFP_KERNEL);

So this would fill the xarr with already signaled fences which then
later will be replaced with unsignaled fences?

Yes, exactly that's the idea.

Help me out here: would it also work to add NULL instead of that stub-
fence?

Good question, idk. That's an implementation detail of the xarray.

Tvrtko also correctly pointed out that it is most likely a bad idea to use dma_fence_is_signaled() in the critical code path.

I will try to dig through the xarray behavior up and update the patch if possible.

Thanks,
Christian.

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