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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B22FCCCD183 for ; Sat, 11 Oct 2025 08:00:28 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 42E0410E065; Sat, 11 Oct 2025 08:00:28 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=igalia.com header.i=@igalia.com header.b="oq2jOLjX"; dkim-atps=neutral Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2666010E065; Sat, 11 Oct 2025 08:00:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=KTOvwM3g7/iOua++0l9UDibDrlKeHVMbp5NoGImvgUc=; b=oq2jOLjX0NrgWB6Pg5SVF57+14 X+e0ZeEPtHSXsEWwhhivDxWjZGik7JWm3Tb7qYt85O5Xid8tQHO4mcY5A/vAmR97NSL9icbGL3Ivx apxjhanZ0hPBx0N93MR0biI/bim8PdtI2P8+jxoVgoNZLeFga6qloF92rMyQmWN8lVJu+zj8bWOiX YZ80VxbNGCcqLgez1SeofaYUJCxXFZq9Io0n8LHelw2z5TlC0d0jhu5QpO/y9qo1llUAL9Z6yT4sw LeYJB8+zG0x7vjezQao2fh4kfSg8x7cIHv937XU/ajioCH6FhQmF8Dg8VnbaF4qrl5hrrpsnr9RUi LkkwXO0Q==; Received: from [84.66.36.92] (helo=[192.168.0.101]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1v7UWX-008ATT-9s; Sat, 11 Oct 2025 10:00:17 +0200 Message-ID: <69279852-e1ed-4caf-a92b-a352ba4b613b@igalia.com> Date: Sat, 11 Oct 2025 09:00:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/5] Improving the worst case TTM large allocation latency To: =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , =?UTF-8?Q?Christian_K=C3=B6nig?= , amd-gfx@lists.freedesktop.org, Lucas De Marchi , dri-devel@lists.freedesktop.org, Rodrigo Vivi Cc: kernel-dev@igalia.com, Alex Deucher , Danilo Krummrich , Dave Airlie , Gerd Hoffmann , Joonas Lahtinen , Lyude Paul , Maarten Lankhorst , Maxime Ripard , Sui Jingfeng , Thadeu Lima de Souza Cascardo , Thomas Zimmermann , Zack Rusin References: <20251008115314.55438-1-tvrtko.ursulin@igalia.com> <6bba6d25-91f3-49a6-81fc-7a03d891cd1d@amd.com> <22228578-a03c-4fc1-85b2-d281525a2b6f@igalia.com> <9bb3c06e-25c1-43d8-a4e8-e529c53ff77d@amd.com> <45973012f925dbbfdf0636c10f9d051c34f97e2e.camel@linux.intel.com> Content-Language: en-GB From: Tvrtko Ursulin In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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" On 10/10/2025 15:11, Thomas Hellström wrote: > On Thu, 2025-10-09 at 09:53 +0100, Tvrtko Ursulin wrote: >> >> On 08/10/2025 15:39, Thomas Hellström wrote: >>> On Wed, 2025-10-08 at 16:02 +0200, Christian König wrote: >>>> On 08.10.25 15:50, Tvrtko Ursulin wrote: >>>>> >>>>> On 08/10/2025 13:35, Christian König wrote: >>>>>> On 08.10.25 13:53, Tvrtko Ursulin wrote: >>>>>>> Disclaimer: >>>>>>> Please note that as this series includes a patch which >>>>>>> touches >>>>>>> a good number of >>>>>>> drivers I will only copy everyone in the cover letter and >>>>>>> the >>>>>>> respective patch. >>>>>>> Assumption is people are subscribed to dri-devel so can >>>>>>> look at >>>>>>> the whole series >>>>>>> there. I know someone is bound to complain for both the >>>>>>> case >>>>>>> when everyone is >>>>>>> copied on everything for getting too much email, and also >>>>>>> for >>>>>>> this other case. >>>>>>> So please be flexible. >>>>>>> >>>>>>> Description: >>>>>>> >>>>>>> All drivers which use the TTM pool allocator end up >>>>>>> requesting >>>>>>> large order >>>>>>> allocations when allocating large buffers. Those can be >>>>>>> slow >>>>>>> due memory pressure >>>>>>> and so add latency to buffer creation. But there is often >>>>>>> also >>>>>>> a size limit >>>>>>> above which contiguous blocks do not bring any performance >>>>>>> benefits. This series >>>>>>> allows drivers to say when it is okay for the TTM to try a >>>>>>> bit >>>>>>> less hard. >>>>>>> >>>>>>> We do this by allowing drivers to specify this cut off >>>>>>> point >>>>>>> when creating the >>>>>>> TTM device and pools. Allocations above this size will skip >>>>>>> direct reclaim so >>>>>>> under memory pressure worst case latency will improve. >>>>>>> Background reclaim is >>>>>>> still kicked off and both before and after the memory >>>>>>> pressure >>>>>>> all the TTM pool >>>>>>> buckets remain to be used as they are today. >>>>>>> >>>>>>> This is especially interesting if someone has configured >>>>>>> MAX_PAGE_ORDER to >>>>>>> higher than the default. And even with the default, with >>>>>>> amdgpu >>>>>>> for example, >>>>>>> the last patch in the series makes use of the new feature >>>>>>> by >>>>>>> telling TTM that >>>>>>> above 2MiB we do not expect performance benefits. Which >>>>>>> makes >>>>>>> TTM not try direct >>>>>>> reclaim for the top bucket (4MiB). >>>>>>> >>>>>>> End result is TTM drivers become a tiny bit nicer mm >>>>>>> citizens >>>>>>> and users benefit >>>>>>> from better worst case buffer creation latencies. As a side >>>>>>> benefit we get rid >>>>>>> of two instances of those often very unreadable mutliple >>>>>>> nameless booleans >>>>>>> function signatures. >>>>>>> >>>>>>> If this sounds interesting and gets merge the invidual >>>>>>> drivers >>>>>>> can follow up >>>>>>> with patches configuring their thresholds. >>>>>>> >>>>>>> v2: >>>>>>>    * Christian suggested to pass in the new data by >>>>>>> changing the >>>>>>> function signatures. >>>>>>> >>>>>>> v3: >>>>>>>    * Moved ttm pool helpers into new ttm_pool_internal.h. >>>>>>> (Christian) >>>>>> >>>>>> Patch #3 is Acked-by: Christian König >>>>>> . >>>>>> >>>>>> The rest is Reviewed-by: Christian König >>>>>> >>>>> >>>>> Thank you! >>>>> >>>>> So I think now I need acks to merge via drm-misc for all the >>>>> drivers which have their own trees. Which seems to be just xe. >>>> >>>> I think you should ping the XE guys for their opinion, but since >>>> there shouldn't be any functional change for them you can >>>> probably go >>>> ahead and merge the patches to drm-misc-next when there is no >>>> reply >>>> in time. >>> >>> I will try to do a review tonight. One thing that comes up though, >>> is >>> the change to ttm_device_init() where you add pool_flags. I had >>> another >>> patch series a number of months ago that added a struct with flags >>> there instead to select the return value given when OOM. Now that >>> we're >>> adding an argument, should we try to use a struct instead so that >>> we >>> can use it for more that pool behavior? >>> >>> >>> I'll be able to find a pointer to that series later today. >> >> Found it: >> https://lore.kernel.org/dri-devel/20241002122422.287276-1-thomas.hellstrom@linux.intel.com/ >> >> Glad to see in that thread it isn't just me permanently slowed down >> by >> "false, false" and similar. :) >> >> I considered using a struct too and I guess there wasn't too much of >> a >> sway that I went with flags. I thought not to overcomplicate with the >> on >> stack struct which is mostly not needed for something so low level, >> and >> to stick with the old school C visual patterns. >> >> Since you only needed a single boolean in your series I suppose you >> could just follow up on my series if you find it acceptable. Or I can >> go >> with yours, no problem either. > > It seems yours has the most momentum ATM. I can follow up on yours. It > would be great if we could perhaps change the naming of "pool_flags" to > something more generic. Do you have a name in mind? For ttm_device_init pool_flags made sense to signify they relate only to the poll. I need to respin anyway since I forgot to include the new header from unit tests. Regards, Tvrtko