From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from madrid.collaboradmins.com (madrid.collaboradmins.com [46.235.227.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4701754F82 for ; Mon, 29 Jan 2024 08:55:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.235.227.194 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706518516; cv=none; b=CTCMrYoFq55Qcn1WyY4MMKADLHn+hsPU1mMfAImIUiwq67A0OOnQcjZOz1Uk0E8+gKhuAUPLn8OKEFOau3xw8FZWxogbBlfFRU2QT0xCH81xMJ6TTxGKNwEW1+W29yv8S+GB/XAE4kMngTYu2x1lW8KFUrV7PJYC3NjwJHystfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706518516; c=relaxed/simple; bh=xLQlDgS8uevy1Wf+yRGr1xMGsI9r43Mqvjl7x16vqyo=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=D2aWR/ITMKPE7iQwIEwPf4UfDfFY+8oYl+JA20jawvITScEzMvpPzngVIC+ax97Cxt7X0jMDpTaJdFfk0ah3Pn3j6dKBf1Z+JoXcjP9oCiHK78bQHQ5wm46WUAnlNyVPrIQGz15tLzUaiJxwKTT7VcUB5xat73/njaSsS+ePgZA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=Rg2U//TU; arc=none smtp.client-ip=46.235.227.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="Rg2U//TU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1706518513; bh=xLQlDgS8uevy1Wf+yRGr1xMGsI9r43Mqvjl7x16vqyo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Rg2U//TUJ3KYyQnPpd0pX3z282Bd+kOxagTa1g28OSE2xZmI3hsWAO0++Hw6tijwz Kscj43fTyD2ichBFYZ7+n/xM+Ll9y8DPK448ldrhJff8dTwHNpBsQmPioq9kE+jgA+ finmVnHCc/TnyoO/gYWhgHUP4PdiwNlj+olAehCax+lhdvCpTp9PdkapQhiP5KzrJ/ IMMdFF/nJ9xZJ+XVqk8VAw+cbAxoq7+SGHSUx6HpcMmYk7JK04RzGBNIRtzSiyWTtm 2eXBpgt4ciX/JkvXx06mq+j/E0NOyPsCg3zGOc6IURqd5IprR9GABjGlh3VHiajFoa ty3alJCXPlg5A== Received: from localhost (cola.collaboradmins.com [195.201.22.229]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madrid.collaboradmins.com (Postfix) with ESMTPSA id 42CE337814A4; Mon, 29 Jan 2024 08:55:12 +0000 (UTC) Date: Mon, 29 Jan 2024 09:55:11 +0100 From: Boris Brezillon To: Dmitry Osipenko Cc: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Christian =?UTF-8?B?S8O2bmln?= , Qiang Yu , Steven Price , Emma Anholt , Melissa Wen , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v19 22/30] drm/shmem-helper: Add common memory shrinker Message-ID: <20240129095511.31f8a2af@collabora.com> In-Reply-To: References: <20240105184624.508603-1-dmitry.osipenko@collabora.com> <20240105184624.508603-23-dmitry.osipenko@collabora.com> <20240125111946.797a1e1e@collabora.com> <20240126105537.67b1613e@collabora.com> <20240126191230.0ee6f99f@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.2.0 (GTK 3.24.38; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 29 Jan 2024 09:16:04 +0300 Dmitry Osipenko wrote: > On 1/26/24 21:12, Boris Brezillon wrote: > > On Fri, 26 Jan 2024 19:27:49 +0300 > > Dmitry Osipenko wrote: > > > >> On 1/26/24 12:55, Boris Brezillon wrote: > >>> On Fri, 26 Jan 2024 00:56:47 +0300 > >>> Dmitry Osipenko wrote: > >>> > >>>> On 1/25/24 13:19, Boris Brezillon wrote: > >>>>> On Fri, 5 Jan 2024 21:46:16 +0300 > >>>>> Dmitry Osipenko wrote: > >>>>> > >>>>>> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem) > >>>>>> +{ > >>>>>> + return (shmem->madv >= 0) && shmem->base.funcs->evict && > >>>>>> + refcount_read(&shmem->pages_use_count) && > >>>>>> + !refcount_read(&shmem->pages_pin_count) && > >>>>>> + !shmem->base.dma_buf && !shmem->base.import_attach && > >>>>>> + !shmem->evicted; > >>>>> > >>>>> Are we missing > >>>>> > >>>>> && dma_resv_test_signaled(shmem->base.resv, > >>>>> DMA_RESV_USAGE_BOOKKEEP) > >>>>> > >>>>> to make sure the GPU is done using the BO? > >>>>> The same applies to drm_gem_shmem_is_purgeable() BTW. > >>>>> > >>>>> If you don't want to do this test here, we need a way to let drivers > >>>>> provide a custom is_{evictable,purgeable}() test. > >>>>> > >>>>> I guess we should also expose drm_gem_shmem_shrinker_update_lru_locked() > >>>>> to let drivers move the GEMs that were used most recently (those > >>>>> referenced by a GPU job) at the end of the evictable LRU. > >>>> > >>>> We have the signaled-check in the common drm_gem_evict() helper: > >>>> > >>>> https://elixir.bootlin.com/linux/v6.8-rc1/source/drivers/gpu/drm/drm_gem.c#L1496 > >>> > >>> Ah, indeed. I'll need DMA_RESV_USAGE_BOOKKEEP instead of > >>> DMA_RESV_USAGE_READ in panthor, but I can add it in the driver specific > >>> ->evict() hook (though that means calling dma_resv_test_signaled() > >>> twice, which is not great, oh well). > >> > >> Maybe we should change drm_gem_evict() to use BOOKKEEP. The > >> test_signaled(BOOKKEEP) should be a "stronger" check than > >> test_signaled(READ)? > > > > It is, just wondering if some users have a good reason to want > > READ here. > > > >> > >>> The problem about the evictable LRU remains though: we need a way to let > >>> drivers put their BOs at the end of the list when the BO has been used > >>> by the GPU, don't we? > >> > >> If BO is use, then it won't be evicted, while idling BOs will be > >> evicted. Hence, the used BOs will be naturally moved down the LRU list > >> each time shrinker is invoked. > >> > > > > That only do the trick if the BOs being used most often are busy when > > the shrinker kicks in though. Let's take this scenario: > > > > > > BO 1 BO 2 shinker > > > > busy > > idle (first-pos-in-evictable-LRU) > > > > busy > > idle (second-pos-in-evictable-LRU) > > > > busy > > idle > > > > busy > > idle > > > > busy > > idle > > > > find a BO to evict > > pick BO 2 > > > > busy (swapin) > > idle > > > > If the LRU had been updated at each busy event, BO 1 should have > > been picked for eviction. But we evicted the BO that was first > > recorded idle instead of the one that was least recently > > recorded busy. > > You have to swapin(BO) every time BO goes to busy state, and swapin does drm_gem_lru_move_tail(BO). Hence, each time BO goes idle->busy, it's moved down the LRU list. Ah, that's the bit I was missing. It makes sense now. I guess that's good enough for now, we can sort out the BOOKKEEP vs READ in a follow-up series. Reviewed-by: Boris Brezillon