From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 755701CFB6 for ; Thu, 25 Jan 2024 09:29:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=140.211.166.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706174946; cv=none; b=CilrFWKVSxsRjgozVrlzQPoqXYXTjwafyCJqRYv7ekHnPvHOgPec3mn4IYujFx5Ms7vmNwXIWu5qcZo4E8RqICzWUMHY1L5TxPcIakKQFnJBqoJN9TOvOH+nYynqeZYsHQDWj6Pa5YNMSmXWG/Aph68l8umgyW69at5zpyXutU8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706174946; c=relaxed/simple; bh=MuHOFFDvhunWa09yCKieBQeofTJm5hUil4z2V5RP7/c=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=iukdC+ECIxia2lI3KLJvQsz+uYzCb2ulEA2eMeYVGS7cQCAkGAu5vK/Ck50gnkKpV5teHtJeHhNry7ffA3k+MNar/iZCUG00Jpa1hzHrUAVr7q0lHJMmcMKub5Wow7rmDzf8Gz2a8VyvGJTpo4Ix7TKb77ael/K8EFpUsgYq9FA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=NrDb1FaB; arc=none smtp.client-ip=140.211.166.133 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="NrDb1FaB" Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id D935E43545 for ; Thu, 25 Jan 2024 09:29:04 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp2.osuosl.org D935E43545 Authentication-Results: smtp2.osuosl.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.a=rsa-sha256 header.s=mail header.b=NrDb1FaB X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -2.1 X-Spam-Level: Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id QvvYIofHeFs6 for ; Thu, 25 Jan 2024 09:29:04 +0000 (UTC) Received: from madrid.collaboradmins.com (madrid.collaboradmins.com [46.235.227.194]) by smtp2.osuosl.org (Postfix) with ESMTPS id C379A42F4E for ; Thu, 25 Jan 2024 09:29:03 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp2.osuosl.org C379A42F4E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1706174941; bh=MuHOFFDvhunWa09yCKieBQeofTJm5hUil4z2V5RP7/c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NrDb1FaBaq13ye++Lhg9rKsUJUXv0CRes27oB17iSRjJI+f260kZqghxxIZiHPzKF yG6w09yncfIcrwFhoeCGYZ/UGRPOvZj+BlKCoxh0Kbrzd/cMl51zO7QWS4loE7xDkx R8JmJ/OZjwElQbafLdkoQovcnyaDjPRBNW5oDS+E7/hS0AKI10hMKA1rvqLulArOiC /gg8mIL23r6i4JVwuVbbfG5bPGMGvlO5PRxPX3vXd/g/7vPtHw838An9VQnD8DfxH8 vXnkf3u1PESFA9piBvV8wC2PNTy0r3VVjSEBCViVMZWseP6/oklRc8Ydq8iLOdBE1v tbEsIRBp4/X9w== 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 E09AB378000B; Thu, 25 Jan 2024 09:29:00 +0000 (UTC) Date: Thu, 25 Jan 2024 10:28:59 +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 24/30] drm/shmem-helper: Optimize unlocked get_pages_sgt() Message-ID: <20240125102859.6d8a864f@collabora.com> In-Reply-To: <20240105184624.508603-25-dmitry.osipenko@collabora.com> References: <20240105184624.508603-1-dmitry.osipenko@collabora.com> <20240105184624.508603-25-dmitry.osipenko@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: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 5 Jan 2024 21:46:18 +0300 Dmitry Osipenko wrote: > SGT isn't refcounted. Once SGT pointer has been obtained, it remains the > same for both locked and unlocked get_pages_sgt(). Return cached SGT > directly without taking a potentially expensive lock. > > Signed-off-by: Dmitry Osipenko Reviewed-by: Boris Brezillon but I'm wondering if we should have made this change directly in 'drm/shmem-helper: Change sgt allocation policy'. > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 8fd7851c088b..e6e6e693ab95 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -962,6 +962,18 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem) > drm_WARN_ON(obj->dev, drm_gem_shmem_is_purgeable(shmem))) > return ERR_PTR(-EBUSY); > > + /* > + * Drivers that use shrinker should take into account that shrinker > + * may relocate BO, thus invalidating the returned SGT pointer. > + * Such drivers should pin GEM while they use SGT. > + * > + * Drivers that don't use shrinker should take into account that > + * SGT is released together with the GEM pages. Pages should be kept > + * alive while SGT is used. > + */ > + if (shmem->sgt) > + return shmem->sgt; > + > ret = dma_resv_lock_interruptible(shmem->base.resv, NULL); > if (ret) > return ERR_PTR(ret);