From patchwork Mon Apr 17 10:38:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Fabio M. De Francesco" X-Patchwork-Id: 13213680 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 782DAC77B77 for ; Mon, 17 Apr 2023 10:39:10 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2D74210E3F8; Mon, 17 Apr 2023 10:39:06 +0000 (UTC) Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by gabe.freedesktop.org (Postfix) with ESMTPS id 820FF10E3F9; Mon, 17 Apr 2023 10:39:04 +0000 (UTC) Received: by mail-wr1-x42b.google.com with SMTP id ffacd0b85a97d-2f46348728eso827551f8f.3; Mon, 17 Apr 2023 03:39:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1681727942; x=1684319942; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=mkh5X1oOnHmMtPThd/Ogb+Ei0/Iy+LdjudYL5nRHiA8=; b=XO/vfE0ttxJFtb+z+zDWyoXcM09x8Zs78N3GfyVo9gwDIuuHa3a1Gya8goc4sNmMJV vJR78/+//6TCZvI30CK/mDXRtQDDAPsnAizkwB7SubAmmPETo39N1bcxXg1o3cKdtQmJ iCoD6j4lKCLRHYwJI1MFIYJlEvuRAjgVkoOTZ/uX15pf4L+VkS92fyBzWSrLwGYY50At OR7OTpSJgtuz6ZDgg4F9K6kpnJv0D1ptjteBC4ZP3XgKXT3gyKF4/aYye3QW/JCfu8DK jN3oOf3Qkl4Z3pTExiIhOq34ri6WOzWaj3YJ2LKW9OBRVj7+1BrJHbhm4NXNHFDfBeZ8 h7ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681727942; x=1684319942; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=mkh5X1oOnHmMtPThd/Ogb+Ei0/Iy+LdjudYL5nRHiA8=; b=UTzldRWNJPKX1IRSQubx2Td5gEocn6yGLuPiUG1B6yBNRQO7CFwGDc4uZ1mO61lLSb KN3E4YMuBQfv/KLwxpYtd1fJzvlWqAhLSMMuGyb1UQ+XevEgCS0knUyYT+hFsZoFP+MN elXyxj0gm7sRo2yp0h73nI6/um1iIuXZQYulgYVoAFKwJhVpnsu/zJWhIqNjEDuZ9GNg 0sDPU5ZoSS9QvOpSkeXYq0DRaTpOAq+n2S+60uEHOe+abiKRhI1Qfk4SUALmV0xnD+Yd y3JIZvyqQge6p8yPkXLV3XwUEuCGSGmiBqMp1/tiDhI4bRlDa3yj9pxSXpw0GHl9MB2L tSxw== X-Gm-Message-State: AAQBX9c++PWXppNq5unuRiOQLT0MxdiWuzJyDvPHYKN1FM0Z+8ai8bGs RM0ljD5ZLsXWFqGoovHBpR0= X-Google-Smtp-Source: AKy350ZWcTYKgg1QBjpNgdR9wjl3y2FJYThqP4aJuL8PsgT/C8+4jSADpdmdsMu3nAzGfM6xeTh5vg== X-Received: by 2002:a5d:6606:0:b0:2f8:dd25:f96e with SMTP id n6-20020a5d6606000000b002f8dd25f96emr4345092wru.6.1681727942023; Mon, 17 Apr 2023 03:39:02 -0700 (PDT) Received: from localhost.localdomain (host-87-19-108-254.retail.telecomitalia.it. [87.19.108.254]) by smtp.gmail.com with ESMTPSA id y12-20020a5d470c000000b002c70ce264bfsm10238018wrq.76.2023.04.17.03.39.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 03:39:01 -0700 (PDT) From: "Fabio M. De Francesco" To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matt Roper , John Harrison , Daniele Ceraolo Spurio , Chris Wilson , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Mon, 17 Apr 2023 12:38:52 +0200 Message-Id: <20230417103854.23333-2-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230417103854.23333-1-fmdefrancesco@gmail.com> References: <20230417103854.23333-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH v2 1/3] drm/i915: Replace kmap() with kmap_local_page() 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: , Cc: Ira Weiny , "Fabio M. De Francesco" Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" kmap() has been deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap’s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. Obviously, thread locality implies that the kernel voirtual addresses are valid only in the context of the callers. kmap_local_page() use in i915_gem.c doesn't break the above-mentioned constraint, so it should be preferred to kmap(). Therefore, replace kmap() with kmap_local_page() in i915_gem.c Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- drivers/gpu/drm/i915/i915_gem.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) -- 2.40.0 diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 35950fa91406..c35248555e42 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -212,14 +212,14 @@ shmem_pread(struct page *page, int offset, int len, char __user *user_data, char *vaddr; int ret; - vaddr = kmap(page); + vaddr = kmap_local_page(page); if (needs_clflush) drm_clflush_virt_range(vaddr + offset, len); ret = __copy_to_user(user_data, vaddr + offset, len); - kunmap(page); + kunmap_local(vaddr); return ret ? -EFAULT : 0; } @@ -643,7 +643,7 @@ shmem_pwrite(struct page *page, int offset, int len, char __user *user_data, char *vaddr; int ret; - vaddr = kmap(page); + vaddr = kmap_local_page(page); if (needs_clflush_before) drm_clflush_virt_range(vaddr + offset, len); @@ -652,7 +652,7 @@ shmem_pwrite(struct page *page, int offset, int len, char __user *user_data, if (!ret && needs_clflush_after) drm_clflush_virt_range(vaddr + offset, len); - kunmap(page); + kunmap_local(vaddr); return ret ? -EFAULT : 0; }