From patchwork Fri Jan 8 10:56:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 12006349 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00170C433E0 for ; Fri, 8 Jan 2021 10:56:18 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 1F26B23976 for ; Fri, 8 Jan 2021 10:56:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F26B23976 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3857389F6B; Fri, 8 Jan 2021 10:56:17 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6C4F189F6B for ; Fri, 8 Jan 2021 10:56:16 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from build.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 23536574-1500050 for multiple; Fri, 08 Jan 2021 10:56:09 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Fri, 8 Jan 2021 10:56:08 +0000 Message-Id: <20210108105608.18424-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drm/i915/selftests: Rearrange ktime_get to reduce latency against CS 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: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" In our tests where we measure the elapsed time on both the CPU and CS using a udelay, our CS results match the udelay much more accurately than the ktime (even when using ktime_get_fast_ns). With preemption disabled, we can go one step lower than ktime and use local_clock. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2919 Signed-off-by: Chris Wilson Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c index ca080445695e..c3d965279fc3 100644 --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c @@ -112,11 +112,11 @@ static int __measure_timestamps(struct intel_context *ce, /* Run the request for a 100us, sampling timestamps before/after */ preempt_disable(); - *dt = ktime_get_raw_fast_ns(); + *dt = local_clock(); write_semaphore(&sema[2], 0); udelay(100); + *dt = local_clock() - *dt; write_semaphore(&sema[2], 1); - *dt = ktime_get_raw_fast_ns() - *dt; preempt_enable(); if (i915_request_wait(rq, 0, HZ / 2) < 0) {