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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 C0E5AC43460 for ; Wed, 28 Apr 2021 10:27:46 +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 CD8C9613FF for ; Wed, 28 Apr 2021 10:27:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CD8C9613FF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0448A6E0AA; Wed, 28 Apr 2021 10:27:44 +0000 (UTC) Received: from mail-wm1-x32d.google.com (mail-wm1-x32d.google.com [IPv6:2a00:1450:4864:20::32d]) by gabe.freedesktop.org (Postfix) with ESMTPS id 70E8F6E08A for ; Wed, 28 Apr 2021 10:27:41 +0000 (UTC) Received: by mail-wm1-x32d.google.com with SMTP id n4-20020a05600c4f84b029013151278decso8489253wmq.4 for ; Wed, 28 Apr 2021 03:27:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=UqWIQEo2ISG2YbntxG4VDqsNdsTJRz+EP3ztYwpOKqg=; b=QoxoGHfsGu/iAKgHdK4HVK/ix0osYct+ejhxBa5m7s6hnv1FfGhfXmuoAIth7Qg7tu 4vp2DW2RJgdyrBfqAUvJNd24drbtZ64w636mS8lEr5Opvl3IUskLmjpchVXjkSk95n8N nllCx+fIGSykl6CzY2rwfNZIo5+TrkChQtUZk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=UqWIQEo2ISG2YbntxG4VDqsNdsTJRz+EP3ztYwpOKqg=; b=GqQ/h2TzY1RACT+djyVud01w3n226buAZ4Hx+3rqfl6srRc/B+lxhoA8HCP8n5ecmL qpBR1rkoGN5X8PmC3l7TO17Qc6sG004k5Pb9u2MvmQF6b55z0X0Bik4+Tno3UOc6XWPa vhyhY7ZxIVwIoKGMSquBiNaAUJcKLaSjjojllDno9sZrexWyK8Pef5BOMl3mhmikNDM0 AvclQvr8dTHbCMAGl9Me+OEsJ4ew4u8lb3WDWxb4oQ2QRFthHUO6vE7DGIQVL1qer4wx 8p382Uv/+uMJXQ0DrtC4/3gRhSofUk8zeHC0SnZrYtBHAtIRan3TgaRHUkSl0v4Urmaq CMyA== X-Gm-Message-State: AOAM530VMkPTAUqq1BdvVddbm5fzTYjeliM+3nnG4bWpEST2IrRK9UvD IZauIgFIDaoVJ1vBFIluEfoRKg== X-Google-Smtp-Source: ABdhPJz8MloVYLB2dO4kddPzJxe1xCBp+4SnZrUsj6oamcfsBW/kv7dvZstxBe1u+cbPMmUEbH1sNA== X-Received: by 2002:a1c:55ca:: with SMTP id j193mr3651617wmb.58.1619605660197; Wed, 28 Apr 2021 03:27:40 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id s16sm5661395wmh.11.2021.04.28.03.27.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 03:27:39 -0700 (PDT) Date: Wed, 28 Apr 2021 12:27:37 +0200 From: Daniel Vetter To: Jason Ekstrand Subject: Re: [PATCH 11/21] drm/i915: Stop manually RCU banging in reset_stats_ioctl Message-ID: References: <20210423223131.879208-1-jason@jlekstrand.net> <20210423223131.879208-12-jason@jlekstrand.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210423223131.879208-12-jason@jlekstrand.net> X-Operating-System: Linux phenom 5.10.32scarlett+ X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, Apr 23, 2021 at 05:31:21PM -0500, Jason Ekstrand wrote: > As far as I can tell, the only real reason for this is to avoid taking a > reference to the i915_gem_context. The cost of those two atomics > probably pales in comparison to the cost of the ioctl itself so we're > really not buying ourselves anything here. We're about to make context > lookup a tiny bit more complicated, so let's get rid of the one hand- > rolled case. I think the historical reason here is that i965_brw checks this before every execbuf call, at least for arb_robustness contexts with the right flag. But we've fixed that hotpath problem by adding non-recoverable contexts. The kernel will tell you now automatically, for proper userspace at least (I checked iris and anv, assuming I got it correct), and reset_stats ioctl isn't a hot path worth micro-optimizing anymore. With that bit of more context added to the commit message: Reviewed-by: Daniel Vetter > > Signed-off-by: Jason Ekstrand > --- > drivers/gpu/drm/i915/gem/i915_gem_context.c | 13 ++++--------- > drivers/gpu/drm/i915/i915_drv.h | 8 +------- > 2 files changed, 5 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c > index ecb3bf5369857..941fbf78267b4 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c > @@ -2090,16 +2090,13 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, > struct drm_i915_private *i915 = to_i915(dev); > struct drm_i915_reset_stats *args = data; > struct i915_gem_context *ctx; > - int ret; > > if (args->flags || args->pad) > return -EINVAL; > > - ret = -ENOENT; > - rcu_read_lock(); > - ctx = __i915_gem_context_lookup_rcu(file->driver_priv, args->ctx_id); > + ctx = i915_gem_context_lookup(file->driver_priv, args->ctx_id); > if (!ctx) > - goto out; > + return -ENOENT; > > /* > * We opt for unserialised reads here. This may result in tearing > @@ -2116,10 +2113,8 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, > args->batch_active = atomic_read(&ctx->guilty_count); > args->batch_pending = atomic_read(&ctx->active_count); > > - ret = 0; > -out: > - rcu_read_unlock(); > - return ret; > + i915_gem_context_put(ctx); > + return 0; > } > > /* GEM context-engines iterator: for_each_gem_engine() */ > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 0b44333eb7033..8571c5c1509a7 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -1840,19 +1840,13 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev, > > struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags); > > -static inline struct i915_gem_context * > -__i915_gem_context_lookup_rcu(struct drm_i915_file_private *file_priv, u32 id) > -{ > - return xa_load(&file_priv->context_xa, id); > -} > - > static inline struct i915_gem_context * > i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id) > { > struct i915_gem_context *ctx; > > rcu_read_lock(); > - ctx = __i915_gem_context_lookup_rcu(file_priv, id); > + ctx = xa_load(&file_priv->context_xa, id); > if (ctx && !kref_get_unless_zero(&ctx->ref)) > ctx = NULL; > rcu_read_unlock(); > -- > 2.31.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel