From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DB4D0204C1A; Wed, 5 Feb 2025 21:19:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738790349; cv=none; b=r+TzoLP0k+0Y7NrsDKiTu6tVqRTpo+G5o04f+hEU5Rb2FtdYfvcL9HPTEAyBPajvSvQtV83GcDRMQmxsHb1F3SuoVo2OtwWXCXMnXJbirkSXqknbBGQqkfHbB8Ie2tUKVd4v/ndwzaCULWupF+qwvieZRTca4DeCwPYCT6xZ7Rk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738790349; c=relaxed/simple; bh=TXjJa2DAg7tFzurNG6XXhDuq/rBlGzBXwXz5iXljRkI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hau7BYIWIDqAg8rO90iJXx82Yw/BF4FQ5biTn5utOfSwgM/HPsouHacW33bKuZ4KHmtDD8DpKSyF38aIvAAzjxUYWW5yGDwwimem5jabTq31ooaB1ElKTnfQqhub1F2Lbllz/5rUw2PzRl15Zl/705m5Q+hKgmc+eJhaWSPk8Zo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7DA0C4CED1; Wed, 5 Feb 2025 21:19:05 +0000 (UTC) Date: Wed, 5 Feb 2025 16:19:45 -0500 From: Steven Rostedt To: Prakash Sangappa Cc: Joel Fernandes , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "linux-trace-kernel@vger.kernel.org" , Thomas Gleixner , Ankur Arora , Linus Torvalds , "linux-mm@kvack.org" , "x86@kernel.org" , Andrew Morton , "luto@kernel.org" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "hpa@zytor.com" , "juri.lelli@redhat.com" , "vincent.guittot@linaro.org" , "willy@infradead.org" , "mgorman@suse.de" , "jon.grimm@amd.com" , "bharata@amd.com" , "raghavendra.kt@amd.com" , Boris Ostrovsky , Konrad Wilk , "jgross@suse.com" , "Andrew.Cooper3@citrix.com" , Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Mathieu Desnoyers , Clark Williams , "bigeasy@linutronix.de" , "daniel.wagner@suse.com" , Joseph Salisbury , "broonie@gmail.com" Subject: Re: [RFC][PATCH 1/2] sched: Extended scheduler time slice Message-ID: <20250205161945.44daf018@gandalf.local.home> In-Reply-To: <1A67C4F1-F07E-477C-9781-071546AE3A8B@oracle.com> References: <9DA1FAE6-A008-4785-BDF9-541457E29807@joelfernandes.org> <20250204220418.35949317@gandalf.local.home> <20250205081635.397eacb0@gandalf.local.home> <1A67C4F1-F07E-477C-9781-071546AE3A8B@oracle.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-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 Wed, 5 Feb 2025 21:08:47 +0000 Prakash Sangappa wrote: > The new syscall/API proposed was to provide per thread shared mapped > area(shared structure) that are allocated from memory pages that are pinned. > So the kernel could access it without the need for a copyin/copyout. > > The idea is that it would be helpful in places where we cannot take a page > fault in the kernel codepath. What places do we need to decided this in a critical path? If we follow my proposal, where we set NEED_RESCHED_LAZY on sched_tick when it interrupts user space, then it should all work out. I agree with Peter about not caring about system calls. If you can do a system call in a critical path, then just use futexes. The only reason I support system calls is for debugging. That's because I write into the trace_marker from user space to see if things are working, and that requires a system call. But once things are working, I'll make it not work for system calls too. -- Steve