From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 753091DFFC for ; Mon, 20 Jan 2025 12:23:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737375814; cv=none; b=NaFFLh9gV4GCtacO3HE9AmCvWm/9MSSrfpHTIvCTdkeT2r4JOqMAYfEUg5W9d6qriiXMFY7BWYVpZiwRDej4jqYY6u6u2z1yNMsGva9NDNZfhr/RxEmuidis9AOFjKGfm5sPfEPn7U0VeDCpHF/yZkOrr88bKOr26zD/5R0BoOg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737375814; c=relaxed/simple; bh=UaTzTANVudPEZxpSfU2G4TBv9B+w00ZKRmEE6dV8LT8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kMVzPz8i0g+HAfmaY9ZFYdKF4CxIGWGuf98m+5t53fbAdwP8S4dDW4gUyChJdmxh6dJT681/3yBuvP31ERrAvGs+DW9DUohF7FzSrWqb9/mz6yo6EBeL/lxmfZlx7zHrIDUMjUiA9elnwMF6ftqTwbg9qR0xZ4Xn0rM3Lsff3SM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Bwn5Xu+0; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Bwn5Xu+0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737375811; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UaTzTANVudPEZxpSfU2G4TBv9B+w00ZKRmEE6dV8LT8=; b=Bwn5Xu+0cez+lW8jlmuwLV/tTW1RK7otoLhEOCmkymfFdsrKAuGkmERkNjbIpDs2ZuEKE8 9Nt3lp0yS9oeKtA+FKUl6qPfYAvLAmnrYj/ANKP9MJ6RQpleIdU45WbQJ9N+qM6csatSmv JZTBE7ZxI+WuFqbeViwV6DtyguPofro= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-58-CMDVTjksPZOAiifCjJ6gMg-1; Mon, 20 Jan 2025 07:23:27 -0500 X-MC-Unique: CMDVTjksPZOAiifCjJ6gMg-1 X-Mimecast-MFC-AGG-ID: CMDVTjksPZOAiifCjJ6gMg Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E0F97195605B; Mon, 20 Jan 2025 12:23:25 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.104]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id E142F3003FD9; Mon, 20 Jan 2025 12:23:22 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jan 2025 13:23:00 +0100 (CET) Date: Mon, 20 Jan 2025 13:22:56 +0100 From: Oleg Nesterov To: Mateusz Guzik Cc: kernel test robot , oe-lkp@lists.linux.dev, lkp@intel.com, Christian Brauner , WangYuli , linux-fsdevel@vger.kernel.org Subject: Re: [linux-next:master] [pipe_read] aaec5a95d5: stress-ng.poll.ops_per_sec 11.1% regression Message-ID: <20250120121928.GA7432@redhat.com> References: <202501201311.6d25a0b9-lkp@intel.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On 01/20, Mateusz Guzik wrote: > > Whatever the long term fate of the patch I think it would be prudent to > skip it in this merge window. Perhaps... I'll try to take another look tomorrow. Just one note right now. > First two notes: > 1. the change only considers performing a wake up if the current > source buf got depleted -- if there is a blocked writer and there is at > least one byte in the current buf nothing happens, which is where the > difference in results is coming from Sorry I don't understand. Unless this patch is buggy, pipe_read() must always wakeup a blocked writer if the writer can write at least one byte. The writer can't write to "current" buf = pipe->bufs[tail & mask] if pipe_full() is still true. Oleg.