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 848261DFE14 for ; Mon, 20 Jan 2025 12:42:48 +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=1737376970; cv=none; b=UMi09iZtSLh4ATBnmsOFtYGIluQwdff3YhQ6Tbxz4MeqLbjnFBX/FlFdREr1vDgGRmB7CtEVlfN57xyfIFcqeDXwKxZKyMSqnt3sUzOplx/7/3104Jm6WJ8BXygM/OHroZswF7l/t+W4gbzJArIqriX9C9zpbmST8i5LP7jG90k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737376970; c=relaxed/simple; bh=ljOvUhnQMd/bR+2NO4+rfciOdIOy6YM2mR6nKravZng=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JPhYBejDGB9kezrvleg0dUZuHdzQCZW3WRbeRDRUiYfJBLkGAE4X7lxI3dQlHgsGG2rea4WQjyJhf7qCQKZuJ6Y0eIzSPaDflJXOck/fLs8Rk+vGwMMPy0HO0BxBsBbVcjkTXbDgkRJb7jKbWNgnet7M1qstHxqe9+N/WaXWoek= 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=Dv6iEKv3; 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="Dv6iEKv3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737376967; 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=ljOvUhnQMd/bR+2NO4+rfciOdIOy6YM2mR6nKravZng=; b=Dv6iEKv3Nrco62GIP0rTxZJ3MKWxVtQ6QzGc+2BfNw/w0PMB4m9BfaxgpUJ8vIN/5G2ggv I9nQH9kejzT2Tp4BzBJ/6q58T8tkrgpHqUoKhZbci2Kepw+FPMBV4T6bN8WtjNZfcueUSc fPmNC6Lj2jUP5LnHjj9GHnK6Ab3ExLE= Received: from mx-prod-mc-02.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-250-DuTuzjEFNteS6GqyxJJMrg-1; Mon, 20 Jan 2025 07:42:42 -0500 X-MC-Unique: DuTuzjEFNteS6GqyxJJMrg-1 X-Mimecast-MFC-AGG-ID: DuTuzjEFNteS6GqyxJJMrg Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2BAD21955D89; Mon, 20 Jan 2025 12:42:40 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.104]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 220E019560A3; Mon, 20 Jan 2025 12:42:35 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jan 2025 13:42:15 +0100 (CET) Date: Mon, 20 Jan 2025 13:42:10 +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: <20250120124209.GB7432@redhat.com> References: <202501201311.6d25a0b9-lkp@intel.com> <20250120121928.GA7432@redhat.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: <20250120121928.GA7432@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Forgot to mention... On 01/20, Oleg Nesterov wrote: > > 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. But I'll recheck this logic once again tomorrow, perhaps I misread pipe_write() when I made this patch. Oleg.