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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 15E8DC0044B for ; Wed, 13 Feb 2019 21:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E5CCA21872 for ; Wed, 13 Feb 2019 21:17:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388390AbfBMVRZ (ORCPT ); Wed, 13 Feb 2019 16:17:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39402 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728060AbfBMVRZ (ORCPT ); Wed, 13 Feb 2019 16:17:25 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7399C72D79; Wed, 13 Feb 2019 21:17:24 +0000 (UTC) Received: from localhost (ovpn-200-19.brq.redhat.com [10.40.200.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 19EEA101E845; Wed, 13 Feb 2019 21:17:21 +0000 (UTC) Date: Wed, 13 Feb 2019 22:17:16 +0100 From: Stefano Brivio To: Eric Dumazet Cc: Stephen Hemminger , netdev@vger.kernel.org, Sabrina Dubroca , David Ahern Subject: Re: [PATCH iproute2 net-next v2 3/4] ss: Buffer raw fields first, then render them as a table Message-ID: <20190213221716.5f958c2a@redhat.com> In-Reply-To: References: <82f1bc98-df6d-2b0a-17e5-fa057563284e@gmail.com> <20190213093711.13ab560e@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 13 Feb 2019 21:17:24 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 13 Feb 2019 09:31:03 -0800 Eric Dumazet wrote: > On 02/13/2019 12:37 AM, Stefano Brivio wrote: > > On Tue, 12 Feb 2019 16:42:04 -0800 > > Eric Dumazet wrote: > > > >> I do not get it. > >> > >> "ss -emoi " uses almost 1KB per socket. > >> > >> 10,000,000 sockets -> we need about 10GB of memory ??? > >> > >> This is a serious regression. > > > > I guess this is rather subjective: the worst case I considered back then > > was the output of 'ss -tei0' (less than 500 bytes) for one million > > sockets, which gives 500M of memory, which should in turn be fine on a > > machine handling one million sockets. > > > > Now, if 'ss -emoi' on 10 million sockets is an actual use case (out of > > curiosity: how are you going to process that output? Would JSON help?), > > I see two easy options to solve this: > > > ss -temoi | parser (written in shell or awk or whatever...) > > This is a use case, I just got bitten because using ss command > actually OOM my container, while trying to debug a busy GFE. > > The host itself can have 10,000,000 TCP sockets, but usually sysadmin shells > run in a container with no more than 500 MB available. > > Otherwise, it would be too easy for a buggy program to OOM the whole machine > and have angry customers. > > > > > 1. flush the output every time we reach a given buffer size (1M > > perhaps). This might make the resulting blocks slightly unaligned, > > with occasional loss of readability on lines occurring every 1k to > > 10k sockets approximately, even though after 1k sockets column sizes > > won't change much (it looks anyway better than the original), and I > > don't expect anybody to actually scroll that output > > > > 2. add a switch for unbuffered output, but then you need to remember to > > pass it manually, and the whole output would be as bad as the > > original in case you need the switch. > > > > I'd rather go with 1., it's easy to implement (we already have partial > > flushing with '--events') and it looks like a good compromise on > > usability. Thoughts? > > > > 1 seems fine, but a switch for 'please do not try to format' would be fine. > > I wonder why we try to 'format' when stdout is a pipe or a regular file . On a second thought: what about | less, or | grep [ports], or > readable.log? I guess those might also be rather common use cases, what do you think? I'm tempted to skip this for the moment and just go with option 1. -- Stefano