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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4ECA1C43334 for ; Thu, 7 Jul 2022 16:20:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235967AbiGGQUf (ORCPT ); Thu, 7 Jul 2022 12:20:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60194 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235881AbiGGQUe (ORCPT ); Thu, 7 Jul 2022 12:20:34 -0400 Received: from mail-vs1-xe2c.google.com (mail-vs1-xe2c.google.com [IPv6:2607:f8b0:4864:20::e2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 043EB25EAF for ; Thu, 7 Jul 2022 09:20:34 -0700 (PDT) Received: by mail-vs1-xe2c.google.com with SMTP id 189so18794164vsh.2 for ; Thu, 07 Jul 2022 09:20:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Ci6aP7nKVQUaHARVmSRnYm57qnA3hBbkbfQkbvG0XxM=; b=bn2LAVeJrnwPGUJTR23aVQd2z1NTOuHTvpU/tYSYxdlwQuROcEQ3mFWTjFuR/eT9bz kOmuNckX3qdC7gTX86kUSMLc6ba6opfm5k4s8kIQPVFordq1Y8xDfPcR/yIE4vdjn1di nsxdWsPC0KBppiVaq34zd4k25zNJtoGIi/zZlu+PcrYCHpnMeLxpFHYFmM7BTP/0DFl5 Wef945ienMtpNZsusurRYwMMfHESj7SYZ2z1J1QHb2k7ijZGQmdiT8o0IHVAFaBQtbM5 AcZCaF1YddU4OgOsUBFxmCL9FGzfb7czqj4kPJ4MD/nQ1VJmCg9WZcUZrTDbkX4qf3+F 4b8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Ci6aP7nKVQUaHARVmSRnYm57qnA3hBbkbfQkbvG0XxM=; b=8JxU0nb/SLsmOz7KoUuD9AzcdHS0R09L9PWHAXp9VWIB/Lneym6zShewWO8sEWk0nh vJbUbAy+7mWpz437E2lTtMzxpC41egPnYywTrad3m9NkbrXBH8bCgA/YRc2N2KaNbJGW 4CXQvnN1Xl834rm7foeg5fT5zGU2JXqhqvM3bzEwF9HQ/b00bbqZW7luMVZGUPcfc8+i u3FKrFQIdrl1PZGGpYiUcc/0LCjTH2Dc4N2clsPaACfdR4nu+XEx+Kyc3zEcS5cgOhi7 0sZ3dbub7OdedLcJc0e2zXjk2fMnof/2ylLkq+Vgyqc4R+hZfO0L3vw+o9nSZITUxHX3 vlmA== X-Gm-Message-State: AJIora8doFV/WELO/xFV/ktfsB758Ujt48/7f90DlkQCDcVrO6eHLzLx WB/KOm3Pd3Ezy+q5XbuWUnxQwG1ONiUHCeenqxU= X-Google-Smtp-Source: AGRyM1vEEck/CSTfqPPPCywcusjE/F0df+gWYrSoMQDaMK9O8h1v3u4YxUY9WEwcXcYOwfz537RsgK/t4A36exmbZYA= X-Received: by 2002:a67:1945:0:b0:355:ab65:9db3 with SMTP id 66-20020a671945000000b00355ab659db3mr27849908vsz.22.1657210833074; Thu, 07 Jul 2022 09:20:33 -0700 (PDT) MIME-Version: 1.0 References: <20220706155848.4939-1-laoar.shao@gmail.com> <20220706155848.4939-2-laoar.shao@gmail.com> <20220707000721.dtl356trspb23ctp@google.com> In-Reply-To: From: Yafang Shao Date: Fri, 8 Jul 2022 00:19:56 +0800 Message-ID: Subject: Re: [PATCH bpf-next v2 1/2] bpf: Make non-preallocated allocation low priority To: Alexei Starovoitov Cc: Shakeel Butt , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , Quentin Monnet , Roman Gushchin , Hao Luo , bpf , Linux MM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Jul 7, 2022 at 11:44 PM Alexei Starovoitov wrote: > > On Thu, Jul 7, 2022 at 3:28 AM Yafang Shao wrote: > > > > On Thu, Jul 7, 2022 at 8:07 AM Shakeel Butt wrote: > > > > > > On Wed, Jul 06, 2022 at 03:58:47PM +0000, Yafang Shao wrote: > > > > GFP_ATOMIC doesn't cooperate well with memcg pressure so far, especially > > > > if we allocate too much GFP_ATOMIC memory. For example, when we set the > > > > memcg limit to limit a non-preallocated bpf memory, the GFP_ATOMIC can > > > > easily break the memcg limit by force charge. So it is very dangerous to > > > > use GFP_ATOMIC in non-preallocated case. One way to make it safe is to > > > > remove __GFP_HIGH from GFP_ATOMIC, IOW, use (__GFP_ATOMIC | > > > > __GFP_KSWAPD_RECLAIM) instead, then it will be limited if we allocate > > > > too much memory. > > > > > > Please use GFP_NOWAIT instead of (__GFP_ATOMIC | __GFP_KSWAPD_RECLAIM). > > > There is already a plan to completely remove __GFP_ATOMIC and mm-tree > > > already have a patch for that. > > > > > > > After reading the discussion[1], it looks good to me to use GFP_NOWAIT > > instead. I will update it. > > Should we use GFP_ATOMIC | __GFP_NOMEMALLOC instead > to align with its usage in the networking stack? GFP_ATOMIC | __GFP_NOMEMALLOC will continue to break the memcg limit, so we have to modify the try_charge_memcg() code to make sure __GFP_NOMEMALLOC takes precedence over the __GFP_HIGH flag, IOW, if both of them are set we won't allow it to break memcg limit. That will need more verification. -- Regards Yafang