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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F0BAC43334 for ; Wed, 6 Jul 2022 18:31:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E99B56B0072; Wed, 6 Jul 2022 14:31:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E48806B0073; Wed, 6 Jul 2022 14:31:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D37396B0074; Wed, 6 Jul 2022 14:31:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id C23EE6B0072 for ; Wed, 6 Jul 2022 14:31:50 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 910B980DC1 for ; Wed, 6 Jul 2022 18:31:50 +0000 (UTC) X-FDA: 79657518780.28.49E4782 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf26.hostedemail.com (Postfix) with ESMTP id 435D614003D for ; Wed, 6 Jul 2022 18:31:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=f9Ii8tE/pObkkb4aqdBkut0D7NLGv6JCUxdmC2yBlGs=; b=otFVN+yBMpofUtTDojp391cjDf Gf8ovL4zYi98td5/7hPyIAn1p6KRRAQt1j5yx4JUvL0uc0gU2Opv014Abgc6DOfWH45lJixkv1NRr Sd+bRSVnxoaamdXph8tZ0k2EhsIxjNGChNsi4ZGdu5L05oPpxyiHTdnUf3vqKlBaZJ+VoDb+nQHo3 P91DcF1PRpJnIl/cSXDk9Yxz/3BCEghGFeKP+Zw54eaJ67y8A91mW86moVCFJXNC5uj21VlR9TIC2 KXu5ZfrnyWItObkTGJ1dgbZSTJKAGiiQyvewCEsZHuwEMTSF8A+BnTS29vIC7fFmPN/mPhhgLligR pYoAXf5w==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o99oE-001s9f-3o; Wed, 06 Jul 2022 18:31:34 +0000 Date: Wed, 6 Jul 2022 19:31:34 +0100 From: Matthew Wilcox To: Alexei Starovoitov Cc: Christoph Hellwig , davem@davemloft.net, daniel@iogearbox.net, andrii@kernel.org, tj@kernel.org, kafai@fb.com, bpf@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka Subject: Re: [PATCH bpf-next 0/5] bpf: BPF specific memory allocator. Message-ID: References: <20220623003230.37497-1-alexei.starovoitov@gmail.com> <20220706175034.y4hw5gfbswxya36z@MacBook-Pro-3.local> <20220706180525.ozkxnbifgd4vzxym@MacBook-Pro-3.local.dhcp.thefacebook.com> <20220706182635.ccgt6zcr6bkd3rjc@MacBook-Pro-3.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220706182635.ccgt6zcr6bkd3rjc@MacBook-Pro-3.local> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657132310; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=f9Ii8tE/pObkkb4aqdBkut0D7NLGv6JCUxdmC2yBlGs=; b=Edi0fQLOXiXUfRUnbNLaF+3k5jOQX72D245nEEM741Iyvvg7uRoqj9er9yMAwQRH2HfI9w lZcTIQCbXH0jRcr5LOfyPOLH0mIoP5oA1K4upgdqhywVcHffDsUA0eGHs6Zyo/6I+PF6yE t9KY0lN96XBlP+UuSKProrMD8xyu/Bc= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657132310; a=rsa-sha256; cv=none; b=lhDJWjzgreyJ+WFIFM6iNSIxHbtAdYk3fcwofgGLP2LWk3nyOBdixFcb/CXlo8Pf/36nVY VKx82MlApcPkR2Rj5OmcD9Nsq+kX/2pX5eTJ0lXqPc7nZUrUDULJF5nq7sGKTsJsalHNtI 03cMZ/R3+6QsEzmUAB49xZHdLRfUK+c= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=otFVN+yB; dmarc=none; spf=none (imf26.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspam-User: Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=otFVN+yB; dmarc=none; spf=none (imf26.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 435D614003D X-Stat-Signature: kn5s9zzcrkgjdqjyjjcyuiai53niwrrj X-HE-Tag: 1657132310-164128 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jul 06, 2022 at 11:26:35AM -0700, Alexei Starovoitov wrote: > On Wed, Jul 06, 2022 at 07:21:29PM +0100, Matthew Wilcox wrote: > > On Wed, Jul 06, 2022 at 11:05:25AM -0700, Alexei Starovoitov wrote: > > > On Wed, Jul 06, 2022 at 06:55:36PM +0100, Matthew Wilcox wrote: > > > > For example, I assume that a BPF program > > > > has a fairly tight limit on how much memory it can cause to be allocated. > > > > Right? > > > > > > No. It's constrained by memcg limits only. It can allocate gigabytes. > > > > I'm confused. A BPF program is limited to executing 4096 insns and > > using a maximum of 512 bytes of stack space, but it can allocate an > > unlimited amount of heap? That seems wrong. > > 4k insn limit was lifted years ago. You might want to update the documentation. https://www.kernel.org/doc/html/latest/bpf/bpf_design_QA.html still says 4096. > bpf progs are pretty close to be at parity with kernel modules. > Except that they are safe, portable, and users have full visibility into them. > It's not a blob of bytes unlike .ko. It doesn't seem unreasonable to expect them to behave like kernel modules, then. If they want to allocate memory in NMI context, then they should get to preallocate it before they go into NMI context.