From owner-dev-commits-src-all@freebsd.org Thu Mar 11 19:20:26 2021 Return-Path: Delivered-To: dev-commits-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 2309A5AAD83; Thu, 11 Mar 2021 19:20:26 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (turbocat.net [88.99.82.50]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4DxJgY6xqDz3nSn; Thu, 11 Mar 2021 19:20:25 +0000 (UTC) (envelope-from hps@selasky.org) Received: from hps2020.home.selasky.org (unknown [178.17.145.105]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id 50C662601F5; Thu, 11 Mar 2021 20:20:24 +0100 (CET) Subject: Re: git: d1cbe7908986 - main - Allocating the LinuxKPI current structure from an interrupt thread must be done using the M_NOWAIT flag after 1ae20f7c70ea . To: Konstantin Belousov Cc: John Baldwin , src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org References: <202103100952.12A9qRKR040117@gitrepo.freebsd.org> <2b1739ab-000c-ca28-5a59-0a3e19ef4591@selasky.org> <5aaa5f2a-a67d-a495-7f56-a6b31c2494c7@FreeBSD.org> <3dcd63b0-fe90-2855-f349-2117ca4b6b26@selasky.org> From: Hans Petter Selasky Message-ID: <8fe37b5e-29a7-ffeb-fddb-3b31a6e79ab0@selasky.org> Date: Thu, 11 Mar 2021 20:20:05 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4DxJgY6xqDz3nSn X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-BeenThere: dev-commits-src-all@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for all branches of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Mar 2021 19:20:26 -0000 On 3/11/21 8:04 PM, Konstantin Belousov wrote: > On Thu, Mar 11, 2021 at 07:41:53PM +0100, Hans Petter Selasky wrote: >> On 3/11/21 7:35 PM, Konstantin Belousov wrote: >>> And I dislike this. It is yet another case of introducing consumer-specific >>> logic into core. Isn't netepoch example enough? >>> >>> I presented another patch to Hans, where task and mm allocations are >>> switched to zones, and the zones have reserve applied. Then allocations >>> from ithreads use the reserve. >>> >>> There is one detail there, reserve is finite, for x86 I set it to the >>> total limit of interrupts. This somewhat breaks if interrupts are >>> deallocated and reallocated, but I think it is good enough even with >>> this wart. >> >> Hi, >> >> Your patch doesn't address the issue of initializing the pointers in >> question once. Still, for every call, we need to check if the pointer is >> valid. This is not neccessary. > I do not understand what you are saying there. > Which pointers? How does it not address? Hi, The current code calls linux_set_current() for every interrupt and timer callback. That means we continue to check td_lkpi_task for NULL for every one of these calls. Not strictly needed. > >> >> Also I don't see why we need to create a own UMA zone for these simple >> structures. Won't the per-CPU sysctl consume more memory than the actual >> task structures being allocated? > Dedicated UMA zone allows to gracefully solve the requirement of non-failing > allocation in non-sleepable context. This is much simpler and cleaner than > either trying to enumerate all existing ithreads or adding consumer-specific > controls into generic kernel facility. > Maybe I'm new to UMA zones. The M_USE_RESERVE can also be used with malloc() ? --HPS