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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 F27AAC433DB for ; Mon, 29 Mar 2021 07:46:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 581A2601FD for ; Mon, 29 Mar 2021 07:46:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 581A2601FD Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AB3596B0074; Mon, 29 Mar 2021 03:46:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A63B26B0075; Mon, 29 Mar 2021 03:46:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8DDBC6B0078; Mon, 29 Mar 2021 03:46:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0158.hostedemail.com [216.40.44.158]) by kanga.kvack.org (Postfix) with ESMTP id 6F6026B0074 for ; Mon, 29 Mar 2021 03:46:48 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3284C180AD82F for ; Mon, 29 Mar 2021 07:46:48 +0000 (UTC) X-FDA: 77972130096.10.9EA0F5F Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf26.hostedemail.com (Postfix) with ESMTP id 5FF3140002D2 for ; Mon, 29 Mar 2021 07:46:45 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1617004006; h=from:from:reply-to: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=E4a2jyIpz8nOytOLiHN/bRf2rXhs6J4Qg28YA4GgVXg=; b=M+jGBwpI96doNvo22z45CvBY/TPT/ppfA65MKNcF4tZqJfvN3vas6fmkhiE0XU4+UH4NI4 zIkHvSiAbEnptQizzrwq5t9wNeXr19+dyfZ0RNe/Sw72oWsiHRSnRMLTFYEHIE/AEefAnt fCMcWcRs8eYOfx9ieCQWscYFpPQjQ/E= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6D7E5AEA6; Mon, 29 Mar 2021 07:46:46 +0000 (UTC) Date: Mon, 29 Mar 2021 09:46:42 +0200 From: Michal Hocko To: Mike Kravetz Cc: Roman Gushchin , Minchan Kim , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt , Oscar Salvador , Muchun Song , David Rientjes , Miaohe Lin , Peter Zijlstra , Matthew Wilcox , HORIGUCHI NAOYA , "Aneesh Kumar K . V" , Waiman Long , Peter Xu , Mina Almasry , Hillf Danton , Andrew Morton , Joonsoo Kim Subject: Re: [PATCH 1/8] mm: cma: introduce cma_release_nowait() Message-ID: References: <20210325002835.216118-1-mike.kravetz@oracle.com> <20210325002835.216118-2-mike.kravetz@oracle.com> <76aaf359-9496-04df-a585-3662d0375749@oracle.com> <4bc3c5d8-f1a7-6439-8fee-582364a7c021@redhat.com> <0f7f3c4e-530a-5cd2-2719-259e509366e4@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0f7f3c4e-530a-5cd2-2719-259e509366e4@oracle.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 5FF3140002D2 X-Stat-Signature: cxrcwx6e17xnu1g89rcti5nh9nf3uknf Received-SPF: none (suse.com>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617004005-653713 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 Fri 26-03-21 14:32:01, Mike Kravetz wrote: [...] > - Just change the mutex to an irq safe spinlock. Yes please. > AFAICT, the potential > downsides could be: > - Interrupts disabled during long bitmap scans How large those bitmaps are in practice? > - Wasted cpu cycles (spinning) if there is much contention on lock > Both of these would be more of an issue on small/embedded systems. I > took a quick look at the callers of cma_alloc/cma_release and nothing > stood out that could lead to high degrees of contention. However, I > could have missed something. If this is really a practical concern then we can try a more complex solution based on some data. -- Michal Hocko SUSE Labs