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Thu, 01 Sep 2022 07:41:05 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (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 noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B9A783004C7; Thu, 1 Sep 2022 09:41:02 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 925E52B871FC0; Thu, 1 Sep 2022 09:41:02 +0200 (CEST) Date: Thu, 1 Sep 2022 09:41:02 +0200 From: Peter Zijlstra To: Kent Overstreet Cc: Mel Gorman , Suren Baghdasaryan , akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, void@manifault.com, juri.lelli@redhat.com, ldufour@linux.ibm.com, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, changbin.du@intel.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, arnd@arndb.de, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-mm@kvack.org, iommu@lists.linux.dev, kasan-dev@googlegroups.com, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 10/30] mm: enable page allocation tagging for __get_free_pages and alloc_pages Message-ID: References: <20220830214919.53220-1-surenb@google.com> <20220830214919.53220-11-surenb@google.com> <20220831101103.fj5hjgy3dbb44fit@suse.de> <20220831174629.zpa2pu6hpxmytqya@moria.home.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220831174629.zpa2pu6hpxmytqya@moria.home.lan> ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b="JPARXCy/"; spf=none (imf04.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.92.199) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662018100; a=rsa-sha256; cv=none; b=Wx/QiooUaK7zY1v6SRimSlIBEhtPD1r9CY7pyR3N0WCa5PQ+eYlgQ6aGga3eH2ErXZCRhW k7HRkqWWkafmQl1AZG8XOqHpaMWnfZXIjYPavAl6MfONjo7Kq04uH95fhlL3lDztZM6hZ6 MOmfDPuD5UHTcVN9pwjGZ3wMVAh+yjU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662018100; 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=qqD5irythXcXnrZi3fFnP54DNBcaxZAOs7bCGWArgiE=; b=YhtUMt1zVt9/1GPu9EXyQ7tKII+4xXa3WMhRrkfRp6CzZT7WkrtGywHP0JjIdiFnGGkVJJ PwBV+1yEz2ZKhJZUprcIrZpgaNR34ZmCkwLHFsWe31Z1tZ0nltNpbWiV5xqRIbVkTWx80A vYC1CYEW11A9cqPdoPPjR6ixqo1muZI= X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E6F394004D X-Rspam-User: Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b="JPARXCy/"; spf=none (imf04.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.92.199) smtp.mailfrom=peterz@infradead.org; dmarc=none X-Stat-Signature: 8sckeobpq18dc1jxngpjqcyag7n6ctct X-HE-Tag: 1662018099-323365 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, Aug 31, 2022 at 01:46:29PM -0400, Kent Overstreet wrote: > Because all the counters are statically allocated, without even a pointer deref > to get to them in the allocation path (one pointer deref to get to them in the > deallocate path), that makes this _much, much_ cheaper than anything that could > be done with tracing - cheap enough that I expect many users will want to enable > it in production. You're contributing to death-by-a-thousand-cuts here. By making all this unconditional you're putting distros in a bind. Most of their users will likely not care about this, but if they enable it, they'll still pay the price for having it. Even static counters will have cache misses etc.. So yes, for the few people that actually care about this stuff, this might be a bit faster, but IMO it gets the econimics all backwards, you're making everybody pay the price instead of only those that care. Also note that you can have your tracepoint based handler have statically allocated data just fine.