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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EDD96C47422 for ; Mon, 29 Jan 2024 11:51:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=oxF2d7mQkH1UfjF1FMjKEkQnc5MOFo4datDulTY3nGM=; b=g/iQK1Z/ZS1/Hq ODUcXsbtFEjO9B9ecJKXKDhLYllAwJszUtLo6MuDo0HVhg56tMliT45Deb7wD8F1jhaLjoZ52x45w yJdcxPm8D6Qrx6tZDDviUJtg/E9eHIVZ4db/aQd1sFdLat1YHS4fBgUzWwW8huW6yG8l27t6psWdc HAa/HseOhgLEED0nKzGxkoXLn47RhBb75DEdaAQvrtXwY4hNnl3tlGBWkKkk//hQNngZWXmOXFSCJ n7cE4NQUkWd6JzZtxQj/76jNfZCkalR26e4bnBV8Pi4y93ymfyR4q8XXnOa2zC+tbkXsu/Wcp4BCW 9s24MIWulV1OXAMzeYfA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rUQAx-0000000CSzr-17AP; Mon, 29 Jan 2024 11:51:43 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rUQAu-0000000CSxf-0g4M for linux-arm-kernel@lists.infradead.org; Mon, 29 Jan 2024 11:51:41 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7D31E1FB; Mon, 29 Jan 2024 03:52:22 -0800 (PST) Received: from raptor (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 407943F5A1; Mon, 29 Jan 2024 03:51:33 -0800 (PST) Date: Mon, 29 Jan 2024 11:51:30 +0000 From: Alexandru Elisei To: Anshuman Khandual Cc: catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com, pcc@google.com, steven.price@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH RFC v3 06/35] mm: cma: Make CMA_ALLOC_SUCCESS/FAIL count the number of pages Message-ID: References: <20240125164256.4147-1-alexandru.elisei@arm.com> <20240125164256.4147-7-alexandru.elisei@arm.com> <0a71c87a-ae2c-4a61-8adb-3a51d6369b99@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0a71c87a-ae2c-4a61-8adb-3a51d6369b99@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240129_035140_393836_40F12D1A X-CRM114-Status: GOOD ( 26.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: > > > On 1/25/24 22:12, Alexandru Elisei wrote: > > The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one > > after each cma_alloc() function call. This is done even though cma_alloc() > > can allocate an arbitrary number of CMA pages. When looking at > > /proc/vmstat, the number of successful (or failed) cma_alloc() calls > > doesn't tell much with regards to how many CMA pages were allocated via > > cma_alloc() versus via the page allocator (regular allocation request or > > PCP lists refill). > > > > This can also be rather confusing to a user who isn't familiar with the > > code, since the unit of measurement for nr_free_cma is the number of pages, > > but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() > > function calls. > > > > Let's make this consistent, and arguably more useful, by having > > CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and > > CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to > > allocate. > > > > For users that wish to track the number of cma_alloc() calls, there are > > tracepoints for that already implemented. > > > > Signed-off-by: Alexandru Elisei > > --- > > mm/cma.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/cma.c b/mm/cma.c > > index f49c95f8ee37..dbf7fe8cb1bd 100644 > > --- a/mm/cma.c > > +++ b/mm/cma.c > > @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, > > pr_debug("%s(): returned %p\n", __func__, page); > > out: > > if (page) { > > - count_vm_event(CMA_ALLOC_SUCCESS); > > + count_vm_events(CMA_ALLOC_SUCCESS, count); > > cma_sysfs_account_success_pages(cma, count); > > } else { > > - count_vm_event(CMA_ALLOC_FAIL); > > + count_vm_events(CMA_ALLOC_FAIL, count); > > if (cma) > > cma_sysfs_account_fail_pages(cma, count); > > } > > Without getting into the merits of this patch - which is actually trying to do > semantics change to /proc/vmstat, wondering how is this even related to this > particular series ? If required this could be debated on it's on separately. Having the number of CMA pages allocated and the number of CMA pages freed allows someone to infer how many tagged pages are in use at a given time: (allocated CMA pages - CMA pages allocated by drivers* - CMA pages released) * 32. That is valuable information for software and hardware designers. Besides that, for every iteration of the series, this has proven invaluable for discovering bugs with freeing and/or reserving tag storage pages. *that would require userspace reading cma_alloc_success and cma_release_success before any tagged allocations are performed. Thanks, Alex _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel