From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D7C96376EA; Tue, 30 Jan 2024 04:52:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706590356; cv=none; b=oMz8nH17qrj+eNtclkPEaA/dmhBFvTvvcN3G4ArVWY4T46++tPgLhxjd0VGuP9wUaMO6O+SoB8xaVSAel43Y0m1DPb/ut0YuDQsA2hgEgpvWZy8JQawDzXjmhZ+opaf2SlMNHSxL346GSG8QHNucz656II5Z+PqeL78LjpKGfG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706590356; c=relaxed/simple; bh=pSny46fbcm5afdgGkL8N9AZNYoV2BmDZXSWgbG1D29A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UoGenMDxeebLrD+fGkOt6fdpPkhzv+dBI2J3alJpNIvwVikmN38GCWBxvTPAw8aw6FJYx4bjM4EdUQ3akB7hC5RMor6m12RhZoKn3JKOHDJ0BNeO3ya4vXmKlu2fuhSg2RBu8Jb/gZWBixetMFdDqh72Bk5NEZH2ETa3YMz8T14= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 5BB05DA7; Mon, 29 Jan 2024 20:53:11 -0800 (PST) Received: from [10.163.41.110] (unknown [10.163.41.110]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 45BD03F762; Mon, 29 Jan 2024 20:52:15 -0800 (PST) Message-ID: <2cb8288c-5378-4968-a75b-8462b41998c6@arm.com> Date: Tue, 30 Jan 2024 10:22:11 +0530 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 06/35] mm: cma: Make CMA_ALLOC_SUCCESS/FAIL count the number of pages Content-Language: en-US To: Alexandru Elisei 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 References: <20240125164256.4147-1-alexandru.elisei@arm.com> <20240125164256.4147-7-alexandru.elisei@arm.com> <0a71c87a-ae2c-4a61-8adb-3a51d6369b99@arm.com> From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/29/24 17:21, Alexandru Elisei wrote: > 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: That should not be done in CMA which is a generic multi purpose allocator. > (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. I am afraid that might not be enough justification for getting something merged mainline. > > *that would require userspace reading cma_alloc_success and > cma_release_success before any tagged allocations are performed. While assuming that no other non-memory-tagged CMA based allocation amd free call happens in the meantime ? That would be on real thin ice. I suppose arm64 tagged memory specific allocation or free related counters need to be created on the caller side, including arch_free_pages_prepare().