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 755E71420DF for ; Wed, 24 Apr 2024 08:15:36 +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=1713946538; cv=none; b=G5rKoaynE9zoGbe1kkJWELoR5ltl2vO0Rpk/0+wdPuNjyk+3yK7ENZjZRZax8EmWBkl6AxWkP6BjdD4KJ5I620Tj3S/RWqjeVS9Ua3z2c7twEhXmYibX7FZXyBtMyvD8WNz6sK6DA7skFuxCEHOyRqO/6/d+cjqaUiWr7jYy4DI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713946538; c=relaxed/simple; bh=t6A7FwupU41uLyUWfgUbQndg5gFkN3irKoyrRmKumQA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JFYA5fgz+HurL8x4P9AsFqMGpBlLazRo+u552GEghbH34qF7WEfwf/juIV/TxNm0GVTZq0+Bat6tWz0idvUvF+y9z+egez53fti04VpTwbsAx8q7udJYiKgGf/2ohILpc45Grkx4LkDfCLKCxU1TGrEx4C8S4pqiBCQONL7KMg0= 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 276DA339; Wed, 24 Apr 2024 01:16:03 -0700 (PDT) Received: from [10.57.74.127] (unknown [10.57.74.127]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 740D73F64C; Wed, 24 Apr 2024 01:15:33 -0700 (PDT) Message-ID: <5edfe6b3-8f00-46c4-8ddb-d1add845541d@arm.com> Date: Wed, 24 Apr 2024 09:15:31 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 5/5] mm: shmem: add anonymous share mTHP counters Content-Language: en-GB To: David Hildenbrand , Baolin Wang , Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, hughd@google.com, willy@infradead.org, wangkefeng.wang@huawei.com, ying.huang@intel.com, shy828301@gmail.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <05d0096e4ec3e572d1d52d33a31a661321ac1551.1713755580.git.baolin.wang@linux.alibaba.com> <140d4efa-28a0-449a-9570-9d44c23b55d1@redhat.com> From: Ryan Roberts In-Reply-To: <140d4efa-28a0-449a-9570-9d44c23b55d1@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 24/04/2024 08:11, David Hildenbrand wrote: > On 24.04.24 08:10, Baolin Wang wrote: >> >> >> On 2024/4/23 19:37, David Hildenbrand wrote: >>> On 23.04.24 03:17, Barry Song wrote: >>>> On Mon, Apr 22, 2024 at 3:03 PM Baolin Wang >>>> wrote: >>>>> >>>>> Signed-off-by: Baolin Wang >>>>> --- >>>>>    include/linux/huge_mm.h | 2 ++ >>>>>    mm/huge_memory.c        | 4 ++++ >>>>>    mm/shmem.c              | 5 ++++- >>>>>    3 files changed, 10 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>>>> index 26b6fa98d8ac..67b9c1acad31 100644 >>>>> --- a/include/linux/huge_mm.h >>>>> +++ b/include/linux/huge_mm.h >>>>> @@ -270,6 +270,8 @@ enum mthp_stat_item { >>>>>           MTHP_STAT_ANON_SWPOUT, >>>>>           MTHP_STAT_ANON_SWPOUT_FALLBACK, >>>>>           MTHP_STAT_ANON_SWPIN_REFAULT, >>>>> +       MTHP_STAT_SHMEM_ANON_ALLOC, >>>>> +       MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK, >>>> >>>> not quite sure about this. for 2MB pmd-mapped THP shmem, we count them >>>> as FILE_THP. >>>> here we are counting as SHMEM_ANON. To me, SHMEM_ANON is more correct but >>>> it doesn't align with pmd-mapped THP. David, Ryan, what do you think? >>> >>> The term "anonymous share" in the patch subject is weird to begin with >>> ;) Easy to confuse with anonymous cow-shared memory. Let's just call it >>> "anonymous shmem", which it is under the hood. >> >> Sure. >> >>> ... regarding the question: if we add FILE_ALLOC and friends, at least >>> initially, we wouldn't account other large pagecache folios. >>> >>> ... likely we should add that then as well so the counter matches the >>> actual name? >>> >>> If we later realize that we need separate FILE vs. SHMEM vs. WHATEVER >>> counters, we can always add more fine-grained counters later. Doing it >>> consistently w.r.t. traditional THPs first sounds reasonable. >> >> Um, once we expose it to userspace through the sysfs interface, the >> sysfs interface should be explicit as much as possible and avoid >> confusing users, otherwise it will be difficult to change this kind of >> interface in the future. Personally, I prefer to Ryan's suggestion. > > Inconsistency is confusing. As long as you avoid that, I don't particularly care. This is a good point. We have been careful to make sure the 2M ANON mTHP stats match the existing PMD-size stats. So we should definitely make sure that any future 2M FILE mTHP stats match too, which I guess means counting both SHMEM and FILE events. So perhaps it makes more sense to add FILE counters to start with. If we need the SHMEM-specific counters, we could add them later? I'm happy to go with the crowd on this...