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 6B58213212B for ; Mon, 1 Jul 2024 10:16:23 +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=1719828985; cv=none; b=d77C93LIBLHapXBtRbmugJtOaHt60h+rmZ4vOlEetXBGNbHmLH65saspPlvko8TN60s/JAxrV8ydaIh8vW9+ylDQR9m4RgVmYM3OEYrMng+4OFp1kP+qgbOfcLgRNoObhjysy3G16HWj4kx8rfgkcT+Td4FEiKSkIMQ+kMIE5Nk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719828985; c=relaxed/simple; bh=AVpoZSq4XbU+qoRDWyL3ldhMOO3y7kTcuiSrumI5730=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=J/7MadG6TdBNAKt/eeCPid3vRPSbqvzMpZziTQpYSesm951wFrky8Qum6Fm/IIkR/47NHv4mPidCSaCl6ra8Ccee3iaUr3w56Qv4t1zCPPflq7U6DYzWX4po1zFQ/g8fg6g/vfCf+5i2JRVY//Juyic+SSU+eBI6jIb+K/wvOzo= 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 790FC339; Mon, 1 Jul 2024 03:16:47 -0700 (PDT) Received: from [10.57.72.41] (unknown [10.57.72.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 18A333F762; Mon, 1 Jul 2024 03:16:20 -0700 (PDT) Message-ID: <429f2873-8532-4cc8-b0e1-1c3de9f224d9@arm.com> Date: Mon, 1 Jul 2024 11:16:19 +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: [PATCH] support "THPeligible" semantics for mTHP with anonymous shmem Content-Language: en-GB To: David Hildenbrand , Baolin Wang , Bang Li , hughd@google.com, akpm@linux-foundation.org Cc: wangkefeng.wang@huawei.com, ziy@nvidia.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240628104926.34209-1-libang.li@antgroup.com> <4b38db15-0716-4ffb-a38b-bd6250eb93da@arm.com> <4d54880e-03f4-460a-94b9-e21b8ad13119@linux.alibaba.com> <516aa6b3-617c-4642-b12b-0c5f5b33d1c9@arm.com> <597ac51e-3f27-4606-8647-395bb4e60df4@redhat.com> <6f68fb9d-3039-4e38-bc08-44948a1dae4d@arm.com> <992cdbf9-80df-4a91-aea6-f16789c5afd7@redhat.com> <2e0a1554-d24f-4d0d-860b-0c2cf05eb8da@arm.com> <06c74db8-4d10-4a41-9a05-776f8dca7189@redhat.com> From: Ryan Roberts In-Reply-To: <06c74db8-4d10-4a41-9a05-776f8dca7189@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 01/07/2024 10:17, David Hildenbrand wrote: > On 01.07.24 11:14, Ryan Roberts wrote: >> On 01/07/2024 09:57, David Hildenbrand wrote: >>> On 01.07.24 10:50, Ryan Roberts wrote: >>>> On 01/07/2024 09:48, David Hildenbrand wrote: >>>>> On 01.07.24 10:40, Ryan Roberts wrote: >>>>>> On 01/07/2024 09:33, Baolin Wang wrote: >>>>>>> >>>>>>> >>>>>>> On 2024/7/1 15:55, Ryan Roberts wrote: >>>>>>>> On 28/06/2024 11:49, Bang Li wrote: >>>>>>>>> After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for >>>>>>>>> anonymous shmem"), we can configure different policies through >>>>>>>>> the multi-size THP sysfs interface for anonymous shmem. But >>>>>>>>> currently "THPeligible" indicates only whether the mapping is >>>>>>>>> eligible for allocating THP-pages as well as the THP is PMD >>>>>>>>> mappable or not for anonymous shmem, we need to support semantics >>>>>>>>> for mTHP with anonymous shmem similar to those for mTHP with >>>>>>>>> anonymous memory. >>>>>>>>> >>>>>>>>> Signed-off-by: Bang Li >>>>>>>>> --- >>>>>>>>>      fs/proc/task_mmu.c      | 10 +++++++--- >>>>>>>>>      include/linux/huge_mm.h | 11 +++++++++++ >>>>>>>>>      mm/shmem.c              |  9 +-------- >>>>>>>>>      3 files changed, 19 insertions(+), 11 deletions(-) >>>>>>>>> >>>>>>>>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >>>>>>>>> index 93fb2c61b154..09b5db356886 100644 >>>>>>>>> --- a/fs/proc/task_mmu.c >>>>>>>>> +++ b/fs/proc/task_mmu.c >>>>>>>>> @@ -870,6 +870,7 @@ static int show_smap(struct seq_file *m, void *v) >>>>>>>>>      { >>>>>>>>>          struct vm_area_struct *vma = v; >>>>>>>>>          struct mem_size_stats mss = {}; >>>>>>>>> +    bool thp_eligible; >>>>>>>>>            smap_gather_stats(vma, &mss, 0); >>>>>>>>>      @@ -882,9 +883,12 @@ static int show_smap(struct seq_file *m, void >>>>>>>>> *v) >>>>>>>>>            __show_smap(m, &mss, false); >>>>>>>>>      -    seq_printf(m, "THPeligible:    %8u\n", >>>>>>>>> -           !!thp_vma_allowable_orders(vma, vma->vm_flags, >>>>>>>>> -               TVA_SMAPS | TVA_ENFORCE_SYSFS, THP_ORDERS_ALL)); >>>>>>>>> +    thp_eligible = !!thp_vma_allowable_orders(vma, vma->vm_flags, >>>>>>>>> +                        TVA_SMAPS | TVA_ENFORCE_SYSFS, THP_ORDERS_ALL); >>>>>>>>> +    if (vma_is_anon_shmem(vma)) >>>>>>>>> +        thp_eligible = >>>>>>>>> !!shmem_allowable_huge_orders(file_inode(vma->vm_file), >>>>>>>>> +                            vma, vma->vm_pgoff, thp_eligible); >>>>>>>> >>>>>>>> Afraid I haven't been following the shmem mTHP support work as much as I >>>>>>>> would >>>>>>>> have liked, but is there a reason why we need a separate function for >>>>>>>> shmem? >>>>>>> >>>>>>> Since shmem_allowable_huge_orders() only uses shmem specific logic to >>>>>>> determine >>>>>>> if huge orders are allowable, there is no need to complicate the >>>>>>> thp_vma_allowable_orders() function by adding more shmem related logic, >>>>>>> making >>>>>>> it more bloated. In my view, providing a dedicated helper >>>>>>> shmem_allowable_huge_orders(), specifically for shmem, simplifies the logic. >>>>>> >>>>>> My point was really that a single interface (thp_vma_allowable_orders) >>>>>> should be >>>>>> used to get this information. I have no strong opinon on how the >>>>>> implementation >>>>>> of that interface looks. What you suggest below seems perfectly reasonable >>>>>> to me. >>>>> >>>>> Right. thp_vma_allowable_orders() might require some care as discussed in >>>>> other >>>>> context (cleanly separate dax and shmem handling/orders). But that would be >>>>> follow-up cleanups. >>>> >>>> Are you planning to do that, or do you want me to send a patch? >>> >>> I'm planning on looking into some details, especially the interaction with large >>> folios in the pagecache. I'll let you know once I have a better idea what >>> actually should be done :) >> >> OK great - I'll scrub it from my todo list... really getting things done today :) > > Resolved the khugepaged thiny already? :P > > [khugepaged not active when only enabling the sub-size via the 2M folder IIRC] Hmm... baby brain? Sorry about that. I've been a bit useless lately. For some reason it wasn't on my list, but its there now. Will prioritise it, because I agree it's not good.