From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 239CA23AD for ; Sat, 13 Jul 2024 04:01:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720843290; cv=none; b=Mx9CRONxgPx8Fe7TT+GiK9/IXiE5gVtwYALUnaYZ6C0xNC7jrZcTvXQylBiP6vUrAqZO9kHPXpC7H5HJda5j25nDwtebABYz6rHeYvwYne4HaBeNYqACpWMEsHBUhOc5OoeRS6K/BCAw6Dreex3wXt5sWHe9Pp3hHSGEpeSnqew= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720843290; c=relaxed/simple; bh=r8Yhpjr5NboO/zGxXvko/WtS4lAmgEOW3o68UTjGljc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=X9ZUfgmG+H/i5L1QqowKR9on+RIFy+RSRPRKoU3dKPF6bCZGLRKZ0LA6wbDwxv7HqTN/i/tyWd4kMk2AD+yIZKR0U3Uwjv3BNOwEY5cg0q09lXyqhIILZ5HK4WfGu0jS2aCuwunYi/VRbNv7aWOzK7FVwNrYF/+7jSuVM0lwjfk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=KplZNKmr; arc=none smtp.client-ip=115.124.30.118 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="KplZNKmr" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1720843280; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=l1zz8KU0ZreEJ+A1Pk7yXjuLTLJQY3EYOHYwky64JnU=; b=KplZNKmrG+nXPNI+Wy5ADQ/yOyOQq9vatrxmyfZODjpcC0EDo/Pok5Cwv8IWRRfsmSwxR3lfKTsj09UWDBepPjtJp8Yu0f0K0au2p82QJJ1EBzhq0ZaEdOcnfvaXP81cGWT7AiBNV4itTX9i7BiynwHurcY8XtRYlPTntdf2UCU= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R841e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037067111;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0WAQ.UFK_1720843278; Received: from 30.120.178.44(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WAQ.UFK_1720843278) by smtp.aliyun-inc.com; Sat, 13 Jul 2024 12:01:19 +0800 Message-ID: Date: Sat, 13 Jul 2024 12:01:17 +0800 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] mm/huge_memory: Avoid PMD-size page cache if needed To: David Hildenbrand , Gavin Shan , Matthew Wilcox Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, william.kucharski@oracle.com, ryan.roberts@arm.com, shan.gavin@gmail.com References: <20240711104840.200573-1-gshan@redhat.com> <63a0364b-a2e0-48c2-b255-e976112deeb1@redhat.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/7/13 09:03, David Hildenbrand wrote: > On 12.07.24 07:39, Gavin Shan wrote: >> On 7/12/24 7:03 AM, David Hildenbrand wrote: >>> On 11.07.24 22:46, Matthew Wilcox wrote: >>>> On Thu, Jul 11, 2024 at 08:48:40PM +1000, Gavin Shan wrote: >>>>> +++ b/mm/huge_memory.c >>>>> @@ -136,7 +136,8 @@ unsigned long __thp_vma_allowable_orders(struct >>>>> vm_area_struct *vma, >>>>>            while (orders) { >>>>>                addr = vma->vm_end - (PAGE_SIZE << order); >>>>> -            if (thp_vma_suitable_order(vma, addr, order)) >>>>> +            if (!(vma->vm_file && order > MAX_PAGECACHE_ORDER) && >>>>> +                thp_vma_suitable_order(vma, addr, order)) >>>>>                    break; >>>> >>>> Why does 'orders' even contain potential orders that are larger than >>>> MAX_PAGECACHE_ORDER? >>>> >>>> We do this at the top: >>>> >>>>           orders &= vma_is_anonymous(vma) ? >>>>                           THP_ORDERS_ALL_ANON : THP_ORDERS_ALL_FILE; >>>> >>>> include/linux/huge_mm.h:#define THP_ORDERS_ALL_FILE >>>> (BIT(PMD_ORDER) | BIT(PUD_ORDER)) >>>> >>>> ... and that seems very wrong.  We support all kinds of orders for >>>> files, not just PMD order.  We don't support PUD order at all. >>>> >>>> What the hell is going on here? >>> >>> yes, that's just absolutely confusing. I mentioned it to Ryan lately >>> that we should clean that up (I wanted to look into that, but am >>> happy if someone else can help). >>> >>> There should likely be different defines for >>> >>> DAX (PMD|PUD) >>> >>> SHMEM (PMD) -- but soon more. Not sure if we want separate ANON_SHMEM >>> for the time being. Hm. But shmem is already handles separately, so >>> maybe we can just ignore shmem here. >>> >>> PAGECACHE (1 .. MAX_PAGECACHE_ORDER) >>> >>> ? But it's still unclear to me. >>> >>> At least DAX must stay special I think, and PAGECACHE should be >>> capped at MAX_PAGECACHE_ORDER. >>> >> >> David, I can help to clean it up. Could you please help to confirm the >> following > > Thanks! > >> changes are exactly what you're suggesting? Hopefully, there are >> nothing I've missed. >> The original issue can be fixed by the changes. With the changes >> applied, madvise(MADV_COLLAPSE) >> returns with errno -22 in the test program. >> >> The fix tag needs to adjusted either. >> >> Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface") >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index 2aa986a5cd1b..45909efb0ef0 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -74,7 +74,12 @@ extern struct kobj_attribute shmem_enabled_attr; >>    /* >>     * Mask of all large folio orders supported for file THP. >>     */ >> -#define THP_ORDERS_ALL_FILE    (BIT(PMD_ORDER) | BIT(PUD_ORDER)) > > DAX doesn't have any MAX_PAGECACHE_ORDER restrictions (like hugetlb). So > this should be > > /* >  * FSDAX never splits folios, so the MAX_PAGECACHE_ORDER limit does not >  * apply here. >  */ > THP_ORDERS_ALL_FILE_DAX ((BIT(PMD_ORDER) | BIT(PUD_ORDER)) > > Something like that > >> +#define THP_ORDERS_ALL_FILE_DAX                \ >> +       ((BIT(PMD_ORDER) | BIT(PUD_ORDER)) & (BIT(MAX_PAGECACHE_ORDER >> + 1) - 1)) >> +#define THP_ORDERS_ALL_FILE_DEFAULT    \ >> +       ((BIT(MAX_PAGECACHE_ORDER + 1) - 1) & ~BIT(0)) >> +#define THP_ORDERS_ALL_FILE            \ >> +       (THP_ORDERS_ALL_FILE_DAX | THP_ORDERS_ALL_FILE_DEFAULT) > > Maybe we can get rid of THP_ORDERS_ALL_FILE (to prevent abuse) and fixup > THP_ORDERS_ALL instead. > >>    /* >>     * Mask of all large folio orders supported for THP. >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 2120f7478e55..4690f33afaa6 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -88,9 +88,17 @@ unsigned long __thp_vma_allowable_orders(struct >> vm_area_struct *vma, >>           bool smaps = tva_flags & TVA_SMAPS; >>           bool in_pf = tva_flags & TVA_IN_PF; >>           bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS; >> +       unsigned long supported_orders; >> + >>           /* Check the intersection of requested and supported orders. */ >> -       orders &= vma_is_anonymous(vma) ? >> -                       THP_ORDERS_ALL_ANON : THP_ORDERS_ALL_FILE; >> +       if (vma_is_anonymous(vma)) >> +               supported_orders = THP_ORDERS_ALL_ANON; >> +       else if (vma_is_dax(vma)) >> +               supported_orders = THP_ORDERS_ALL_FILE_DAX; >> +       else >> +               supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; > > This is what I had in mind. > > But, do we have to special-case shmem as well or will that be handled > correctly? For anonymous shmem, it is now same as anonymous THP, which can utilize THP_ORDERS_ALL_ANON. For tmpfs, we currently only support PMD-sized THP (will support more larger orders in the future). Therefore, I think we can reuse THP_ORDERS_ALL_ANON for shmem now: if (vma_is_anonymous(vma) || shmem_file(vma->vm_file))) supported_orders = THP_ORDERS_ALL_ANON; ......