From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) (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 84B0D137772 for ; Wed, 13 Nov 2024 03:07:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.100 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731467249; cv=none; b=PR/J3xUc4/HxdRC5zDFZsuiPdlTwPRe4RL20bXinCDyRUM3rrJo8eQZbEWjYouVArGFEl4Otn9I6Ya1MG9qEQI6Ar3Zdbc4lNNntfpBx64NvUKwjBDki0vQXn78eun6mXILvBeGlkqvlW4U+ihV2RSa8nJ4n1XD5oJv1ZU33KpA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731467249; c=relaxed/simple; bh=2kvly/XMrrvf4xxkpYg1RHMOmt6QNShJuLv/Cc5mGTs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TCuh99dAk1MWANvaq3tXohYkevmeYg7Md7CvdgvkdXotqEv1jN35IIeoRrqCRqTPQYsdVqb5qVI3rvSOV9vkXWj24MOkt64ouwCzZSUq5ABoaNsBB8c0KyznjAN4Nuaw6D4BAQtk0SDqj/y0olQ5OtESygRBGGz0mYaPa8xW2mU= 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=hEHCOuem; arc=none smtp.client-ip=115.124.30.100 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="hEHCOuem" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1731467243; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=Pbwpp087l87MJTWrl2ZjKKwDd9bxrq6hIeN+3zWIEJU=; b=hEHCOuemdq1B+T2DlE8DE3MDuG4wB+htw8HBhwmTY54k6t4k1Bmh13ZNRkKK2waFyyDfHB9GyhznG2YIy/ueddyPr2y3DwXQLMX8eb5zlHCI8irM2G59Wc77TwTgun5TkEfz5t/70XOlE3nLzcoTf+vN12LRCgskH41UaixLA7k= Received: from 30.74.144.126(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WJJYp56_1731467240 cluster:ay36) by smtp.aliyun-inc.com; Wed, 13 Nov 2024 11:07:21 +0800 Message-ID: <6c2c25b7-3929-4d1c-8312-61a69f2c5b26@linux.alibaba.com> Date: Wed, 13 Nov 2024 11:07:20 +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 v2 3/5] mm: shmem: add large folio support for tmpfs To: David Hildenbrand , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ryan.roberts@arm.com, ioworker0@gmail.com, da.gomez@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/11/13 00:19, David Hildenbrand wrote: > On 12.11.24 08:45, Baolin Wang wrote: >> Add large folio support for tmpfs write and fallocate paths matching the >> same high order preference mechanism used in the iomap buffered IO path >> as used in __filemap_get_folio(). >> >> Add shmem_mapping_size_orders() to get a hint for the orders of the folio >> based on the file size which takes care of the mapping requirements. >> >> Traditionally, tmpfs only supported PMD-sized huge folios. However >> nowadays >> with other file systems supporting any sized large folios, and extending >> anonymous to support mTHP, we should not restrict tmpfs to allocating >> only >> PMD-sized huge folios, making it more special. Instead, we should allow >> tmpfs can allocate any sized large folios. >> >> Considering that tmpfs already has the 'huge=' option to control the huge >> folios allocation, we can extend the 'huge=' option to allow any sized >> huge >> folios. The semantics of the 'huge=' mount option are: >> >> huge=never: no any sized huge folios >> huge=always: any sized huge folios >> huge=within_size: like 'always' but respect the i_size >> huge=advise: like 'always' if requested with fadvise()/madvise() >> >> Note: for tmpfs mmap() faults, due to the lack of a write size hint, >> still >> allocate the PMD-sized huge folios if huge=always/within_size/advise >> is set. >> >> Moreover, the 'deny' and 'force' testing options controlled by >> '/sys/kernel/mm/transparent_hugepage/shmem_enabled', still retain the >> same >> semantics. The 'deny' can disable any sized large folios for tmpfs, while >> the 'force' can enable PMD sized large folios for tmpfs. >> >> Co-developed-by: Daniel Gomez >> Signed-off-by: Daniel Gomez >> Signed-off-by: Baolin Wang >> --- >>   mm/shmem.c | 91 +++++++++++++++++++++++++++++++++++++++++++++--------- >>   1 file changed, 77 insertions(+), 14 deletions(-) >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 86b2e417dc6f..a3203cf8860f 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -549,10 +549,50 @@ static bool shmem_confirm_swap(struct >> address_space *mapping, >>   static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER; >> +/** >> + * shmem_mapping_size_orders - Get allowable folio orders for the >> given file size. >> + * @mapping: Target address_space. >> + * @index: The page index. >> + * @write_end: end of a write, could extend inode size. >> + * >> + * This returns huge orders for folios (when supported) based on the >> file size >> + * which the mapping currently allows at the given index. The index >> is relevant >> + * due to alignment considerations the mapping might have. The >> returned order >> + * may be less than the size passed. >> + * >> + * Return: The orders. >> + */ >> +static inline unsigned int >> +shmem_mapping_size_orders(struct address_space *mapping, pgoff_t >> index, loff_t write_end) >> +{ >> +    unsigned int order; >> +    size_t size; >> + >> +    if (!mapping_large_folio_support(mapping) || !write_end) >> +        return 0; >> + >> +    /* Calculate the write size based on the write_end */ >> +    size = write_end - (index << PAGE_SHIFT); >> +    order = filemap_get_order(size); >> +    if (!order) >> +        return 0; >> + >> +    /* If we're not aligned, allocate a smaller folio */ >> +    if (index & ((1UL << order) - 1)) >> +        order = __ffs(index); >> + >> +    order = min_t(size_t, order, MAX_PAGECACHE_ORDER); >> +    return order > 0 ? BIT(order + 1) - 1 : 0; >> +} >> + >>   static unsigned int shmem_huge_global_enabled(struct inode *inode, >> pgoff_t index, >>                             loff_t write_end, bool shmem_huge_force, >> +                          struct vm_area_struct *vma, >>                             unsigned long vm_flags) >>   { >> +    unsigned long within_size_orders; >> +    unsigned int order; >> +    pgoff_t aligned_index; >>       loff_t i_size; >>       if (HPAGE_PMD_ORDER > MAX_PAGECACHE_ORDER) > > We can allow all orders up to MAX_PAGECACHE_ORDER, > shmem_mapping_size_orders() handles it properly. > > So maybe we should drop this condition and use instead below where we have > > return BIT(HPAGE_PMD_ORDER); > > instead something like. > > return HPAGE_PMD_ORDER > MAX_PAGECACHE_ORDER ? 0 : BIT(HPAGE_PMD_ORDER); > > Ideally, factoring it out somehow > > > int maybe_pmd_order = HPAGE_PMD_ORDER > MAX_PAGECACHE_ORDER ? 0 : > BIT(HPAGE_PMD_ORDER); > > ... > > return maybe_pmd_order; Good point. Will do. > >> @@ -564,15 +604,41 @@ static unsigned int >> shmem_huge_global_enabled(struct inode *inode, pgoff_t index >>       if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE) >>           return BIT(HPAGE_PMD_ORDER); > > Why not force-enable all orders (of course, respecting > MAX_PAGECACHE_ORDER and possibly VMA)? The ‘force’ option will affect the tmpfs mmap()'s huge allocation, which I intend to handle in a separate patch as we discussed. Additionally, for the huge page allocation of tmpfs mmap(), I am also considering the readahead approach for the pagecache. >> +    /* >> +     * The huge order allocation for anon shmem is controlled through >> +     * the mTHP interface, so we still use PMD-sized huge order to >> +     * check whether global control is enabled. >> +     * >> +     * For tmpfs mmap()'s huge order, we still use PMD-sized order to >> +     * allocate huge pages due to lack of a write size hint. >> +     * >> +     * Otherwise, tmpfs will allow getting a highest order hint based on >> +     * the size of write and fallocate paths, then will try each >> allowable >> +     * huge orders. >> +     */ >>       switch (SHMEM_SB(inode->i_sb)->huge) { >>       case SHMEM_HUGE_ALWAYS: >> -        return BIT(HPAGE_PMD_ORDER); >> -    case SHMEM_HUGE_WITHIN_SIZE: >> -        index = round_up(index + 1, HPAGE_PMD_NR); >> -        i_size = max(write_end, i_size_read(inode)); >> -        i_size = round_up(i_size, PAGE_SIZE); >> -        if (i_size >> PAGE_SHIFT >= index) >> +        if (vma) >>               return BIT(HPAGE_PMD_ORDER); >> + >> +        return shmem_mapping_size_orders(inode->i_mapping, index, >> write_end); >> +    case SHMEM_HUGE_WITHIN_SIZE: >> +        if (vma) >> +            within_size_orders = BIT(HPAGE_PMD_ORDER); >> +        else >> +            within_size_orders = >> shmem_mapping_size_orders(inode->i_mapping, >> +                                       index, write_end); >> + >> +        order = highest_order(within_size_orders); >> +        while (within_size_orders) { >> +            aligned_index = round_up(index + 1, 1 << order); >> +            i_size = max(write_end, i_size_read(inode)); >> +            i_size = round_up(i_size, PAGE_SIZE); >> +            if (i_size >> PAGE_SHIFT >= aligned_index) >> +                return within_size_orders; >> + >> +            order = next_order(&within_size_orders, order); >> +        } >>           fallthrough; >>       case SHMEM_HUGE_ADVISE: >>           if (vm_flags & VM_HUGEPAGE) > > I think the point here is that "write" -> no VMA -> vm_flags == 0 -> no > code changes needed :) Yes. Currently the fadvise() have no HUGEPAGE handling, so I will drop the 'fadvise' in the doc.