From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 78E2D3AFD1F; Wed, 9 Sep 2026 21:02:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788987751; cv=none; b=Aa9/hR2J0IyPpVkQSWvRhJ1Mp2JyLM7tTxosCFEXA07RhxG1C9i/BFymnDGVpk6viENmJ2dRMIpTXWH7JyEWrz5SIckCRf8mTkxF0x4mUXhF/SJL1vk99Ft42vfxjYUoJaRF6Dp8u9mnFywqKw6A7+ixE0MqRXgz+rpIZ1Q/JOg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788987751; c=relaxed/simple; bh=XroBXL6pQL/1Yo+YMyUb6NtDEfey2fpxbNMt3JZ3j1Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=O27i3v3v0l39bGI//TAWAcGeqzY05ooNeygiG1dyhDAeZWROoLo0voJ8+qSELI5RjZHZigNpiN3oU6rusUdoKkPt1Dr3w3RDbbW4Sw/ko9kkGtFjflaeqWOEiKuKonIcNV8TNrZU2fJ9bolo2fMiBJehKszGfo1PegBnV+FNvl8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JsYAfxu1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JsYAfxu1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 789511F000FF; Wed, 9 Sep 2026 21:02:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788987750; bh=PbffVcQI+xFo5ygFA6oW/7Qdqg1wmtzoef67UMGLgVQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=JsYAfxu1gchV4emYg7c9RhVMIwWcOiYtQtWTqkhBqovirS1d/uM8eJhtCgV5mkD/B jtdUTfyMVT8JPIyYjU0PgQKT3kn1UEWfrK/t7D8v5T+wL4VVeP9LCUTjkQyo0iRuPW tJGJmJxjFa5s9bTzqCZxWc67j+EruBLxBXg24TMB/cJB9eKUXiQjWU6z5UwU6i/8Up ZsV/uTeK8KLQ7vftbOlBB1bVJLObXp4qt0MB1MWnwOqiShKhZslRW7RL/35/mXLhFF /7kKUA8EMixpQNc8Xbzhlaby4o3v55KOFjm9VkNEoiiyoXbMQBe4he6nGJqqdzxj5M bH0IH0Wbjd9hw== Message-ID: Date: Wed, 9 Sep 2026 23:02:20 +0200 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 06/26] mm/fbatch: fbatch_drain_lazyfree(onstack fbatch) before ptl unlock Content-Language: en-US To: Hugh Dickins , Andrew Morton Cc: Ackerley Tng , Alexander Viro , Alexandre Ghiti , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , Claudio Imbrenda , David Hildenbrand , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Kiryl Shutsemau , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Yang Shi , Yu Zhao , Zach O'Keefe , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <17e1a6c3-525b-1cc3-0731-349f0850e3ea@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/9/26 11:53, Hugh Dickins wrote: > Re-enable lazyfree batching for MADV_FREE. But it's not safe now to leave > potentially stale (then reused) folios in a per-cpu fbatch for lazyfree. > Instead, madvise_free_pte_range() keep an fbatch on its stack, and drain > it each time before dropping pagetable lock, while the folios are secure. > > Ignore folio_may_be_lru_cached() and lru_cache_disabled(): limitations > irrelevant to this fbatch drained under spinlock (even if RT); though > in practice madvise_free_huge_pmd() does have to drain every time. > > Signed-off-by: Hugh Dickins It seems correct to me, so: Reviewed-by: Vlastimil Babka (SUSE) Might be that something regresses performance though. Guess we'll see. Also seems to me that if this patch was preparatory, the batching wouldn't have to be temporarily disabled. Doesn't matter ultimately though.