From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.gmx.net (mout.gmx.net [212.227.17.20]) (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 99E186FBC for ; Fri, 22 Dec 2023 06:14:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmx.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b="TYIYNkYY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.com; s=s31663417; t=1703225611; x=1703830411; i=quwenruo.btrfs@gmx.com; bh=JIXlgCn1JxDVlyaeD+tXujSldr0DyR00ylz5u7ZzWrM=; h=X-UI-Sender-Class:Date:Subject:To:References:From:In-Reply-To; b=TYIYNkYYHP9fQQ6ltbjd7HlcV6ShqtX6UCPBKL3no5pHPI6Tt1qFPNNNL1kv+Bve 8xqczkM8tKfvqVhfkxdA97COUVSlHDBGCZ3AoPCuZhfhV78iEgaMioT8m/YOh4TNm YgaSIvi9jGmA8AEB20b/ShK+82tw9B4tFy6dSO7u8C20cHzSIC0ggPBY4+ZQKW7Yz Z2mA3p0t8X/DxnH9Dk8ct7P8PHEzYAig8Rj1SNX4MGZgcHJyqnHgisfMAVMm2ovd7 0CCZf9Hwx2gH5qa+bubC/BULFIKFMlaDGHSG00kfg7cKHPrKRMvu5Fyp6aa9zyCsJ rSEflILnz8//CTu3Ng== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [172.16.0.153] ([193.115.114.154]) by mail.gmx.net (mrgmx105 [212.227.17.174]) with ESMTPSA (Nemesis) id 1Mk0NU-1qsSNm2uim-00kMdN; Fri, 22 Dec 2023 07:13:31 +0100 Message-ID: Date: Fri, 22 Dec 2023 16:43:27 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: BTRFS doesn't compress on the fly Content-Language: en-US To: Gerhard Wiesinger , linux-btrfs@vger.kernel.org References: <6ae85272-3967-417e-bc9a-e2141a4c688a@gmx.com> <6c2424bb-9c91-4ac0-970b-613ca97b3e01@gmx.com> <771df9a9-c7c3-40a7-a426-0126118d3af0@wiesinger.com> <9f4ad251-7af7-4f02-b388-64dd6c8257ac@gmx.com> <0c644c25-7ec4-43da-a70b-1632e87490b3@wiesinger.com> From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: <0c644c25-7ec4-43da-a70b-1632e87490b3@wiesinger.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:29LoQ465Su+lriLIoiDjondSCFHn4qr6iyQIjN5egQR1YHYfAVE fxXdJxdyGyBx6jyO56GlhXc2dOoNDGAgMDsqkHlEwp8FCMzRC85FzgSwv7HuSAeIv7QFpyc 379DeELDIKLYSJ0mScRkvHdEy5d+PXol7yCXFTaJwnnFyHKdDlacQSppZwFPwAGxcOvNA9t QnftQkT8YaYEaZJBH0cVA== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:S/wk++4cczM=;xx8yRiczSlFH7NYto9g3xoMV31K gcw/GYLLeofpd3lYsTIO0r+Ab0irM2fzs16aog66p983gb6c2rHtSU7zDfPEdFEnAkWtnXz+T 8XlMlJWCJ5MgI/wqgmKHcfMMuBifzk6zjEYHhertEb/6utDDCJ/QZHj8KFZ5oZh4PPrNoBSQB qT7MNePusp3zXdw97Wx5QRUfGxKIYaNsEDwXXB/I3urX7kE9JmybB8oIoNiP8lEpYbJxQpCfm e2r2AubYOCzDonyY8rDkpI8R1vt6UhekNMZDPhihcd7h5bBcDVqjD/UCthin0B9p1etN6ldNU Iez2wKQtkBie41agyZxfmZOhWH2cvh/I3wwl8d0WpAHa/l2B+7UtNCJ4EsNLe1sbMnc901WCi BTy1t7wMuw2UJcSSNzw6l6q98VzI8oa9feZx7KqMtf9BAmwA4ree5ssw+QoghWqhDSJJdra84 Pt+d+asbVb0YXfmq8gpn9xVlSg1HNS4qmFc6iq/lqPvw496eXhyrjTTvwtFwSRCknY3mp3QZ8 KpCfCmtj47ERwNmeBs7IY0oGxWElijeirnUgpMFAgs8zF3MsHCMdlatrOrzI9keMKhR039ZsY P/xt8FBe4X36M/nnFNxhxxHbqg8rrU6lVJ7cWzORtASW5//nVmLUMCeQRh9nFWJVtMCVYXpaT +pdCpnMNFpS4fxaQdiN99c9WbWMhxPTSXZ32ww99+UHlNCHOYGI4h3fnZMlpLVkDIYBDqACBe P4mGpX0B3xQETLs5bpHLszSQgi0SVKCwGgho2hC1jkvj29LjuffBKFFFQREkoCFgzqMXkvLox WuRnzLNBsGuyMo/x07dqaW0sRO7bWrTTr3+YQ+MmPtcX0p/Jkd9Waf67/ThScWpwmlmaO0pHm 4F1ckKaCMTlCTPkv0t2kpThxOQEpwpXGT1n/z4b/80ktGHk8wvCgGTq5PB7R+XwnjCQia8lNL sNnifEz5xnIQ3+CzJreJ3BTLQss= On 2023/12/22 16:28, Gerhard Wiesinger wrote: > On 03.12.2023 11:19, Qu Wenruo wrote: >> >> >>> BTW: >>> >>> if compression is forced, should be then just any "block" be compresse= d? >> >> There is a long existing problem with compression with preallocation. >> >> One easy example is, if we go compression for the preallocated range, >> what we do with the gap (compressed size is always smaller than the rea= l >> size). >> >> If we leave the gap, then the read performance can be even worse, as no= w >> we have to read several small extents with gaps between them, vs a larg= e >> contig read. >> >> IIRC years ago when I was a btrfs newbie, that's the direction I tried >> to go, but never reached upstream. >> >> Thus you can see some of the reason why we do not go compression for >> preallocated range. >> >> But I still don't believe we should go as the current behavior. >> We should still try to go compression as long as we know the write stil= l >> needs COW, thus we should fix it. > > > Any progress with the fix? Tried several solution, the best one would still lead to reserved space underflow. The proper fix would introduce some larger changes to the whole delalloc mechanism. Thus it's not something can be easily fixed yet. Thanks, Qu > > Thnx. > > Ciao, > > Gerhard >