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Sun, 5 Apr 2020 06:57:56 -0400 Received: by zaphod.cobb.me.uk (Postfix, from userid 107) id 009859C3E1; Sun, 5 Apr 2020 11:57:54 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cobb.uk.net; s=201703; t=1586084275; bh=GZcnd+ahhl/Z2Urgft1wWdQQrho4zf74/N2VGHS6dZU=; h=Subject:To:References:From:Date:In-Reply-To:From; b=NTH5lqnWpTyAmTyrVWJWrhzQdkDGlzWh5R1Ef35bWMVVeR7tjvlNHL46ADx4yfy3V NIBL/cK7Hf6rRJtPhrWEnG0++kK+2pZKyAuT38uPjahP7AQ/DQ6b71jfxEM217dwbR K4ccwEZrqgXWCFsT3zyCmQkOJGKJmblrBi7JAjXW6llSF6tttGeY8LMOVXIWr+anNi fTBqOnzwKnEOdki3tpEh5wf5aLnbiC41aWcTdecwpuzGHtMF/ayS3Cg8W6va6c0cV/ qcKKC2pJd1DGdslTN5PtHdxOHhxYuzK0rwnUnxaDJ5nJEFSiQf8iTyYHjoGUCwZ3wr zr+1A+R2cx3EQ== Received: from black.home.cobb.me.uk (unknown [192.168.0.205]) by zaphod.cobb.me.uk (Postfix) with ESMTP id 2BE6D9B9B1; Sun, 5 Apr 2020 11:57:51 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cobb.uk.net; s=201703; t=1586084271; bh=GZcnd+ahhl/Z2Urgft1wWdQQrho4zf74/N2VGHS6dZU=; h=Subject:To:References:From:Date:In-Reply-To:From; b=jho7+McTu97jbWRQOcPjjUBbXHThV/mKuwHfUHYO8+My52dEG3Rk/g934oOEXyiaQ wySzfLgTsjdYaFjUy9jRIXlJGvtvcSzFpK7XzjB1t+l3kwcf0W0xJvse/WrOuPRUmq GVgkI9YB0Rg6JgjXA+/vrFK0i8a1qHsRwDGybmjVVEh2PzepFp0R4VcjiqsIb2csok dB4iEcuuzSqTkp2x7NsQCK6Pt4yZTt6YsakkTU9j35Y9xFh5wiSZ+/O3B60taxBDm8 8VkLmz/7vqhzWxcrp2riyaJ84Wpvus09cu6hPN0rdztd0jygJdq/RCexWIitqgVfRo 5vM0MWi9YR2Zg== Received: from [192.168.0.211] (novatech.home.cobb.me.uk [192.168.0.211]) by black.home.cobb.me.uk (Postfix) with ESMTPS id EBD2CE0503; Sun, 5 Apr 2020 11:57:49 +0100 (BST) Subject: Re: [RFC][PATCH V3] btrfs: ssd_metadata: storing metadata on SSD To: Goffredo Baroncelli , linux-btrfs@vger.kernel.org References: <20200405082636.18016-1-kreijack@libero.it> From: Graham Cobb Openpgp: preference=signencrypt Autocrypt: addr=g.btrfs@cobb.uk.net; prefer-encrypt=mutual; keydata= mQINBFaetnIBEAC5cHHbXztbmZhxDof6rYh/Dd5otxJXZ1p7cjE2GN9hCH7gQDOq5EJNqF9c VtD9rIywYT1i3qpHWyWo0BIwkWvr1TyFd3CioBe7qfo/8QoeA9nnXVZL2gcorI85a2GVRepb kbE22X059P1Z1Cy7c29dc8uDEzAucCILyfrNdZ/9jOTDN9wyyHo4GgPnf9lW3bKqF+t//TSh SOOis2+xt60y2In/ls29tD3G2ANcyoKF98JYsTypKJJiX07rK3yKTQbfqvKlc1CPWOuXE2x8 DdI3wiWlKKeOswdA2JFHJnkRjfrX9AKQm9Nk5JcX47rLxnWMEwlBJbu5NKIW5CUs/5UYqs5s 0c6UZ3lVwinFVDPC/RO8ixVwDBa+HspoSDz1nJyaRvTv6FBQeiMISeF/iRKnjSJGlx3AzyET ZP8bbLnSOiUbXP8q69i2epnhuap7jCcO38HA6qr+GSc7rpl042mZw2k0bojfv6o0DBsS/AWC DPFExfDI63On6lUKgf6E9vD3hvr+y7FfWdYWxauonYI8/i86KdWB8yaYMTNWM/+FAKfbKRCP dMOMnw7bTbUJMxN51GknnutQlB3aDTz4ze/OUAsAOvXEdlDYAj6JqFNdZW3k9v/QuQifTslR JkqVal4+I1SUxj8OJwQWOv/cAjCKJLr5g6UfUIH6rKVAWjEx+wARAQABtDNHcmFoYW0gQ29i YiAoUGVyc29uYWwgYWRkcmVzcykgPGdyYWhhbUBjb2JiLnVrLm5ldD6JAlEEEwECADsCGwEG CwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAhkBBQJWnr9UFRhoa3A6Ly9rZXlzLmdudXBnLm5l dAAKCRBv35GGXfm3Tte8D/45+/dnVdvzPsKgnrdoXpmvhImGaSctn9bhAKvng7EkrQjgV3cf C9GMgK0vEJu+4f/sqWA7hPKUq/jW5vRETcvqEp7v7z+56kqq5LUQE5+slsEb/A4lMP4ppwd+ TPwwDrtVlKNqbKJOM0kPkpj7GRy3xeOYh9D7DtFj2vlmaAy6XvKav/UUU4PoUdeCRyZCRfl0 Wi8pQBh0ngQWfW/VqI7VsG3Qov5Xt7cTzLuP/PhvzM2c5ltZzEzvz7S/jbB1+pnV9P7WLMYd EjhCYzJweCgXyQHCaAWGiHvBOpmxjbHXwX/6xTOJA5CGecDeIDjiK3le7ubFwQAfCgnmnzEj pDG+3wq7co7SbtGLVM3hBsYs27M04Oi2aIDUN1RSb0vsB6c07ECT52cggIZSOCvntl6n+uMl p0WDrl1i0mJUbztQtDzGxM7nw+4pJPV4iX1jJYbWutBwvC+7F1n2F6Niu/Y3ew9a3ixV2+T6 aHWkw7/VQvXGnLHfcFbIbzNoAvI6RNnuEqoCnZHxplEr7LuxLR41Z/XAuCkvK41N/SOI9zzT GLgUyQVOksdbPaxTgBfah9QlC9eXOKYdw826rGXQsvG7h67nqi67bp1I5dMgbM/+2quY9xk0 hkWSBKFP7bXYu4kjXZUaYsoRFEfL0gB53eF21777/rR87dEhptCnaoXeqbkBDQRWnrnDAQgA 0fRG36Ul3Y+iFs82JPBHDpFJjS/wDK+1j7WIoy0nYAiciAtfpXB6hV+fWurdjmXM4Jr8x73S xHzmf9yhZSTn3nc5GaK/jjwy3eUdoXu9jQnBIIY68VbgGaPdtD600QtfWt2zf2JC+3CMIwQ2 fK6joG43sM1nXiaBBHrr0IadSlas1zbinfMGVYAd3efUxlIUPpUK+B1JA12ZCD2PCTdTmVDe DPEsYZKuwC8KJt60MjK9zITqKsf21StwFe9Ak1lqX2DmJI4F12FQvS/E3UGdrAFAj+3HGibR yfzoT+w9UN2tHm/txFlPuhGU/LosXYCxisgNnF/R4zqkTC1/ao7/PQARAQABiQIlBBgBAgAP BQJWnrnDAhsMBQkJZgGAAAoJEG/fkYZd+bdO9b4P/0y3ADmZkbtme4+Bdp68uisDzfI4c/qo XSLTxY122QRVNXxn51yRRTzykHtv7/Zd/dUD5zvwj2xXBt9wk4V060wtqh3lD6DE5mQkCVar eAfHoygGMG+/mJDUIZD56m5aXN5Xiq77SwTeqJnzc/lYAyZXnTAWfAecVSdLQcKH21p/0AxW GU9+IpIjt8XUEGThPNsCOcdemC5u0I1ZeVRXAysBj2ymH0L3EW9B6a0airCmJ3Yctm0maqy+ 2MQ0Q6Jw8DWXbwynmnmzLlLEaN8wwAPo5cb3vcNM3BTcWMaEUHRlg82VR2O+RYpbXAuPOkNo 6K8mxta3BoZt3zYGwtqc/cpVIHpky+e38/5yEXxzBNn8Rn1xD6pHszYylRP4PfolcgMgi0Ny 72g40029WqQ6B7bogswoiJ0h3XTX7ipMtuVIVlf+K7r6ca/pX2R9B/fWNSFqaP4v0qBpyJdJ LO/FP87yHpEDbbKQKW6Guf6/TKJ7iaG3DDpE7CNCNLfFG/skhrh5Ut4zrG9SjA+0oDkfZ4dI B8+QpH3mP9PxkydnxGiGQxvLxI5Q+vQa+1qA5TcCM9SlVLVGelR2+Wj2In+t2GgigTV3PJS4 tMlN++mrgpjfq4DMYv1AzIBi6/bSR6QGKPYYOOjbk+8Sfao0fmjQeOhj1tAHZuI4hoQbowR+ myxb Message-ID: <58e315a1-0307-9a26-8fb4-fd5220c1d5a6@cobb.uk.net> Date: Sun, 5 Apr 2020 11:57:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200405082636.18016-1-kreijack@libero.it> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 05/04/2020 09:26, Goffredo Baroncelli wrote: ... > I considered the following scenarios: > - btrfs over ssd > - btrfs over ssd + hdd with my patch enabled > - btrfs over bcache over hdd+ssd > - btrfs over hdd (very, very slow....) > - ext4 over ssd > - ext4 over hdd > > The test machine was an "AMD A6-6400K" with 4GB of ram, where 3GB was used > as cache/buff. > > Data analysis: > > Of course btrfs is slower than ext4 when a lot of sync/flush are involved. Using > apt on a rotational was a dramatic experience. And IMHO this should be replaced > by using the btrfs snapshot capabilities. But this is another (not easy) story. > > Unsurprising bcache performs better than my patch. But this is an expected > result because it can cache also the data chunk (the read can goes directly to > the ssd). bcache perform about +60% slower when there are a lot of sync/flush > and only +20% in the other case. > > Regarding the test with force-unsafe-io (fewer sync/flush), my patch reduce the > time from +256% to +113% than the hdd-only . Which I consider a good > results considering how small is the patch. > > > Raw data: > The data below is the "real" time (as return by the time command) consumed by > apt > > > Test description real (mmm:ss) Delta % > -------------------- ------------- ------- > btrfs hdd w/sync 142:38 +533% > btrfs ssd+hdd w/sync 81:04 +260% > ext4 hdd w/sync 52:39 +134% > btrfs bcache w/sync 35:59 +60% > btrfs ssd w/sync 22:31 reference > ext4 ssd w/sync 12:19 -45% Interesting data but it seems to be missing the case of btrfs ssd+hdd w/sync without your patch in order to tell what difference your patch made. Or am I confused?