From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from omr1.cc.ipv6.vt.edu ([2607:b400:92:8300:0:c6:2117:b0e] helo=omr1.cc.vt.edu) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1gJi8c-0002cM-4B for kernelnewbies@kernelnewbies.org; Mon, 05 Nov 2018 11:54:06 -0500 Received: from mr4.cc.vt.edu (junk.cc.ipv6.vt.edu [IPv6:2607:b400:92:9:0:9d:8fcb:4116]) by omr1.cc.vt.edu (8.14.4/8.14.4) with ESMTP id wA5Gs542001197 for ; Mon, 5 Nov 2018 11:54:05 -0500 Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by mr4.cc.vt.edu (8.14.7/8.14.7) with ESMTP id wA5GrxIi015400 for ; Mon, 5 Nov 2018 11:54:05 -0500 Received: by mail-qk1-f198.google.com with SMTP id l7-v6so22778380qkd.5 for ; Mon, 05 Nov 2018 08:54:05 -0800 (PST) From: valdis.kletnieks@vt.edu To: "Austin S. Hemmelgarn" Subject: Re: Creating compressed backing_store as swapfile In-Reply-To: <6a1f57b6-503c-48a2-689b-3c321cd6d29f@gmail.com> References: <20181105155815.i654i5ctmfpqhggj@angband.pl> <79d0c96a-a0a2-63ec-db91-42fd349d50c1@gmail.com> <42594.1541434463@turing-police.cc.vt.edu> <6a1f57b6-503c-48a2-689b-3c321cd6d29f@gmail.com> Mime-Version: 1.0 Date: Mon, 05 Nov 2018 11:53:56 -0500 Message-ID: <83467.1541436836@turing-police.cc.vt.edu> Cc: Adam Borowski , kernelnewbies@kernelnewbies.org, Pintu Agarwal , open list , linux-mm@kvack.org List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============5597532758907170989==" Errors-To: kernelnewbies-bounces@kernelnewbies.org Message-ID: <20181105165356.EnuqeyWOpNKfqLr6AfFiRm20LYndvGGV6rr1Q5CIHX8@z> --===============5597532758907170989== Content-Type: multipart/signed; boundary="==_Exmh_1541436836_4003P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit --==_Exmh_1541436836_4003P Content-Type: text/plain; charset=us-ascii On Mon, 05 Nov 2018 11:28:49 -0500, "Austin S. Hemmelgarn" said: > Also, it's probably worth noting that BTRFS doesn't need to decompress > the entire file to read or write blocks in the middle, it splits the > file into 128k blocks and compresses each of those independent of the > others, so it can just decompress the 128k block that holds the actual > block that's needed. Presumably it does something sane with block allocation for the now-compressed 128K that's presumably much smaller. Also, that limits the damage from writing to the middle of a compression unit.... That *does* however increase the memory requirement - you can OOM or deadlock if your read/write from the swap needs an additional 128K for the compression buffer at an inconvenient time... --==_Exmh_1541436836_4003P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.8.0 04/21/2017 iQEVAwUBW+B1pI0DS38y7CIcAQIaSwgAlaWBTJLuKtJT7ru/WLIqVahEPpFO8vgl 0Wd9hwwQSj1a4HtpAkeRTo3/24JBDnIg315A8Q+YW0/zF9MP2cecGTCDT4tmJUR1 NhN2hoAnKvLleU5ZebPygptkEkiQdbs7G92ok/Zi32lPUwWVt1ZdQG3HVYHWtNxJ ret95nyOWAgBJFJmb+I9kiO8O3RewbnfPjLRiUA1d1iaaK6Zilur44fG6K5KN5Yv jxN/ee4UM+w/u3cTEpVyAdFqAVq8phDKn1Pa53LSa6TtHXoUOI3ir/k2owUxfzE6 pO+Len2d4Y2U1VcrfyB5yaLyd5gFGoe82qwsgregzqCbaygKQ4UgPg== =OHwC -----END PGP SIGNATURE----- --==_Exmh_1541436836_4003P-- --===============5597532758907170989== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies --===============5597532758907170989==--