From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-xd31.google.com ([2607:f8b0:4864:20::d31]) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.91) (envelope-from ) id 1gJhQl-0001OQ-4l for kernelnewbies@kernelnewbies.org; Mon, 05 Nov 2018 11:08:47 -0500 Received: by mail-io1-xd31.google.com with SMTP id p83-v6so6846864iod.12 for ; Mon, 05 Nov 2018 08:08:45 -0800 (PST) Subject: Re: Creating compressed backing_store as swapfile To: Adam Borowski , Pintu Agarwal References: <20181105155815.i654i5ctmfpqhggj@angband.pl> From: "Austin S. Hemmelgarn" Message-ID: <79d0c96a-a0a2-63ec-db91-42fd349d50c1@gmail.com> Date: Mon, 5 Nov 2018 11:07:12 -0500 MIME-Version: 1.0 In-Reply-To: <20181105155815.i654i5ctmfpqhggj@angband.pl> Content-Language: en-US Cc: linux-mm@kvack.org, open list , kernelnewbies@kernelnewbies.org List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kernelnewbies-bounces@kernelnewbies.org Message-ID: <20181105160712.fTt_JKZId18um_FmrfGQNq5BvrcXCDq5aZ1clZonNhQ@z> On 11/5/2018 10:58 AM, Adam Borowski wrote: > On Mon, Nov 05, 2018 at 08:31:46PM +0530, Pintu Agarwal wrote: >> Hi, >> >> I have one requirement: >> I wanted to have a swapfile (64MB to 256MB) on my system. >> But I wanted the data to be compressed and stored on the disk in my swapfile. >> [Similar to zram, but compressed data should be moved to disk, instead of RAM]. >> >> Note: I wanted to optimize RAM space, so performance is not important >> right now for our requirement. >> >> So, what are the options available, to perform this in 4.x kernel version. >> My Kernel: 4.9.x >> Board: any - (arm64 mostly). >> >> As I know, following are the choices: >> 1) ZRAM: But it compresses and store data in RAM itself >> 2) frontswap + zswap : Didn't explore much on this, not sure if this >> is helpful for our case. >> 3) Manually creating swapfile: but how to compress it ? >> 4) Any other options ? > > Loop device on any filesystem that can compress (such as btrfs)? The > performance would suck, though -- besides the indirection of loop, btrfs > compresses in blocks of 128KB while swap wants 4KB writes. Other similar > option is qemu-nbd -- it can use compressed disk images and expose them to a > (local) nbd client. Swap on any type of a networked storage device (NBD, iSCSI, ATAoE, etc) served from the local system is _really_ risky. The moment the local server process for the storage device gets forced out to swap, you deadlock. Performance isn't _too_ bad for the BTRFS case though (I've actually tested this before), just make sure you disable direct I/O mode on the loop device, otherwise you run the risk of data corruption. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies