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Message-ID: <20180402060354epcms5p391e8f43648898d6d7dbd2ceb274f3cd9@epcms5p3> Date: Mon, 02 Apr 2018 11:33:54 +0530 From: Maninder Singh <maninder1.s@...sung.com> To: "sergey.senozhatsky.work@...il.com" <sergey.senozhatsky.work@...il.com> CC: "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>, "davem@...emloft.net" <davem@...emloft.net>, "minchan@...nel.org" <minchan@...nel.org>, "ngupta@...are.org" <ngupta@...are.org>, "keescook@...omium.org" <keescook@...omium.org>, "anton@...msg.org" <anton@...msg.org>, "ccross@...roid.com" <ccross@...roid.com>, "tony.luck@...el.com" <tony.luck@...el.com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "colin.king@...onical.com" <colin.king@...onical.com>, "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, PANKAJ MISHRA <pankaj.m@...sung.com>, AMIT SAHRAWAT <a.sahrawat@...sung.com>, Vaneet Narang <v.narang@...sung.com> Subject: Re: [PATCH 0/1] cover-letter/lz4: Implement lz4 with dynamic offset length. Hello, >> (Added cover letter to avoid much text in patch description) >> >> LZ4 specification defines 2 byte offset length for 64 KB data. >> But in case of ZRAM we compress data per page and in most of >> architecture PAGE_SIZE is 4KB. So we can decide offset length based >> on actual offset value. For this we can reserve 1 bit to decide offset >> length (1 byte or 2 byte). 2 byte required only if ofsset is greater than 127, >> else 1 byte is enough. > >So what happens if I compress the data on a system with no dyn >offset and then send it over the network to a machine which has >dyn offset? Or, say, I have a USB stick with a compression enabled >FS, store files on a dyn offset enabled PC and then mount that USB >stick on a machine with no dyn offset support. And vice versa. lz4_dyn is not an extension of LZ4 so there is no backward compatibility. Consider this as a different algorithm adapted from LZ4 for better compression ratio. Thanks Maninder Singh
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