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Date: Mon, 5 Mar 2007 12:49:45 +0100 From: Jörn Engel <joern@...ybastard.org> To: Anton Altaparmakov <aia21@....ac.uk> Cc: Ulrich Drepper <drepper@...hat.com>, Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@...radead.org>, Dave Kleikamp <shaggy@...ux.vnet.ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, "Amit K. Arora" <aarora@...ux.vnet.ibm.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, suparna@...ibm.com, cmm@...ibm.com, alex@...sterfs.com, suzuki@...ibm.com Subject: Re: [RFC] Heads up on sys_fallocate() On Mon, 5 March 2007 00:32:14 +0000, Anton Altaparmakov wrote: > > I don't know how your compression algorithm works [...] LogFS is designed for flash media, so it does not have to worry much about reducing disk seeks. It is log-structured, which simplifies compression further. When writing a block, it basically compresses it and appends it to the log. Writes only have to be byte-aligned, so no space is lost for padding. The bad news for posix_fallocate() is that even if libc is smart enough to write random data, mmap() can still cause problems. If the VM decides to write a given page twice, the second write compresses better and the medium has filled up between the two writes, the users will have fun. Jörn -- Joern's library part 9: http://www.scl.ameslab.gov/Publications/Gus/TwelveWays.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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