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Re: e2fslibs for ext2fs?

From: Ognyan Kulev
Subject: Re: e2fslibs for ext2fs?
Date: Sat, 16 Aug 2003 11:32:44 +0300
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030714 Debian/1.4-2

Marcus Brinkmann wrote:
Note that I mentioned io_map and that its implementation will not be helped
at all by such a simple library.  That includes large file support.  Large
filesystems might trivially be supported by such a library if it always
accesses the store directly, without any mapping.  No mapping however means
no cache, and that's where your performance is saying good bye.

In addition, all these library functions are layered upon a block layer inefficiently. The block layer has a very small cache (8 blocks). You can increase block count, but the cache algorithm is optimized for small cache and will definately be very inefficient for larger caches. The library functions that need to use part of a block don't get pointer to the already cached block, but supply own buffer where the block layer will copy bytes from its cache. This means that there are _a lot_ of redundant memory copies.

This doesn't mean the library is bad. It's just optimized for e2fsck and other offline programs, like e2tools.

Ognyan Kulev <ogi@{fmi.uni-sofia.bg,fsa-bg.org}>
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