4 ms·
AFAIK, ureadahead just keeps track of which files/blocks are touched during bootup/startx and pre-reads them into a cache at the very beginning of the boot sequ
by yason 15y ago
AFAIK, ureadahead just keeps track of which files/blocks are touched during bootup/startx and pre-reads them into a cache at the very beginning of the boot sequence so you will effectively boot from cache.
This still requires seeking to several semi-random areas of the disk while prereading which e4rat is fixing by physically moving the needed blocks adjacent to eachother.
- deleted 15y ago[deleted]
- sciurus 15y agoFor some reason, I had the idea that ureadahead's pack files actually contained the contents of the blocks that needed to be read during boot, turning readahead into a sequential operation. After reading the manpage today, I see that I was mistaken.
- ntoshev 15y agoIt would be nice if someone installed e4rat on Ubuntu (with ureadahead) and reported the performance.
- obtu 15y agoSince ureadahead looks at blocks and not files, it has a potential speed advantage if the boot process is opening some large files but not reading them in full. Edit: except the ureadahead packfile only points to the blocks and files, it does not provide a way to inline them. So e4rat is almost certainly faster. It's a shame it is ext4 specific. Apparently Scott James Remnant, the ureadahead developer, considered feeding the collected info to a defragmenter: http://ubuntuforums.org/showthread.php?t=1434502 http://ubuntuforums.org/showthread.php?t=1434502 ; this would be nice, as it means a single package is responsible for the feature, and filesystems perform to the best of their ability whether or not they have ext4-like fine-grained control of defragmentation.
- rcthompson 15y agoSo it sounds like the filesystem-reorganizing features of e4eat (but not the profiling features) would be complementary to ureadahead.