Improve so it works on HDD disks

Testing has shown that due to the better pack generation, sreadhead is actually just as good as readahead-list *without* being optimised - HDD optimisation is still desirable though to get even more performance out of it

I cannot confirm your observation. I've 'bootcharted' two systems and with both sreadahead was slower than not using preloading at all - readahead-list was faster [I've stopped before GDM loading for pack file generation and used that list with readahead].

Sys 1 (AMD Opteron 144 @ 2.65GHz, 2GB RAM, 7200rpm disk):
- pack file: 733 files with 73.456.165 bytes
* no (s)readahead: 18.0s
* readahead: 17.4s
* sreadahead: 18.4s
* sreadahead started with --no-fork: 19.3s

Sys 2 (Intel Core Duo T2400 @ 1.83GHz, 2GB RAM, 5400rpm disk):
- pack file: 829 files with 57.408.165 bytes
* no (s)readahead: 23.1s
* readahead: 21.9s
* sreadahead: 24.6s
* sreadahead started with --no-fork: 24.3s

The gap is not big but it's there.

---

2.6.31-9-generic (Core Duo system used -7-generic)

readahead:
  Installed: 1:0.20050517.0220-1ubuntu5

sreadahead:
  Installed: 1.0-2

After you installed sreadahead, did you reboot twice and measure the second
time? I believe sreadahead needs to profile the boot the first time around.

On 09/01/2009 11:22 AM, Hernando Torque wrote:
> I cannot confirm your observation. I've 'bootcharted' two systems and
> with both sreadahead was slower than not using preloading at all -
> readahead-list was faster [I've stopped before GDM loading for pack file
> generation and used that list with readahead].
>
> Sys 1 (AMD Opteron 144 @ 2.65GHz, 2GB RAM, 7200rpm disk):
> - pack file: 733 files with 73.456.165 bytes
> * no (s)readahead: 18.0s
> * readahead: 17.4s
> * sreadahead: 18.4s
> * sreadahead started with --no-fork: 19.3s
>
> Sys 2 (Intel Core Duo T2400 @ 1.83GHz, 2GB RAM, 5400rpm disk):
> - pack file: 829 files with 57.408.165 bytes
> * no (s)readahead: 23.1s
> * readahead: 21.9s
> * sreadahead: 24.6s
> * sreadahead started with --no-fork: 24.3s
>
> The gap is not big but it's there.
>
> ---
>
> 2.6.31-9-generic (Core Duo system used -7-generic)
>
> readahead:
> Installed: 1:0.20050517.0220-1ubuntu5
>
> sreadahead:
> Installed: 1.0-2
>

Yes. First boot was to a login prompt w/o GDM loading (so the pack file would only contain GRUB -> GDM files). Then I went to /var/lib/sreadahead and waited for the pack file to show up. Next boot I ran with bootchart enabled.

I repeated the test with the AMD system but this time took bootcharts of a full boot to desktop:

- pack file: 1531 files with 79.994.830 bytes
* readahead: 37s
* sreadahead --no-fork: 41s

Just for the record: I'm extracting the file list for readahead from the pack file, I'm not just using the pack file with readahead. So those file lists should be the same.

That's not a fair test.

Please compare readahead-list for your system with the file list that *readahead* generated, against sreadahead for your system with the file list that *sreadahead* generated.

Part of the reason for switching is that sreadahead generates better pack file lists, such that sreadahead results in a generally as fast or faster boot than readahead-list, even though sreadahead isn't optimised for HDD yet.

Ok, this time with untouched file lists (again on the AMD system).

readahead: 36s
- /etc/readahead/boot: 2399 files with 204.983.516 bytes (stopped readahead's profiling after the desktop was loaded)

sreadahead --no-fork: 42s
- /var/lib/sreadahead/pack: 1530 files with 81.780.819 bytes

On Wed, 2009-09-02 at 21:53 +0000, Hernando Torque wrote:

> readahead: 36s
> - /etc/readahead/boot: 2399 files with 204.983.516 bytes (stopped readahead's profiling after the desktop was loaded)
>
Again, please stop screwing around with the readahead lists.

If you're not going to compare the readahead package *as it is shipped
with Ubuntu* against the sreadahead package *as it is shipped with
Ubuntu*, you're not helping.

 status invalid

Scott
--
Scott James Remnant
<email address hidden>

> If you're not going to compare the readahead package *as it is shipped
> with Ubuntu* against the sreadahead package *as it is shipped with
> Ubuntu*, you're not helping.

I'm sorry, but that's not what you've asked for in #8. :-)

Using the 'boot' and 'desktop' file shipped with readahead I indeed get equal times for readahead, sreadahead and sreadahead --no-fork (usable desktop after ~24s on the Core Duo system with a 7200rpm disk).

Please note that I didn't want to make sreadahead look bad, I just couldn't confirm your observation. Thanks for clearing things up!