Messages in this thread | | | Date | Mon, 23 Jan 2006 11:50:41 -0800 | From | Nate Diller <> | Subject | Re: [PATCH 1/2][RESEND] Default iosched fixes (was: Fall back io scheduler for 2.6.15?) |
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On 1/21/06, Jens Axboe <axboe@suse.de> wrote: > On Fri, Jan 20 2006, Nate Diller wrote: > > My previous default iosched patch did a poor job dealing with the > > 'elevator=' boot-time option. The old behavior falls back to the > > compiled-in default if the requested one is not registered at boot > > time. This patch dynamically evaluates which default > > to use, and emits a suitable error message when the requested scheduler > > is not available. It also does the 'as' -> 'anticipatory' conversion > > before elevator registration, which along with a modified registration > > function, allows it to correctly indicate which default scheduler is > > in use. > > I'm a little confused by your description - what problem does this patch > actually solve? We already fall back to the default, and we already do > the "as" conversion. It does seem to cleanup the code, just curious > since your description seems to promise a little more than what it > actually adds.
It makes the ' (default)' printk that happens at elevator registration time behave (more) correctly. My original patch rather ignored that segment of code. The current behavior is to only print ' (default)' when one was specified at boot time, and not if 'as' was requested either, since it doesn't understand the 'as -> anticipatory' conversion. Now, it will display correctly the one selected at compile-time, if none was specified at boot, and when the boot-time option was 'as'.
It also handles modular defaults better; although they cannot be specified in kconfig, a default requested at boot-time will now still work, even if it's a module. When the boot-time requested scheduler is not loaded, it will fall back to the compiled-in default; when it is, it gets used.
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