Re: [rfc][patch] remove racy sync_page?

Nick Piggin
2006-06-02T02:34:36Z

Linus Torvalds wrote:
>
> On Thu, 1 Jun 2006, Nick Piggin wrote:
>
>>If this wasn't clear: I don't mean per-task plugs as in "the task
>>explicitly plugs and unplugs the block device"[*]; I mean really
>>per-task plugs.
>
>
> That would be insane. It would mean that you'd have to unplug whether you

I don't think it is.

> wanted to or not. Ie you've now made "sys_readahead()" impossible to do
> well, and doing read-ahead across multiple files.

Now it is you who are ignoring what I've been saying. I've been saying
that I don't think your sys_readahead examples have had much to do with
plugging:

1. If there are no other requests to seek to, plugging doesn't matter;
2. If there are other requests to seek to, the queue won't be plugged
or will soon become unplugged anyway. So the current system isn't
somehow going to do the right thing every time and be immune to
seeking.

>
> You're ignoring all the _reasons_ for plugging in the first place.

I'm not, but the current system of plugging isn't ideal. Anyway, there
isn't any point going on about it, if I want to change anything I at
least need to come back with numbers.

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SUSE Labs, Novell Inc.
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