linux-kernel - Re: "fb-defio: fix page list with concurrent processes"

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Message-ID: <87hcbsmmq0.fsf@pike.pond.sub.org>
Date:	Tue, 17 Jun 2008 11:31:35 +0200
From:	Markus Armbruster <armbru@...hat.com>
To:	"Jaya Kumar" <jayakumar.lkml@...il.com>
Cc:	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: "fb-defio: fix page list with concurrent processes"

"Jaya Kumar" <jayakumar.lkml@...il.com> writes:

> On Tue, Jun 17, 2008 at 12:34 AM, Markus Armbruster <armbru@...hat.com> wrote:
>> "Jaya Kumar" <jayakumar.lkml@...il.com> writes:
>>
>>> On Mon, Jun 16, 2008 at 3:05 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>>>> Your patch "fb-defio: fix page list with concurrent processes" definitely
>>>> seems to help with the suspend/resume problem I had with the Xen pvfb
>>>> device.  Is it queued up anywhere?  It seems to be a real bugfix, and should
>>>> probably be queued for 2.6.26...
>>>
>>> It isn't currently queued. I had intended to improve its performance
>>> by taking advantage of Andrew's suggestion of using !list_empty on the
>>> page->lru to avoid walking the page list to find the duplicate page,
>>> but I ran into trouble since the page starts off being on the lru
>>> list. I'll try to take a look at doing this next weekend.
>>>
>>> Thanks,
>>> jaya
>>
>> Well, we got a bug that makes the code useless in practice for us, and
>> a fix for it that's not quite as fast as it could be.  Which is
>> better, somewhat slow code, or somewhat useless code?  I'd like to see
>> the fix merged as soon as possible.  You can always improve its
>> performance later.
>>
>
> Ok, I didn't realize there was any time pressure. Keep in mind, I'm
> just a person doing this stuff for fun on weekends not someone under
> commercial pressures. Yup, I've got no problem if the old patch is
> requeued and merged.
>
> Thanks,
> jaya

Hey, it's your own fault!  If you wrote useless code in your spare
time, we wouldn't bother you ;->

Seriously, I appreciate your contributions, and I didn't mean to
pressure you.  Just to explain why I think it makes sense to merge
your fix now, and performance improvements later.
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