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Subject: RE: [PATCH 1/1] indirect function calls elimination in IO scheduler
Date: Thu, 1 Dec 2005 20:18:52 +0300
Message-ID: <6694B22B6436BC43B429958787E45498E78FA8@mssmsx402nb>
Thread-Topic: RE: [PATCH 1/1] indirect function calls elimination in IO scheduler
Thread-Index: AcX2m0zwjdkBx3WSSBKPqIt2qs+fqg==
From: "Ananiev, Leonid I" <leonid.i.ananiev@intel.com>
To: <linux-kernel@vger.kernel.org>
Cc: <axboe@suse.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1341
Lines: 39

Jens,
 
You wrote about patch
>> This breaks reference counting of said
>> structure, so it's not really something that can be applied.
 
>> this patch is a no-go from the beginning since
>> you cannot ref count a statically embedded structure. It has to be
>> dynamically allocated.
 
My answer:
> There was no any 'ref count' elevator structure in 2.6.9. There was
not
> added any 'ref count' while modular and online switching was enabled.
 
>> The does exist outside of the queue getting gotten/put,
>> the switching being one of them. Tejun has patches for improving the
>> switching, so it would be possible to keep two schedulers alive for
the
>> queue for the duration of the switch.
 
Proposed patch does not modify "gotten/put" modules order.
elevator_attch() function dynamically fills 'kmalloced' memory by
elevator structure before patching.
This function  fills substructure after patching dynamically as well.
There is no reference count problem: we can return to old scheduler if
new one fails.
Both, old and new, schedulers are saved for the duration of the switch.
 
Leonid

 
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