Date: Wed, 25 May 2005 09:34:31 +0200
From: Jens Axboe <axboe@suse.de>
To: Tejun Heo <htejun@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH Linux 2.6.12-rc4-mm2 00/03] cfq: various fixes
Message-ID: <20050525073429.GA13068@suse.de>
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On Wed, May 25 2005, Tejun Heo wrote:
>  Hello, Jens.
> 
>  This patchset is various fixes to cfq.  All patches are against
> 2.6.12-rc4-mm2.
> 
>  One thing that isn't fixed in this patchset but I think might be
> problematic is the priority of async queue.  It seems that the async
> queue doesn't receive any special attention regarding its priority.
> It just follows normal rules and its priority jumps irregularly.
> If I'm missing something, plz point out.
> 
> [ Start of patch descriptions ]
> 
> 01_cfq_INSERT_BACK_fix.patch
> 	: cfq ELEVATOR_INSERT_BACK fix
> 
> 	When inserting INSERT_BACK request, cfq_insert_request() calls
> 	cfq_dispatch_requests() repetitively until it returns zero
> 	indicating no request is dispatched.  This used to flush all
> 	the requests in the queue to the dispatch queue but, with idle
> 	slice implemented, the current active queue may decide to wait
> 	for new request using slice_timer.  When this happens, 0 is
> 	returned from cfq_dispatch_requests() even when other cfqq's
> 	have pending requests.  This breaks INSRET_BACK semantics.
> 
> 	This patch adds @force argument which, when set to non-zero,
> 	disables idle_slice, and uses the argument when flushing
> 	cfqq's for INSERT_BACK.  While at it, use INT_MAX instead of
> 	cfq_quantum when flushing cfqq's, as we're gonna dump all the
> 	requests and using cfq_quantum does nothing but adding
> 	unnecessary iterations.
> 
> 02_cfq_ioc_leak_fix.patch
> 	: cfq_io_context leak fix
> 
> 	When a process has more than one cic's associated with it,
> 	only the first one was kmem_cache_free'd in the original code.
> 	This patch frees all cic's in cfq_free_io_context().
> 
> 	While at it, remove unnecessary refcounting from cic's to ioc.
> 	This reference is created when each cic is created and removed
> 	altogether when the ioc is exited, and, thus, serves no
> 	purpose.
> 
> 03_cfq_remove_unused_fields.patch
> 	: remove serveral unused fields from cfq data structures
> 
> 	cfq_data->idle_start, cfq_data->end_prio and cfq_rq->end_pos
> 	are not used in meaningful way.  Remove'em.

All three patches look good, thanks!

-- 
Jens Axboe

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