From: Jens Axboe <axboe@kernel.dk>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Mike Miller <mike.miller@hp.com>, Don Brace <don.brace@pmcs.com>,
iss_storagedev@hp.com, storagedev@pmcs.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cciss: Optimize scan_thread
Date: Thu, 23 Apr 2015 10:51:59 -0600 [thread overview]
Message-ID: <5539232F.4050404@kernel.dk> (raw)
In-Reply-To: <1429728220.10273.26.camel@stgolabs.net>
On 04/22/2015 12:43 PM, Davidlohr Bueso wrote:
> Two rather small optimizations found while going through driver
> code:
>
> 1) Use the cheaper alternative to set_current_state() as we are
> sure the task will block right afterward.
>
> 2) Checks for list_empty without the scan_mutex. The list_empty
> function is very much designed to work without locks, obviously
> as long as the head (scan_q) is reliable. In this case if another
> thread is doing add_to_scan_list(), we still buckle in the outer
> loop, so it will be caught upon the next iteration -- and if
> kthread_should_stop() hits, it does not matter _anyway_ as we'd
> still need to abort the function regardless of the status of
> the scan_q.
Not that it's wrong, but this is mostly some unneeded optimizations.
It's not like this is in a hot path.
--
Jens Axboe
next prev parent reply other threads:[~2015-04-23 16:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-22 18:43 [PATCH] cciss: Optimize scan_thread Davidlohr Bueso
2015-04-23 16:51 ` Jens Axboe [this message]
2015-04-23 17:06 ` Davidlohr Bueso
2015-04-23 17:11 ` Jens Axboe
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