linux-kernel - Re: [PATCH RESEND] fs: Move bh_cachep to the __read

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Message-ID: <CAK-9PRBi3XOVtW3gs3doO=ecD0XWfNffVefdRCC1sGnLdT_9LA@mail.gmail.com>
Date:	Mon, 2 Jul 2012 23:54:09 +0530
From:	Chinmay V S <cvs268@...il.com>
To:	Vlad Zolotarov <vlad@...lemp.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Shai@...lemp.com
Subject: Re: [PATCH RESEND] fs: Move bh_cachep to the __read_mostly section

Hi Vlad,

I suppose we both are looking at opposite sides of the same coin.
While i am wary of the potential pitfalls,
you have focused on the benefits of using __read_mostly.

At this point i would like to send out a shout to everyone concerned to please
clarify the status of __read_mostly:

1. Is it being actively pursued? (systems that *will* clearly benefit from it)
2. Any actual results on real world use-cases? (w/ & w/o __read_mostly)
3. Is __read_mostly being accepted in non-architecture specific kernel code?
4. Is anyone working on a potential replacement for it?

regards
ChinmayVS

>I think your point is clear and has actually been nicely stated at
>thecodeartist.blogspot.com/2011/12/why-readmostly-does-not-work-as-it.htm
>(by u? :))

PS: Yes, the link i referred to *is* indeed my own article that i posted a few
months ago after my experiments with __read_mostly. I was initially excited when
i found this bit while digging through the code. But upon seeing that an entire
arch had disabled it, and then understanding why, i feel its usage needs to be
restricted to arch specific code and even then thoroughly tested too.
(then again, i may be wrong.)
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