From: Linus Torvalds <torvalds@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Jonathan Corbet <corbet@lwn.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
"Luis R. Rodriguez" <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>, Jan Kara <jack@suse.cz>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Miklos Szeredi <mszeredi@redhat.com>,
Larry Woodman <lwoodman@redhat.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"Wangkai (Kevin,C)" <wangkai86@huawei.com>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 2/2] fs/dcache: Make negative dentries easier to be reclaimed
Date: Tue, 28 Aug 2018 16:10:24 -0700 [thread overview]
Message-ID: <CA+55aFxy1vH2CamZ_pdFohKgSJgi1i2MkeaY1qX8NdFK8Xu8Ww@mail.gmail.com> (raw)
In-Reply-To: <6873378b-3202-e738-2366-5fb818b4a013@redhat.com>
On Tue, Aug 28, 2018 at 3:29 PM Waiman Long <longman@redhat.com> wrote:
>
> Yes, I can rewrite it. What is the problem with the abbreviated form?
Either gcc rewrites it for you, or you end up _actually_ using a
function pointer and calling through it.
The latter would be absolutely horribly bad for something like
"list_add()", which should expand to just a couple of instructions.
And the former would be ok, except for the "you wrote code the garbage
way, and then depended on the compiler fixing it up". Which we
generally try to avoid in the kernel.
(Don't get me wrong - we definitely depend on the compiler doing a
good job at CSE and dead code elimination etc, but generally we try to
avoid the whole "compiler has to rewrite code to be good" model).
Linus
next prev parent reply other threads:[~2018-08-28 23:10 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-28 17:19 [PATCH 0/2] fs/dcache: Track # of negative dentries Waiman Long
2018-08-28 17:19 ` [PATCH 1/2] fs/dcache: Track & report number " Waiman Long
2018-08-29 0:11 ` Dave Chinner
2018-08-29 17:11 ` Waiman Long
2018-08-30 1:43 ` Dave Chinner
2018-08-30 21:49 ` Waiman Long
2018-08-31 14:31 ` Matthew Wilcox
2018-08-31 15:03 ` Waiman Long
2018-08-28 17:19 ` [PATCH 2/2] fs/dcache: Make negative dentries easier to be reclaimed Waiman Long
2018-08-28 22:13 ` Matthew Wilcox
2018-08-28 22:29 ` Waiman Long
2018-08-28 23:10 ` Linus Torvalds [this message]
2018-08-28 23:22 ` Andrew Morton
2018-08-29 1:18 ` Waiman Long
2018-08-29 1:18 ` Waiman Long
2018-08-28 23:01 ` Andrew Morton
2018-08-29 17:54 ` Paul E. McKenney
2018-08-29 20:03 ` Waiman Long
2018-08-29 21:04 ` Matthew Wilcox
2018-08-29 1:02 ` Dave Chinner
2018-08-29 19:34 ` Waiman Long
2018-08-30 1:12 ` Dave Chinner
2018-08-30 21:51 ` Waiman Long
2018-08-29 7:51 ` Michal Hocko
2018-08-29 19:58 ` Waiman Long
2018-08-30 7:20 ` Michal Hocko
2018-08-30 21:48 ` Waiman Long
2018-08-28 22:50 ` [PATCH 0/2] fs/dcache: Track # of negative dentries Andrew Morton
2018-08-28 22:54 ` Waiman Long
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