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Date:   Fri, 28 Feb 2020 14:32:48 -0500
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Ian Kent <raven@themaw.net>, Andreas Dilger <adilger@dilger.ca>,
        Waiman Long <longman@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jonathan Corbet <corbet@lwn.net>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        linux-doc@vger.kernel.org,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Eric Biggers <ebiggers@google.com>,
        Dave Chinner <david@fromorbit.com>,
        Eric Sandeen <sandeen@redhat.com>
Subject: Re: [PATCH 00/11] fs/dcache: Limit # of negative dentries
Message-ID: <20200228193248.GE101220@mit.edu>
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On Thu, Feb 27, 2020 at 07:34:12PM -0800, Matthew Wilcox wrote:
> 
> The canonical argument in favour of negative dentries is to improve
> application startup time as every application searches the library path
> for the same libraries.

The other canonical example is C compilers that need to search for
header files along the include search path:

% strace  -o /tmp/st -f gcc -o /tmp/hello /tmp/hello.c -I.. -I../..
% grep open /tmp/st | grep stdio.h | grep ENOENT | wc -l
6

						- Ted