From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steve French <smfltc@us.ibm.com>
Subject: Re: [RFC/PATCH] - revert generic_fillattr stat->blksize to	 	PAGE_CACHE_SIZE
Date: Tue, 07 Nov 2006 09:50:27 -0600
Message-ID: <4550AB43.10704@us.ibm.com>
References: <454FAE0A.3070409@redhat.com>	 <1162852069.11030.70.camel@kleikamp.austin.ibm.com>	 <454FD2BE.2090302@us.ibm.com>	 <1162906845.8123.11.camel@kleikamp.austin.ibm.com> <1162913653.8123.13.camel@kleikamp.austin.ibm.com>
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Cc: Eric Sandeen <sandeen@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Theodore Tso <tytso@mit.edu>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S932681AbWKGPtd@vger.kernel.org>
To: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
In-Reply-To: <1162913653.8123.13.camel@kleikamp.austin.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

Dave Kleikamp wrote:
> On Tue, 2006-11-07 at 07:40 -0600, Dave Kleikamp wrote:
>   
>> It would probably be best to just set stat->blksize to the negotiated
>> buffer size.
>>     
>
> But be careful here.  I don't know how applications/glibc may behave if
> stat->blksize is not a power of 2.
>   
The man page is not particularly helpful either as it simply indicates:
    "The st_blksize field gives the preferred blocksize for efficient 
file system  I/O. "
but it appears that blksize would affects readdir performance more than 
read/write
(since read/write go through the pagecache and thus readpages/writepages
will request readahead/writebehind for many pages at a time) unless the 
application
opens the file direct i/o.