[Top] [All Lists]

Re: Advice sought on how to lock multiple pages in ->prepare_write and -

To: Nathan Scott <nathans@xxxxxxx>
Subject: Re: Advice sought on how to lock multiple pages in ->prepare_write and ->writepage
From: Bryan Henderson <hbryan@xxxxxxxxxx>
Date: Mon, 31 Jan 2005 15:46:15 -0800
Cc: Anton Altaparmakov <aia21@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-xfs@xxxxxxxxxxx, viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
In-reply-to: <20050131220002.GB9377@frodo>
Sender: linux-xfs-bounce@xxxxxxxxxxx
>OOC, have you folks measured any performance improvements at all
>using larger IOs (doing multi-page bios?) with larger blocksizes?

First, let me clarify that by "larger I/O" you mean a larger unit of I/O 
submitted to the block layer (doing multi-page bios), because people often 
say "larger I/O" to mean larger units of I/O from Linux to the device, and 
the two are only barely coupled.

Blocksize > page size doesn't mean multi-page bios as long as VM is still 
managing the file cache.  VM pages in and out one page at a time.

To get multi-page bios (in any natural way), you need to throw out not 
only the generic file read/write routines, but the page cache as well.

Every time I've looked at multi-page bios, I've been unable to see any 
reason that they would be faster than multiple single-page bios.  But I 
haven't seen any experiments.

Bryan Henderson                     IBM Almaden Research Center
San Jose CA                         Filesystems  

<Prev in Thread] Current Thread [Next in Thread>