linux-kernel - Re: Question about Reiser4

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Date:	Tue, 24 Apr 2007 13:15:17 +0200
From:	"Denis Vlasenko" <vda.linux@...glemail.com>
To:	"Theodore Tso" <tytso@....edu>,
	"Eric Hopper" <hopper@...ifarious.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: Question about Reiser4

> Theodore Tso wrote:
> >
> > One of the big problems of using a filesystem as a DB is the system
> > call overheads.  If you use huge numbers of tiny files, then each
> > attempt read an atom of information from the DB takes three system
> > calls --- an open(), read(), and close(), with all of the overheads in
> > terms of dentry and inode cache.
> >
>
> Now, to be fair, there are probably a number of cases where
> open/lseek/readv/close and open/lseek/writev/close would be worth doing
> as a single system call.  The big problem as far as I can see involves
> EINTR handling; such a system call has serious restartability implications.
>
> Of course, there are Ingo's syslets...

I definitely would like open/readv/close syscall a lot.
Actually, a set of four syscalls

open/readv/close
open/pread/close
open/writev/close
open/pwrite/close

will allow to reduce syscall overhead for a number of cases.
--
vda
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