Date: Wed, 3 Sep 2008 17:03:21 +0530 From: "Sujit Karataparambil" <sjt.kar@gmail.com> Cc: freebsd-stable@freebsd.org Subject: Re: vfs.ffs.rawreadahead Message-ID: <921ca19c0809030433w50e16100rd624cdb4a2e4e947@mail.gmail.com> In-Reply-To: <20080903112512.GB62541@rambler-co.ru> References: <20080903095352.GA62541@rambler-co.ru> <921ca19c0809030333u6accf415l80ec5bfb4a984ce1@mail.gmail.com> <20080903112512.GB62541@rambler-co.ru>
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These are Journalling File System. Some thing like WAPBL which stands for Write-Ahead Physical Block Logging. These are built on Generic kernel components. On 9/3/08, Igor Sysoev <is@rambler-co.ru> wrote: > On Wed, Sep 03, 2008 at 04:03:59PM +0530, Sujit Karataparambil wrote: > > > The VFS was designed to be Object abtraction of the Berkeley Fast File System. > > This has been since an terminology with journalling filesystem to have > > functionality to added on request. > > In src/sys/ufs/ffs/ffs_rawread.c I see that rawreadahead is used. > However, I do not understand whether rawreadahead starts a second > parallel ahead disk transaction with supplied userland buffer or not. > > > -- > Igor Sysoev > http://sysoev.ru/en/ > > > On 9/3/08, Igor Sysoev <is@rambler-co.ru> wrote: > > > Hi, > > > > > > could anyone tell what does vfs.ffs.rawreadahead enable ? > > > As I understand it's used in DIRECTIO code that allows read data > > > directly to an userland buffer bypassing the buffer cache. > > > What I can not understand where the read ahead data can be placed in ? > > > > > > > > > -- > > > Igor Sysoev > > > http://sysoev.ru/en/ > -- --linux(2.4/2.6),bsd(4.5.x+),solaris(2.5+)
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