2 years ago I had that type of functionality implemented for Ibrix. It included readdir-ahead and lookup-ahead. We did not assume any new syscalls, simply detected readdir+ like interest on VFS level and pushed a wave of populating directory caches and plugging in dentry cache entries. It improved productivity of NFS readdir+ and SMB QueryDirectories more than 4x. Regards, Boris > -----Original Message----- > From: linux-fsdevel-owner@xxxxxxxxxxxxxxx [mailto:linux-fsdevel- > owner@xxxxxxxxxxxxxxx] On Behalf Of Abhijith Das > Sent: Monday, July 28, 2014 8:22 AM > To: Dave Chinner > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel; cluster-devel > Subject: Re: [RFC] readdirplus implementations: xgetdents vs dirreadahead syscalls > > > > ----- Original Message ----- > > From: "Dave Chinner" <david@xxxxxxxxxxxxx> > > To: "Zach Brown" <zab@xxxxxxxxxx> > > Cc: "Abhijith Das" <adas@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, > > "linux-fsdevel" <linux-fsdevel@xxxxxxxxxxxxxxx>, "cluster-devel" > > <cluster-devel@xxxxxxxxxx> > > Sent: Friday, July 25, 2014 7:38:59 PM > > Subject: Re: [RFC] readdirplus implementations: xgetdents vs > > dirreadahead syscalls > > > > On Fri, Jul 25, 2014 at 10:52:57AM -0700, Zach Brown wrote: > > > On Fri, Jul 25, 2014 at 01:37:19PM -0400, Abhijith Das wrote: > > > > Hi all, > > > > > > > > The topic of a readdirplus-like syscall had come up for discussion > > > > at last year's LSF/MM collab summit. I wrote a couple of syscalls > > > > with their GFS2 implementations to get at a directory's entries as > > > > well as stat() info on the individual inodes. > > > > I'm presenting these patches and some early test results on a > > > > single-node > > > > GFS2 > > > > filesystem. > > > > > > > > 1. dirreadahead() - This patchset is very simple compared to the > > > > xgetdents() system > > > > call below and scales very well for large directories in GFS2. > > > > dirreadahead() is > > > > designed to be called prior to getdents+stat operations. > > > > > > Hmm. Have you tried plumbing these read-ahead calls in under the > > > normal > > > getdents() syscalls? > > > > The issue is not directory block readahead (which some filesystems > > like XFS already have), but issuing inode readahead during the > > getdents() syscall. > > > > It's the semi-random, interleaved inode IO that is being optimised > > here (i.e. queued, ordered, issued, cached), not the directory blocks > > themselves. As such, why does this need to be done in the kernel? > > This can all be done in userspace, and even hidden within the > > readdir() or ftw/ntfw() implementations themselves so it's OS, kernel > > and filesystem independent...... > > > > I don't see how the sorting of the inode reads in disk block order can be accomplished in > userland without knowing the fs-specific topology. From my observations, I've seen that > the performance gain is the most when we can order the reads such that seek times are > minimized on rotational media. > > I have not tested my patches against SSDs, but my guess would be that the > performance impact would be minimal, if any. > > Cheers! > --Abhi > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a > message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
