Date: Fri, 28 Sep 2001 10:58:29 +0300 From: Ruslan Ermilov <ru@FreeBSD.ORG> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Julian Elischer <julian@vicor-nb.com>, current@FreeBSD.ORG Subject: Re: RFC: mod for 'du' Message-ID: <20010928105829.F30062@sunbay.com> In-Reply-To: <69645.1001658209@critter>; from phk@critter.freebsd.dk on Fri, Sep 28, 2001 at 08:23:29AM %2B0200 References: <3BB3936A.D1E1F6B3@vicor-nb.com> <69645.1001658209@critter>
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We even have a working hcreate(3) and friends in 5.0-CURRENT,
that could probably be tried as well. Will MFC shortly.
On Fri, Sep 28, 2001 at 08:23:29AM +0200, Poul-Henning Kamp wrote:
> In message <3BB3936A.D1E1F6B3@vicor-nb.com>, Julian Elischer writes:
> >This is a multi-part message in MIME format.
> >--------------5937F02517145C712E28C299
> >Content-Type: text/plain; charset=us-ascii
> >Content-Transfer-Encoding: 7bit
> >
> >'du' keeps an array of files it has encountered that have > 1 link.
> >Whenever it encounters another, it checks to see if it's one it has
> >already seen
> >and thus can avoid counting its space twice..
> >
> >This is ok for small filesystems, however VICOR maintains
> >500GB filesystems on which much of the data has several links.
> >
> >The following patch to replace the linear array (which it realocs if too
> >small)
> >(which it scans linearly) with a hash-table can makle a DRASTIC change
> >to how DU perfomrs for us in this environment.
> >
> >In a small test, we made a linked copy of /usr/src
> >
> >the run times were:
> >old: 0.410u 2.221s 1:55.41 2.2% 12+1355k 6325+0io 2pf+0w
> >new: 8.610u 2.665s 2:09.23 8.7% 10+718k 6367+0io 2pf+0
>
> Have you examined if the hask key is evenly distributed ?
>
> >Does anyone have objections to me committing this (or a variant of it)?
>
> I would certainly have objections of you show us one patch and
> commit another..
>
> > * The Regents of the University of California. All rights reserved.
> > *
> >+ * This version of du has been modified by Andre de Bruin and Scott Macy for Vicor.
>
> Too long line ?
>
> >+ * The change is related to the handling of file links, in the official
> >+ * release, du keeps a simple linked list of all visited i-nodes with
> >+ * multiple links. This list is now implemented as a "hash table" (actually
> >+ * a fixed size array) with link list nodes providing a
> >+ * performance of up to 30% better than the original version.
> >+ * The only changes are in file create.c and marked with "AdB".
>
> We put such stuff in the CVS commit message, not in the source file.
>
> >+typedef struct _ID {
> >+ dev_t dev;
> >+ ino_t inode;
> >+ struct _ID *next;
> >+} ID;
>
> Why not use db(3) ?
>
> It has a known good hash, it autosizes to different task-sets and
> it could be setup with an option to put the hash-table in a diskfile
> ("du -t" ?) for known bad cases of many hardlinks
--
Ruslan Ermilov Oracle Developer/DBA,
ru@sunbay.com Sunbay Software AG,
ru@FreeBSD.org FreeBSD committer,
+380.652.512.251 Simferopol, Ukraine
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