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Date:      Fri, 8 Nov 2002 10:35:27 -0800
From:      Alfred Perlstein <bright@mu.org>
To:        vishal mittal <vm2908tml@yahoo.com>
Cc:        freebsd-fs@FreeBSD.ORG
Subject:   Re: Question regarding filesystem performance
Message-ID:  <20021108183527.GN39178@elvis.mu.org>
In-Reply-To: <20021108182420.5418.qmail@web13207.mail.yahoo.com>
References:  <20021108182420.5418.qmail@web13207.mail.yahoo.com>

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* vishal mittal <vm2908tml@yahoo.com> [021108 10:24] wrote:
> Hi,
> 
> I am working on a 4.4-RELEASE. I have about 30,000 1K
> files in a directory. Any delete or move operation on
> a file in this directory introduces unacceptable
> delays in some other time-critical processes that I am
> running on the machine.
> 
> I am assuming that the delay is because of the large
> number of files due to which it takes a longer time to
> update the inode information and, delete and move
> being atomic operations, they do not relinquish the
> CPU for the other processes during that time.

No.  The problem is that each operation causes linear
searches on the directory contents which is expensive.

> If the problem is what I think it is then is there a
> way to overcome this problem by tuning some parameter
> or something?

Yes, by using the UFS_DIRHASH kernel option, however
I really recommend that you upgrade to a more recent
version of FreeBSD 4, (4.7) because the version of
the code for UFS_DIRHASH in 4.4 is marked experimental
and may not be stable.

-- 
-Alfred Perlstein [alfred@freebsd.org]
'Instead of asking why a piece of software is using "1970s technology,"
 start asking why software is ignoring 30 years of accumulated wisdom.'

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