Date: Thu, 22 Oct 2009 18:33:52 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: John Baldwin <jhb@freebsd.org> Cc: arch@freebsd.org Subject: Re: Put a timeout on -ve name cache entries in NFS Message-ID: <20091022182943.P13634@delplex.bde.org> In-Reply-To: <200910191634.30040.jhb@freebsd.org> References: <200910191634.30040.jhb@freebsd.org>
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On Mon, 19 Oct 2009, John Baldwin wrote: > This patch allows one to put an upper time limit on how long the NFS client > should keep negative cache entries around for a given directory. This is > basically a safety belt as there are certain races with -ve entries that are > not easily fixed (e.g. dealing with the low resolution of the directory > modification timestamps). However, timing out the entries would put a limit > on how stale the client's cache entries could be. My main question is do > folks think this value should be tunable as a global sysctl or a per-mount > option. A sysctl is far easier to implement (and the acccess cache timeout > is a sysctl). However, the other namecache-related settings are all mount > options, so a mount option might be more consistent. Current rough patch is > below: One reason that I never committed my port of NetBSD's implementation of negative cache entries for nfs is that I thought the timeout should be a mount option but I didn't want to deal with the portability problems from that. Bruce
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