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SubjectRe: ext3 throughput woes on certain (possibly heavily fragmented) files
On Mon, Sep 16, 2002 at 03:39:11PM -0700, Simon Kirby wrote:
> This box is primarily running a POP3 server (written in-house to cache
> mbox offsets, so that it can handle a huge volume of mail), and also
> exports the mail spool via NFS to other servers which run exim (-fsync).
> nfsd is exported async. Everything is mounted noatime, nodiratime. No
> applications should be calling sync/fsync/fdatasync or using O_SYNC.
> It's a mail server, so everything is fragmented.
> We're using dotlocking. Would this cause metadata journalling? We had
> to hash the mail spool a long time ago do to system time eating all CPU
> (the ext2 linear directory scan to find a slot available in the spool
> directory to add the dotlock file). I estimate about 200 - 300 dotlock
> files are created per second, but these should all be asynchronous.
> Would switching to fctnl() locking (if this works over NFS) solve the
> problem?

I'd absolutly go to fcntl(). As bad as dotlocking is for
journaling filesystems it is even worse for NFS (when it works).
Look at the lkml thread "invalidate_inode_pages in 2.5.32/3"
to get an idea. Multiply the directory invalidations by the
size of the directories. fcntl() is the preferred way of locking
over NFS as it will even report if there is a problem with

J.W. Schultz Pegasystems Technologies
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