Re: Maildir ext4 slowness
On 4/8/2014 9:47 PM, Kumar Appaiah wrote:
> Dear Debian User,
>
> Of late, I've observed that opening my Maildir boxes in Mutt has been
> a tad slow. Here is the rough structure:
>
> I have an LVM home directory (ext4), within which I have a folder
> called ~/Maildir. This folder has several Maildirs, say inbox,
> debian-user etc., each of which gets its mail delivered using
> procmail.
>
> tune2fs gives me these features: has_journal ext_attr resize_inode
> dir_index filetype needs_recovery extent flex_bg sparse_super
> large_file huge_file uninit_bg dir_nlink extra_isize
>
> Of late, I've observed that folders with over 1000 messages seem quite
> slow to respond (order of 3-4 seconds), which wasn't really happening
> in the old days when I was using mboxes. I prefer Maildir since I can
> use notmuch to index my mails easily.
>
> Is there something I could to to speed things up? For instance, I
> could create a 20 GB file, create another filesystem on it and mount
> it as my Maildir, if that would help.
Sparse files tend to fragment horribly, especially on EXT4, and this
will be exacerbated by storing maildir files in it. So this is not your
solution. If anything it would be worse than now.
As with any MUA directly accessing maildir files performance gradually
slows down over time with more and more mail files because they are
scattered across the filesystem, especially with EXT, much less so with
XFS. Seeking to 1000 files all over the disk to read the headers takes
time. mbox is quicker because you typically have far more messages
stored linearly on disk, thus you have much less seeking when reading
headers.
Mutt, as with other MUAs, creates a header cache so it only needs to
read the headers of new mail files. If you're slowing down with large
maildir folders, the most likely problem is that your header caching is
not working properly. I am not a mutt user so I cannot tell you which
knob to turn or which cache file to delete/recreate to fix this. I have
seen the same problem with many other MUAs and this is most often the
cause. See this thread from '08 for background on the excessive
seeking. The patch for this should already be in your mutt version if
it's current, but understanding what is being discussed may give you an
idea as to what is broken, and where to start looking:
http://lkml.iu.edu//hypermail/linux/kernel/0812.2/00514.html
Cheers,
Stan
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