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Re: [Nmh-workers] MH-W intro/help request

From: Erich Boleyn
Subject: Re: [Nmh-workers] MH-W intro/help request
Date: Tue, 02 Dec 2014 10:11:18 -0800

Ken Hornstein writes:

> >What I use now is "mark -list -sequence unseen", which returns compressed
> >lists of messages (i.e. "1-5,7-8" instead of "1 2 3 4 5 7 8").  Parsing
> >this to intersect it with my pick output is relatively fast, though it
> >is of course ineligant compared to getting *just* the list you want.  It
> >is also surprisingly slow (like 1/7th of a second to get this vs. other
> >MH programs which run 10x or more faster).  I don't really understand why
> >it is so slow, since it is a near character-for-character copy of the
> >one line that the .mh_sequences file has in it.  If it wasn't so very
> >slow compared to the other MH programs, I probably would not have even
> >brought it up for now.
> You know, I just took a look at it; it should not be slow, actually,
> unless you're running into things like lock contention for the sequence
> file.  It does the same things every other MH program does (it calls
> folder_read()) but then it does very little after that.  Could you
> do a system call trace and try to figure out what's taking so long?

OK, I hadn't really tried to debug it before, but after this comment
I ran some tests.  What I found is that it is not just mark, but
it seems related to the large folder I was testing it on, and some
other MH programs get slow when run under exactly the same circumstances.

Specifically, I was testing it on a very large folder of approx 100K
messages.  Both the "mark ..." and a "show N" invokation take about
the more than 1/10th of a second on average, even for extremely short

        time show 99948 > /dev/null
                real    0m0.120s
                user    0m0.040s
                sys     0m0.068s
        time mark -list -sequence unseen > /dev/null
                real    0m0.123s
                user    0m0.060s
                sys     0m0.060s

The actual output of mark is (just so you know it is very tiny)
        unseen: 99898-99907 99912-99947 99949-99959

The show command is for a minimally small email.

Using "cat" on the same file that takes show more than 1/10th of a
second is comparatively absurdly fast:
        time cat Mail/inbox-old/99948 > /dev/null
                real    0m0.002s
                user    0m0.000s
                sys     0m0.000s

"mark" run on a small folder is quite fast.

But it does seem Weird that it would take so long for these small
operations on a large folder.  Is the "folder_read()" troublesome here?

    Erich Stefan Boleyn     <address@hidden>     http://www.uruk.org/
"Reality is truly stranger than fiction; Probably why fiction is so popular"

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