[OpenAFS-devel] more on the 2.2.18pre17 SMP cpu hog/etc.

[Nathan Neulinger]

(Reiserfs list: this is cc'd from openafs-devel - related to a problem
I've been having with really poor performance of afsd startup.)

Well, I've narrowed down the problem to a specific location in the code.

After the first time, it worked almost instantly. The first time through
though, this call in LINUX/osi_file.c

        MYDEBUG("G");
    tip = iget(afs_cacheSBp, (u_long)ainode);
        MYDEBUG("H");

that call takes TWELVE jiffies when it's slow. (Mydebug just prints out
a jiffies count with a label.)

So, it seems to me that it might just be an issue with the particular
version of reiserfs or with the kernel. I'm running 3.5.25 on 2.2.17 at
work, 3.5.27 with 2.2.18pre17 at home. I do know that the filesystem at
work is using the tea hash, and at home is using r5 hash.

(Reiserfs list: the files are named /afscache/V0 - /afscache/V99, there
are 102 files in the directory.)

Any ideas?

-- Nathan

Nathan Neulinger wrote:
> 
> Ok. I've done some more testing.
> 
> I added some extra debugging to afsd in the CACHEINODE loop, including
> some fflush()'s. That loop is running incredibly slowly.
> 
> Now, here's the interesting part. If I unmount /afs, rmmod, and then try
> the whole thing again, the second time it runs through that loop
> instantly. In both cases, the cache already exists. (Removing the cache
> has no impact.)
> 
> I'm instrumenting some more stuff further, will see if I find anything.
> 
> -- Nathan
> 
> ------------------------------------------------------------
> Nathan Neulinger                       EMail:  nneul@umr.edu
> University of Missouri - Rolla         Phone: (573) 341-4841
> CIS - Systems Programming                Fax: (573) 341-4216
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-- 


------------------------------------------------------------
Nathan Neulinger                       EMail:  nneul@umr.edu
University of Missouri - Rolla         Phone: (573) 341-4841
CIS - Systems Programming                Fax: (573) 341-4216