[Dovecot] severe performance problem (mail cache related?)

[Dan Price]

On Wed 14 Feb 2007 at 02:24PM, Dan Price wrote:
> write(1, " *   1 0 7 9 5   F E T C".., 2050)    = 2050
> mmap64(0x00000000, 7356416, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0) = 0xFD800000
> munmap(0xFE602000, 1048576)                     = 0
> munmap(0xFE502000, 1048576)                     = 0
> munmap(0xFE402000, 1048576)                     = 0
> munmap(0xFE302000, 1048576)                     = 0
> munmap(0xFE202000, 1048576)                     = 0
> munmap(0xFE102000, 1048576)                     = 0
> munmap(0xFE002000, 1048576)                     = 0
> munmap(0xFE000000, 8192)                        = 0

I was sad to see no response about this issue.  I'm now seeing this
on my *own* mailbox which is disturbing.  Here is an example:

pread64(9, " p o s a l s\n\0\0\0\013".., 8192, 7241728) = 8192
pread64(9, "   < S t e v e n . L u c".., 8192, 7249920) = 8192
pread64(9, "\0\0\01F\0\0\0\0 T o :  ".., 8192, 7258112) = 8192
mmap64(0x00000000, 13058048, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0) = 0xFE400000
munmap(0xFDF72000, 1048576)                     = 0
munmap(0xFDE72000, 1048576)                     = 0
munmap(0xFDD72000, 1048576)                     = 0
munmap(0xFDC72000, 1048576)                     = 0
munmap(0xFDB72000, 1048576)                     = 0
munmap(0xFDA72000, 1048576)                     = 0
munmap(0xFD972000, 1048576)                     = 0
munmap(0xFD872000, 1048576)                     = 0
munmap(0xFD772000, 1048576)                     = 0
munmap(0xFD672000, 1048576)                     = 0
munmap(0xFD572000, 1048576)                     = 0
munmap(0xFD472000, 1048576)                     = 0
munmap(0xFD402000, 458752)                      = 0
munmap(0xFD400000, 8192)                        = 0

So here we see dovecot allocate a whopping 12MB of anonymous memory,
then munmap it all away in 1MB chunks.

Timo, do you know why this is happening?  It is ruining performance for me.

        -dp

-- 
Daniel Price - Solaris Kernel Engineering - dp at eng.sun.com - blogs.sun.com/dp