v2.1's imap/pop3 processes are linked with OpenSSL by default, because of imapc/pop3c storages. I wonder if you notice any actual (system-global) memory usage reduction when compiling without those and you have thousands of imap processes? ./configure --with-storages=mdbox sdbox maildir mbox cydir I guess I could try it myself also but maybe someone else wanting to reduce memory usage is quicker? :) Related to that, you can look at where imap processes' memory goes with: http://dovecot.org/tools/linux-maps-parse-imap.pl I don't know how much memory those (writable!) file-backed memory areas actually use per-process. Maybe nothing, maybe something..
Only have 650 imap clients this weekend, have to give it a try during
a weekday.
Total(MB) Avg(kB) Name
2 4 /lib/ld-2.11.1.so
2 4 /lib/libbz2.so.1.0.4
2 4 /lib/libc-2.11.1.so
63 96 /lib/libcrypto.so.0.9.8
2 4 /lib/libdl-2.11.1.so
0 0 /lib/libnss_dns-2.11.1.so
0 0 /lib/libnss_files-2.11.1.so
2 4 /lib/libpthread-2.11.1.so
0 0 /lib/libresolv-2.11.1.so
2 4 /lib/librt-2.11.1.so
13 20 /lib/libssl.so.0.9.8
2 4 /lib/libz.so.1.2.3.3
2 4 /usr/lib/dovecot/imap
10 16 /usr/lib/dovecot/libdovecot-storage.so.0.0.0
2 4 /usr/lib/dovecot/libdovecot.so.0.0.0
2 4 /usr/lib/dovecot/modules/lib10_quota_plugin.so
2 4 /usr/lib/dovecot/modules/lib11_imap_quota_plugin.so
2 4 /usr/lib/dovecot/modules/lib20_zlib_plugin.so
2 4 /usr/lib/dovecot/modules/lib30_imap_zlib_plugin.so
435 661 [anonymous]
640 973 [heap]
55 84 [stack]
1253 58352 TOTAL
Quoting Timo Sirainen <tss at iki.fi>:
> v2.1's imap/pop3 processes are linked with OpenSSL by default,
> because of imapc/pop3c storages. I wonder if you notice any actual
> (system-global) memory usage reduction when compiling without those
> and you have thousands of imap processes?
>
> ./configure --with-storages=mdbox sdbox maildir mbox cydir
>
> I guess I could try it myself also but maybe someone else wanting to
> reduce memory usage is quicker? :)
>
> Related to that, you can look at where imap processes' memory goes
> with: http://dovecot.org/tools/linux-maps-parse-imap.pl
> I don't know how much memory those (writable!) file-backed memory
> areas actually use per-process. Maybe nothing, maybe something..
On Tue, 2012-09-11 at 21:43 +0300, Timo Sirainen wrote:> v2.1's imap/pop3 processes are linked with OpenSSL by default, because of imapc/pop3c storages. I wonder if you notice any actual (system-global) memory usage reduction when compiling without those and you have thousands of imap processes? > > ./configure --with-storages=mdbox sdbox maildir mbox cydir > > I guess I could try it myself also but maybe someone else wanting to reduce memory usage is quicker? :) > > Related to that, you can look at where imap processes' memory goes with: http://dovecot.org/tools/linux-maps-parse-imap.pl > I don't know how much memory those (writable!) file-backed memory areas actually use per-process. Maybe nothing, maybe something..http://dovecot.org/tmp/proctest.sh can be used to easily test this. Looks like simply linking a binary with -lcrypto increases each process's memory usage by something like: * RHEL5: 50 kB * RHEL6/Debian/Ubuntu: 150-200 kB * Solaris: 100 kB * OpenBSD: 20 kB * OSX: 0 kB Looks like it's the linker that uses up all of this memory. I'm not sure why exactly though, I couldn't create a test library that had the same effect. I also tried imap binary that was statically built vs. linked with libdovecot*.so, and the difference was pretty small (.so used maybe 10-20k more). Anyway, looks like Dovecot can't link OpenSSL to imap/pop3 processes without wasting a ton of memory. In v2.2 I already moved imapc/pop3c backend code to plugins to avoid this. Looks like similar ugliness is needed for other features/backends also that may end up using SSL code. (We were wondering with Stephan what to do about his new HTTP library code that added support for SSL. It would be nice to keep it in the core libdovecot.so, but not if it links with SSL. So looks like we'll need some kind of a http-ssl plugin that is loaded only when needed.)