On Fri, Sep 17, 2010 at 09:22:00AM -0500, Christoph Lameter wrote: > On Sat, 18 Sep 2010, Bron Gondwana wrote: > > > > From the first look that seems to be the problem. You do not need to be > > > bound to a particular cpu, the scheduler will just leave a single process > > > on the same cpu by default. If you then allocate all memory only from this > > > process then you get the scenario that you described. > > > > Huh? Which bit of forking server makes you think one process is allocating > > lots of memory? They're opening and reading from files. Unless you're > > calling the kernel a "single process". > > I have no idea what your app does. Ok - Cyrus IMAPd has been around for ages. It's an open source email server built on a very traditional single-process model. * a master process which reads config files and manages the other process * multiple imapd processes, one per connection * multiple pop3d processes, one per connection * multiple lmtpd processes, one per connection * periodical "cleanup" processes. Each of these is started by the lightweight master forking and then execing the appropriate daemon. In our configuration we run 20 separate "master" processes, each managing a single disk partition's worth of email. The reason for this is reduced locking contention for the central mailboxes database, and also better replication concurrency, because each instance runs a single replication process - so replication is sequential. > The data that I glanced over looks as > if most allocations happen for a particular memory node Sorry, which data? > and since the > memory is optimized to be local to that node other memory is not used > intensively. This can occur because of allocations through one process / > thread that is always running on the same cpu and therefore always > allocates from the memory node local to that cpu. As Rob said, there are thousands of independent processes, each opening a single mailbox (3 separate metadata files plus possibly hundreds of individual email files). It's likely that diffenent processes will open the same mailbox over time - for example an email client opening multiple concurrent connections, and at the same time an lmtpd connecting and delivering new emails to the mailbox. > It can also happen f.e. if a driver always allocates memory local to the > I/O bus that it is using. None of what we're doing is super weird advanced stuff, it's a vanilla forking daemon where a single process run and does stuff on behalf of a user. The only slightly interesting things: 1) each "service" has a single lock file, and all the idle processes of that type (i.e. imapd) block on that lock while they're waiting for a connection. This is to avoid thundering herd on operating systems which aren't nice about it. The winner does the accept and handles the connection. 2) once it's finished processing a request, the process will wait for another connection rather than closing. Nothing sounds like what you're talking about (one giant process that's all on one CPU), and I don't know why you keep talking about it. It's nothing like what we're running on these machines. Bron. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>