On Thu, Apr 16, 2015 at 8:01 AM, David Herrmann <dh.herrm...@gmail.com> wrote: > Hi > > On Thu, Apr 16, 2015 at 4:34 PM, Andy Lutomirski <l...@amacapital.net> wrote: >> Whose memcg does the pool use? > > The pool-owner's (i.e., the receiver's). > >> If it's the receiver's, and if the >> receiver can configure a memcg, then it seems that even a single >> receiver could probably cause the sender to block for an unlimited >> amount of time. > > How? Which of those calls can block? I don't see how that can happen.
I admit I don't fully understand memcg, but vfs_iter_write is presumably going to need to get write access to the target pool page, and that, in turn, will need that page to exist in memory and to be writable, which may need to page it in and/or allocate a page. If that uses the receiver's memcg (as it should), then the receiver can make it block. Even if it doesn't use the receiver's memcg, it can trigger direct reclaim, I think. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
