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Date: Sat, 23 Feb 2008 00:06:09 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Peter Zijlstra <a.p.zijlstra@...llo.nl> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, netdev@...r.kernel.org, trond.myklebust@....uio.no Subject: Re: [PATCH 15/28] netvm: network reserve infrastructure On Wed, 20 Feb 2008 15:46:25 +0100 Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote: > Provide the basic infrastructure to reserve and charge/account network memory. > > We provide the following reserve tree: > > 1) total network reserve > 2) network TX reserve > 3) protocol TX pages > 4) network RX reserve > 5) SKB data reserve > > [1] is used to make all the network reserves a single subtree, for easy > manipulation. > > [2] and [4] are merely for eastetic reasons. > > The TX pages reserve [3] is assumed bounded by it being the upper bound of > memory that can be used for sending pages (not quite true, but good enough) > > The SKB reserve [5] is an aggregate reserve, which is used to charge SKB data > against in the fallback path. > > The consumers for these reserves are sockets marked with: > SOCK_MEMALLOC > > Such sockets are to be used to service the VM (iow. to swap over). They > must be handled kernel side, exposing such a socket to user-space is a BUG. > > +/** > + * sk_adjust_memalloc - adjust the global memalloc reserve for critical RX > + * @socks: number of new %SOCK_MEMALLOC sockets > + * @tx_resserve_pages: number of pages to (un)reserve for TX > + * > + * This function adjusts the memalloc reserve based on system demand. > + * The RX reserve is a limit, and only added once, not for each socket. > + * > + * NOTE: > + * @tx_reserve_pages is an upper-bound of memory used for TX hence > + * we need not account the pages like we do for RX pages. > + */ > +int sk_adjust_memalloc(int socks, long tx_reserve_pages) > +{ > + int nr_socks; > + int err; > + > + err = mem_reserve_pages_add(&net_tx_pages, tx_reserve_pages); > + if (err) > + return err; > + > + nr_socks = atomic_read(&memalloc_socks); > + if (!nr_socks && socks > 0) > + err = mem_reserve_connect(&net_reserve, &mem_reserve_root); This looks like it should have some locking? > + nr_socks = atomic_add_return(socks, &memalloc_socks); > + if (!nr_socks && socks) > + err = mem_reserve_disconnect(&net_reserve); Or does that try to make up for it? Still looks fishy. > + if (err) > + mem_reserve_pages_add(&net_tx_pages, -tx_reserve_pages); > + > + return err; > +} > + > +/** > + * sk_set_memalloc - sets %SOCK_MEMALLOC > + * @sk: socket to set it on > + * > + * Set %SOCK_MEMALLOC on a socket and increase the memalloc reserve > + * accordingly. > + */ > +int sk_set_memalloc(struct sock *sk) > +{ > + int set = sock_flag(sk, SOCK_MEMALLOC); > +#ifndef CONFIG_NETVM > + BUG(); > +#endif ?? #error, maybe? > + if (!set) { > + int err = sk_adjust_memalloc(1, 0); > + if (err) > + return err; > + > + sock_set_flag(sk, SOCK_MEMALLOC); > + sk->sk_allocation |= __GFP_MEMALLOC; > + } > + return !set; > +} > +EXPORT_SYMBOL_GPL(sk_set_memalloc); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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