From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC][PATCH 3/4] deadlock prevention core From: Peter Zijlstra In-Reply-To: <57504.81.207.0.53.1155407532.squirrel@81.207.0.53> References: <20060812141415.30842.78695.sendpatchset@lappy> <20060812141445.30842.47336.sendpatchset@lappy> <44640.81.207.0.53.1155403862.squirrel@81.207.0.53> <1155404697.13508.81.camel@lappy> <40048.81.207.0.53.1155405282.squirrel@81.207.0.53> <1155406120.13508.87.camel@lappy> <57504.81.207.0.53.1155407532.squirrel@81.207.0.53> Content-Type: text/plain Date: Sat, 12 Aug 2006 20:47:11 +0200 Message-Id: <1155408431.13508.110.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Indan Zupancic Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Evgeniy Polyakov , Daniel Phillips , Rik van Riel , David Miller List-ID: On Sat, 2006-08-12 at 20:32 +0200, Indan Zupancic wrote: > On Sat, August 12, 2006 20:08, Peter Zijlstra said: > > On Sat, 2006-08-12 at 19:54 +0200, Indan Zupancic wrote: > >> True, but currently memalloc_reserve isn't used in a sensible way, > >> or I'm missing something. > > > > Well, I'm somewhat reluctant to stick network related code into mm/, it > > seems well separated now. > > What I had in mind was something like: > > +static DEFINE_SPINLOCK(memalloc_lock); > +static int memalloc_socks; > + > +atomic_t memalloc_skbs_used; > +EXPORT_SYMBOL_GPL(memalloc_skbs_used); > + > +int sk_adjust_memalloc(int nr_socks) > +{ > + unsigned long flags; > + unsigned int reserve; > + int err; > + > + spin_lock_irqsave(&memalloc_lock, flags); > + > + memalloc_socks += nr_socks; > + BUG_ON(memalloc_socks < 0); > + > + reserve = nr_socks * (2 * MAX_PHYS_SEGMENTS + /* outbound */ > + 5 * MAX_CONCURRENT_SKBS); /* inbound */ > + > + err = adjust_memalloc_reserve(reserve); > + spin_unlock_irqrestore(&memalloc_lock, flags); > + if (err) { > + printk(KERN_WARNING > + "Unable to change RX reserve to: %lu, error: %d\n", > + reserve, err); > + } > + return err; > +} > > The original code missed the brackets, so 5 * MAX_CONCURRENT_SKBS wasn't done > per socket. But the comment said it was per socket, so I added in this version. Ah right, I did that in v3, with a similar comment, but I realised that the inbound reserve need not be per socket, and that the comment was ambiguous enough to allow this reading. Why not per socket, its used to place an upper bound, its not calculating one, its setting one. Like you can see in memalloc_skbs_inc(), it limits to MAX_CONCURRENT_SKBS. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org