From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 20 Mar 2001 09:13:42 -0800 (PST) From: Linus Torvalds Subject: Re: 3rd version of R/W mmap_sem patch available In-Reply-To: <20010320173349.A4839@fred.local> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: Andrew Morton , linux-mm@kvack.org List-ID: On Tue, 20 Mar 2001, Andi Kleen wrote: > > > > I don't think it's worth it. We should have basically zero contention on > > this lock now, and adding complexity to try to release it sounds like a > > bad idea when the only way to make contention on it is (a) kswapd (only > > when paging stuff out) and (b) multiple threads (only when taking > > concurrent page faults). > > Isn't (b) a rather common case in multi threaded applications ? Not if you're performance-sensitive, I bet. If you take so many pagefaults that the page_table_lock ends up being a problem, you have _more_ problems than that. We'll see. I will certainly re-consider if it ends up being shown to be a real problem. spinlock contention tends to be very easy to see on kernel profiles, especially the way they're done on Linux/x86 (inline - so you see evrey contention place separately). Linus -- 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.eu.org/Linux-MM/