From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 6 Jan 2006 23:00:29 -0200 From: Marcelo Tosatti Subject: Re: [PATCH] use local_t for page statistics Message-ID: <20060107010029.GA5087@dmt.cnet> References: <20060106215332.GH8979@kvack.org> <20060106163313.38c08e37.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060106163313.38c08e37.akpm@osdl.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Benjamin LaHaise , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Nick Piggin List-ID: On Fri, Jan 06, 2006 at 04:33:13PM -0800, Andrew Morton wrote: > Benjamin LaHaise wrote: > > > > The patch below converts the mm page_states counters to use local_t. > > mod_page_state shows up in a few profiles on x86 and x86-64 due to the > > disable/enable interrupts operations touching the flags register. On > > both my laptop (Pentium M) and P4 test box this results in about 10 > > additional /bin/bash -c exit 0 executions per second (P4 went from ~759/s > > to ~771/s). Tested on x86 and x86-64. Oh, also add a pgcow statistic > > for the number of COW page faults. > > Bah. I think this is a better approach than the just-merged > mm-page_state-opt.patch, so I should revert that patch first? Don't think so - local_t operations are performed atomically, which is not required for most hotpath page statistics operations since proper locks are already held. What is wanted for these cases are simple inc/dec (non-atomic) instructions, which is what Nick's patch does by introducing __mod_page_state. Ben, have you tested mm-page_state-opt.patch? It should get rid of most "flags" save/restore on stack. -- 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