From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 22 Nov 2004 14:13:06 -0800 (PST) From: Christoph Lameter Subject: Re: deferred rss update instead of sloppy rss In-Reply-To: <20041122141148.1e6ef125.akpm@osdl.org> Message-ID: References: <20041122141148.1e6ef125.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: hugh@veritas.com, torvalds@osdl.org, benh@kernel.crashing.org, nickpiggin@yahoo.com.au, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: On Mon, 22 Nov 2004, Andrew Morton wrote: > hrm. I cannot see anywhere in this patch where you update task_struct.rss. This is just the piece around it dealing with rss. The updating of rss happens in the generic code. The change to that is trivial. I can repost the whole shebang if you want. > > + /* only holding mmap_sem here maybe get page_table_lock too? */ > > + mm->rss += tsk->rss; > > + tsk->rss = 0; > > up_read(&mm->mmap_sem); > > mmap_sem needs to be held for writing, surely? If there are no page faults occurring anymore then we would not need to get the lock. Q: Is it safe to assume that no faults occur anymore at this point? > just to prevent transient gross inaccuracies. For some value of "16". The page fault code only increments rss. For larger transactions that increase / decrease rss significantly the page_table_lock is taken and mm->rss is updated directly. So no gross inaccuracies can result. -- 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: aart@kvack.org