From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 0C3686B0031 for ; Mon, 18 Nov 2013 15:49:51 -0500 (EST) Received: by mail-pa0-f45.google.com with SMTP id kp14so1485272pab.32 for ; Mon, 18 Nov 2013 12:49:51 -0800 (PST) Received: from psmtp.com ([74.125.245.193]) by mx.google.com with SMTP id hb3si10510458pac.268.2013.11.18.12.49.49 for ; Mon, 18 Nov 2013 12:49:50 -0800 (PST) Message-ID: <528A7D36.5020500@sr71.net> Date: Mon, 18 Nov 2013 12:48:54 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH] mm: call cond_resched() per MAX_ORDER_NR_PAGES pages copy References: <20131115225550.737E5C33@viggo.jf.intel.com> <20131115225553.B0E9DFFB@viggo.jf.intel.com> <1384800714-y653r3ch-mutt-n-horiguchi@ah.jp.nec.com> <1384800841-314l1f3e-mutt-n-horiguchi@ah.jp.nec.com> <528A6448.3080907@sr71.net> <1384806022-4718p9lh-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1384806022-4718p9lh-mutt-n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave.jiang@intel.com, akpm@linux-foundation.org, dhillf@gmail.com, Mel Gorman On 11/18/2013 12:20 PM, Naoya Horiguchi wrote: >> > Really, though, a lot of things seem to have MAX_ORDER set up so that >> > it's at 256MB or 512MB. That's an awful lot to do between rescheds. > Yes. > > BTW, I found that we have the same problem for other functions like > copy_user_gigantic_page, copy_user_huge_page, and maybe clear_gigantic_page. > So we had better handle them too. Is there a problem you're trying to solve here? The common case of the cond_resched() call boils down to a read of a percpu variable which will surely be in the L1 cache after the first run around the loop. In other words, it's about as cheap of an operation as we're going to get. Why bother trying to "optimize" it? -- 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