From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 80BF16B01F1 for ; Fri, 27 Aug 2010 01:00:43 -0400 (EDT) Received: by iwn33 with SMTP id 33so2952805iwn.14 for ; Thu, 26 Aug 2010 22:00:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1282867897-31201-1-git-send-email-yinghan@google.com> Date: Fri, 27 Aug 2010 14:00:41 +0900 Message-ID: Subject: Re: [PATCH] vmscan: fix missing place to check nr_swap_pages. From: Minchan Kim Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org To: Ying Han Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , KOSAKI Motohiro List-ID: On Fri, Aug 27, 2010 at 12:31 PM, Ying Han wrote: > On Thu, Aug 26, 2010 at 6:03 PM, Minchan Kim wrote: >> >> Hello. >> >> On Fri, Aug 27, 2010 at 9:11 AM, Ying Han wrote: >> > Fix a missed place where checks nr_swap_pages to do shrink_active_list. Make the >> > change that moves the check to common function inactive_anon_is_low. >> > >> >> Hmm.. AFAIR, we discussed it at that time but we concluded it's not good. >> That's because nr_swap_pages < 0 means both "NO SWAP" and "NOT enough >> swap space now". If we have a swap device or file but not enough space >> now, we need to aging anon pages to make inactive list enough size. >> Otherwise, working set pages would be swapped out more fast before >> promotion. > > We found the problem on one of our workloads where more TLB flush > happens without the change. Kswapd seems to be calling > shrink_active_list() which eventually clears access bit of those ptes > and does TLB flush > with ptep_clear_flush_young(). This system does not have swap > configured, and why aging the anon lru in that > case? True. I also wanted it but we have to care swap configured but non-enabling still yet system as well as non-swap configured system at that time. If your system is no swap configured, how about this? (It's a not formal proper patch but just quick patch to show the concept). diff --git a/mm/vmscan.c b/mm/vmscan.c index 3109ff7..641c6a6 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1580,6 +1580,11 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, spin_unlock_irq(&zone->lru_lock); } +/* + * If system doesn't have a swap configuration, + * it doesn't need to age anon pages in kswapd. + */ +#ifdef CONFIG_SWAP static int inactive_anon_is_low_global(struct zone *zone) { unsigned long active, inactive; @@ -1611,6 +1616,12 @@ static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); return low; } +#else +static inline int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) +{ + return 0; +} +#endif static int inactive_file_is_low_global(struct zone *zone) { -- Kind regards, Minchan Kim -- 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