From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754478Ab2KUKWR (ORCPT ); Wed, 21 Nov 2012 05:22:17 -0500 Received: from cantor2.suse.de ([195.135.220.15]:43672 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754418Ab2KUKWO (ORCPT ); Wed, 21 Nov 2012 05:22:14 -0500 From: Mel Gorman To: Peter Zijlstra , Andrea Arcangeli , Ingo Molnar Cc: Rik van Riel , Johannes Weiner , Hugh Dickins , Thomas Gleixner , Paul Turner , Lee Schermerhorn , Alex Shi , Linus Torvalds , Andrew Morton , Linux-MM , LKML , Mel Gorman Subject: [PATCH 10/46] mm: compaction: Add scanned and isolated counters for compaction Date: Wed, 21 Nov 2012 10:21:16 +0000 Message-Id: <1353493312-8069-11-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.9.2 In-Reply-To: <1353493312-8069-1-git-send-email-mgorman@suse.de> References: <1353493312-8069-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Compaction already has tracepoints to count scanned and isolated pages but it requires that ftrace be enabled and if that information has to be written to disk then it can be disruptive. This patch adds vmstat counters for compaction called compact_migrate_scanned, compact_free_scanned and compact_isolated. With these counters, it is possible to define a basic cost model for compaction. This approximates of how much work compaction is doing and can be compared that with an oprofile showing TLB misses and see if the cost of compaction is being offset by THP for example. Minimally a compaction patch can be evaluated in terms of whether it increases or decreases cost. The basic cost model looks like this Fundamental unit u: a word sizeof(void *) Ca = cost of struct page access = sizeof(struct page) / u Cmc = Cost migrate page copy = (Ca + PAGE_SIZE/u) * 2 Cmf = Cost migrate failure = Ca * 2 Ci = Cost page isolation = (Ca + Wi) where Wi is a constant that should reflect the approximate cost of the locking operation. Csm = Cost migrate scanning = Ca Csf = Cost free scanning = Ca Overall cost = (Csm * compact_migrate_scanned) + (Csf * compact_free_scanned) + (Ci * compact_isolated) + (Cmc * pgmigrate_success) + (Cmf * pgmigrate_failed) Where the values are read from /proc/vmstat. This is very basic and ignores certain costs such as the allocation cost to do a migrate page copy but any improvement to the model would still use the same vmstat counters. Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel --- include/linux/vm_event_item.h | 2 ++ mm/compaction.c | 8 ++++++++ mm/vmstat.c | 3 +++ 3 files changed, 13 insertions(+) diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index 8aa7cb9..a1f750b 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -42,6 +42,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, PGMIGRATE_SUCCESS, PGMIGRATE_FAIL, #endif #ifdef CONFIG_COMPACTION + COMPACTMIGRATE_SCANNED, COMPACTFREE_SCANNED, + COMPACTISOLATED, COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS, #endif #ifdef CONFIG_HUGETLB_PAGE diff --git a/mm/compaction.c b/mm/compaction.c index 2c077a7..aee7443 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -356,6 +356,10 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, if (blockpfn == end_pfn) update_pageblock_skip(cc, valid_page, total_isolated, false); + count_vm_events(COMPACTFREE_SCANNED, nr_scanned); + if (total_isolated) + count_vm_events(COMPACTISOLATED, total_isolated); + return total_isolated; } @@ -646,6 +650,10 @@ next_pageblock: trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); + count_vm_events(COMPACTMIGRATE_SCANNED, nr_scanned); + if (nr_isolated) + count_vm_events(COMPACTISOLATED, nr_isolated); + return low_pfn; } diff --git a/mm/vmstat.c b/mm/vmstat.c index 89a7fd6..3a067fa 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -779,6 +779,9 @@ const char * const vmstat_text[] = { "pgmigrate_fail", #endif #ifdef CONFIG_COMPACTION + "compact_migrate_scanned", + "compact_free_scanned", + "compact_isolated", "compact_stall", "compact_fail", "compact_success", -- 1.7.9.2