From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751800AbdCANz3 (ORCPT ); Wed, 1 Mar 2017 08:55:29 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:38016 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751037AbdCANzX (ORCPT ); Wed, 1 Mar 2017 08:55:23 -0500 From: Johannes Weiner To: Andrew Morton Cc: Jia He , Michal Hocko , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 9/9] mm: remove unnecessary back-off function when retrying page reclaim Date: Tue, 28 Feb 2017 16:40:07 -0500 Message-Id: <20170228214007.5621-10-hannes@cmpxchg.org> X-Mailer: git-send-email 2.11.1 In-Reply-To: <20170228214007.5621-1-hannes@cmpxchg.org> References: <20170228214007.5621-1-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The backoff mechanism is not needed. If we have MAX_RECLAIM_RETRIES loops without progress, we'll OOM anyway; backing off might cut one or two iterations off that in the rare OOM case. If we have intermittent success reclaiming a few pages, the backoff function gets reset also, and so is of little help in these scenarios. We might want a backoff function for when there IS progress, but not enough to be satisfactory. But this isn't that. Remove it. Signed-off-by: Johannes Weiner --- mm/page_alloc.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9ac639864bed..223644afed28 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3511,11 +3511,10 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) /* * Checks whether it makes sense to retry the reclaim to make a forward progress * for the given allocation request. - * The reclaim feedback represented by did_some_progress (any progress during - * the last reclaim round) and no_progress_loops (number of reclaim rounds without - * any progress in a row) is considered as well as the reclaimable pages on the - * applicable zone list (with a backoff mechanism which is a function of - * no_progress_loops). + * + * We give up when we either have tried MAX_RECLAIM_RETRIES in a row + * without success, or when we couldn't even meet the watermark if we + * reclaimed all remaining pages on the LRU lists. * * Returns true if a retry is viable or false to enter the oom path. */ @@ -3560,13 +3559,11 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order, bool wmark; available = reclaimable = zone_reclaimable_pages(zone); - available -= DIV_ROUND_UP((*no_progress_loops) * available, - MAX_RECLAIM_RETRIES); available += zone_page_state_snapshot(zone, NR_FREE_PAGES); /* - * Would the allocation succeed if we reclaimed the whole - * available? + * Would the allocation succeed if we reclaimed all + * reclaimable pages? */ wmark = __zone_watermark_ok(zone, order, min_wmark, ac_classzone_idx(ac), alloc_flags, available); -- 2.11.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id BB7B36B0392 for ; Tue, 28 Feb 2017 16:46:34 -0500 (EST) Received: by mail-wr0-f197.google.com with SMTP id q39so9391434wrb.3 for ; Tue, 28 Feb 2017 13:46:34 -0800 (PST) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id z23si4006859wrb.20.2017.02.28.13.46.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Feb 2017 13:46:33 -0800 (PST) From: Johannes Weiner Subject: [PATCH 9/9] mm: remove unnecessary back-off function when retrying page reclaim Date: Tue, 28 Feb 2017 16:40:07 -0500 Message-Id: <20170228214007.5621-10-hannes@cmpxchg.org> In-Reply-To: <20170228214007.5621-1-hannes@cmpxchg.org> References: <20170228214007.5621-1-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Jia He , Michal Hocko , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com The backoff mechanism is not needed. If we have MAX_RECLAIM_RETRIES loops without progress, we'll OOM anyway; backing off might cut one or two iterations off that in the rare OOM case. If we have intermittent success reclaiming a few pages, the backoff function gets reset also, and so is of little help in these scenarios. We might want a backoff function for when there IS progress, but not enough to be satisfactory. But this isn't that. Remove it. Signed-off-by: Johannes Weiner --- mm/page_alloc.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9ac639864bed..223644afed28 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3511,11 +3511,10 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) /* * Checks whether it makes sense to retry the reclaim to make a forward progress * for the given allocation request. - * The reclaim feedback represented by did_some_progress (any progress during - * the last reclaim round) and no_progress_loops (number of reclaim rounds without - * any progress in a row) is considered as well as the reclaimable pages on the - * applicable zone list (with a backoff mechanism which is a function of - * no_progress_loops). + * + * We give up when we either have tried MAX_RECLAIM_RETRIES in a row + * without success, or when we couldn't even meet the watermark if we + * reclaimed all remaining pages on the LRU lists. * * Returns true if a retry is viable or false to enter the oom path. */ @@ -3560,13 +3559,11 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order, bool wmark; available = reclaimable = zone_reclaimable_pages(zone); - available -= DIV_ROUND_UP((*no_progress_loops) * available, - MAX_RECLAIM_RETRIES); available += zone_page_state_snapshot(zone, NR_FREE_PAGES); /* - * Would the allocation succeed if we reclaimed the whole - * available? + * Would the allocation succeed if we reclaimed all + * reclaimable pages? */ wmark = __zone_watermark_ok(zone, order, min_wmark, ac_classzone_idx(ac), alloc_flags, available); -- 2.11.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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