From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id 5CA1C6B0254 for ; Wed, 29 Jul 2015 08:25:18 -0400 (EDT) Received: by wicgb10 with SMTP id gb10so198138084wic.1 for ; Wed, 29 Jul 2015 05:25:17 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o3si26750628wic.109.2015.07.29.05.25.16 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 29 Jul 2015 05:25:16 -0700 (PDT) Subject: Re: [PATCH 10/10] mm, page_alloc: Only enforce watermarks for order-0 allocations References: <1437379219-9160-1-git-send-email-mgorman@suse.com> <1437379219-9160-11-git-send-email-mgorman@suse.com> From: Vlastimil Babka Message-ID: <55B8C629.80303@suse.cz> Date: Wed, 29 Jul 2015 14:25:13 +0200 MIME-Version: 1.0 In-Reply-To: <1437379219-9160-11-git-send-email-mgorman@suse.com> Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Linux-MM Cc: Johannes Weiner , Rik van Riel , Pintu Kumar , Xishi Qiu , Gioh Kim , LKML , Mel Gorman On 07/20/2015 10:00 AM, Mel Gorman wrote: [...] > static bool __zone_watermark_ok(struct zone *z, unsigned int order, > unsigned long mark, int classzone_idx, int alloc_flags, > @@ -2259,7 +2261,7 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order, > { > long min = mark; > int o; > - long free_cma = 0; > + const bool atomic = (alloc_flags & ALLOC_HARDER); > > /* free_pages may go negative - that's OK */ > free_pages -= (1 << order) - 1; > @@ -2271,7 +2273,7 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order, > * If the caller is not atomic then discount the reserves. This will > * over-estimate how the atomic reserve but it avoids a search > */ > - if (likely(!(alloc_flags & ALLOC_HARDER))) > + if (likely(!atomic)) > free_pages -= z->nr_reserved_highatomic; > else > min -= min / 4; > @@ -2279,22 +2281,30 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order, > #ifdef CONFIG_CMA > /* If allocation can't use CMA areas don't use free CMA pages */ > if (!(alloc_flags & ALLOC_CMA)) > - free_cma = zone_page_state(z, NR_FREE_CMA_PAGES); > + free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES); > #endif > > - if (free_pages - free_cma <= min + z->lowmem_reserve[classzone_idx]) > + if (free_pages <= min + z->lowmem_reserve[classzone_idx]) > return false; > - for (o = 0; o < order; o++) { > - /* At the next order, this order's pages become unavailable */ > - free_pages -= z->free_area[o].nr_free << o; > > - /* Require fewer higher order pages to be free */ > - min >>= 1; > + /* order-0 watermarks are ok */ > + if (!order) > + return true; > + > + /* Check at least one high-order page is free */ > + for (o = order; o < MAX_ORDER; o++) { > + struct free_area *area = &z->free_area[o]; > + int mt; > + > + if (atomic && area->nr_free) > + return true; This may be a false positive due to MIGRATE_CMA or MIGRATE_ISOLATE pages being the only free ones. But maybe it doesn't matter that much? > > - if (free_pages <= min) > - return false; > + for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) { > + if (!list_empty(&area->free_list[mt])) > + return true; > + } This may be a false negative for ALLOC_CMA allocations, if the only free pages are of MIGRATE_CMA. Arguably that's the worse case than a false positive? > } > - return true; > + return false; > } > > bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > -- 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