From nobody Tue Sep 16 00:50:12 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE970C678DB for ; Mon, 9 Jan 2023 15:19:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237316AbjAIPSy (ORCPT ); Mon, 9 Jan 2023 10:18:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237181AbjAIPRz (ORCPT ); Mon, 9 Jan 2023 10:17:55 -0500 Received: from outbound-smtp39.blacknight.com (outbound-smtp39.blacknight.com [46.22.139.222]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D074D32E for ; Mon, 9 Jan 2023 07:17:26 -0800 (PST) Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp39.blacknight.com (Postfix) with ESMTPS id 775D71FB2 for ; Mon, 9 Jan 2023 15:17:25 +0000 (GMT) Received: (qmail 18139 invoked from network); 9 Jan 2023 15:17:25 -0000 Received: from unknown (HELO morpheus.112glenside.lan) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPA; 9 Jan 2023 15:17:25 -0000 From: Mel Gorman To: Linux-MM Cc: Andrew Morton , Michal Hocko , NeilBrown , Thierry Reding , Matthew Wilcox , Vlastimil Babka , LKML , Mel Gorman Subject: [PATCH 4/7] mm/page_alloc: Explicitly define what alloc flags deplete min reserves Date: Mon, 9 Jan 2023 15:16:28 +0000 Message-Id: <20230109151631.24923-5-mgorman@techsingularity.net> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230109151631.24923-1-mgorman@techsingularity.net> References: <20230109151631.24923-1-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" As there are more ALLOC_ flags that affect reserves, define what flags affect reserves and clarify the effect of each flag. Signed-off-by: Mel Gorman Acked-by: Michal Hocko Acked-by: Vlastimil Babka --- mm/internal.h | 3 +++ mm/page_alloc.c | 34 ++++++++++++++++++++++------------ 2 files changed, 25 insertions(+), 12 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 178484d9fd94..8706d46863df 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -749,6 +749,9 @@ unsigned int reclaim_clean_pages_from_list(struct zone = *zone, #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAI= M set */ =20 +/* Flags that allow allocations below the min watermark. */ +#define ALLOC_RESERVES (ALLOC_HARDER|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|AL= LOC_OOM) + enum ttu_flags; struct tlbflush_unmap_batch; =20 diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0ef4f3236a5a..6f41b84a97ac 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3949,15 +3949,14 @@ ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE); static inline long __zone_watermark_unusable_free(struct zone *z, unsigned int order, unsigned int alloc_flags) { - const bool alloc_harder =3D (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); long unusable_free =3D (1 << order) - 1; =20 /* - * If the caller does not have rights to ALLOC_HARDER then subtract - * the high-atomic reserves. This will over-estimate the size of the - * atomic reserve but it avoids a search. + * If the caller does not have rights to reserves below the min + * watermark then subtract the high-atomic reserves. This will + * over-estimate the size of the atomic reserve but it avoids a search. */ - if (likely(!alloc_harder)) + if (likely(!(alloc_flags & ALLOC_RESERVES))) unusable_free +=3D z->nr_reserved_highatomic; =20 #ifdef CONFIG_CMA @@ -3981,25 +3980,36 @@ bool __zone_watermark_ok(struct zone *z, unsigned i= nt order, unsigned long mark, { long min =3D mark; int o; - const bool alloc_harder =3D (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); =20 /* free_pages may go negative - that's OK */ free_pages -=3D __zone_watermark_unusable_free(z, order, alloc_flags); =20 - if (alloc_flags & ALLOC_MIN_RESERVE) - min -=3D min / 2; + if (unlikely(alloc_flags & ALLOC_RESERVES)) { + /* + * __GFP_HIGH allows access to 50% of the min reserve as well + * as OOM. + */ + if (alloc_flags & ALLOC_MIN_RESERVE) + min -=3D min / 2; =20 - if (unlikely(alloc_harder)) { /* - * OOM victims can try even harder than normal ALLOC_HARDER + * Non-blocking allocations can access some of the reserve + * with more access if also __GFP_HIGH. The reasoning is that + * a non-blocking caller may incur a more severe penalty + * if it cannot get memory quickly, particularly if it's + * also __GFP_HIGH. + */ + if (alloc_flags & ALLOC_HARDER) + min -=3D min / 4; + + /* + * OOM victims can try even harder than the normal reserve * users on the grounds that it's definitely going to be in * the exit path shortly and free memory. Any allocation it * makes during the free path will be small and short-lived. */ if (alloc_flags & ALLOC_OOM) min -=3D min / 2; - else - min -=3D min / 4; } =20 /* --=20 2.35.3