From mboxrd@z Thu Jan 1 00:00:00 1970 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 D9DEEC433F5 for ; Tue, 25 Jan 2022 16:44:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380625AbiAYQoh (ORCPT ); Tue, 25 Jan 2022 11:44:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1584500AbiAYQja (ORCPT ); Tue, 25 Jan 2022 11:39:30 -0500 Received: from mail-lj1-x22b.google.com (mail-lj1-x22b.google.com [IPv6:2a00:1450:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E75EC06173D for ; Tue, 25 Jan 2022 08:39:29 -0800 (PST) Received: by mail-lj1-x22b.google.com with SMTP id q22so8934631ljh.7 for ; Tue, 25 Jan 2022 08:39:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=FDpf/tqpMlV9Ib2LRvV4j3vhlXhSgAj3mSGN2d7ZcYY=; b=FbkCyN5KWevqIjBzepzV3zujCRXPPi2w+x9Sf9h+1yZiy/ezQGqJB/9ej79Rz2tHmQ cpySobBwvJqOilvtiU6wle2CgH+aBeeHmbLPiWaRsjPjnCXD8bRH20XKM6CtDAHBYSm3 IYukg5lNcTem467DaJZtbq1Ud8hhXDyp3BUJ1PHt3Xn/jk2Bw27IVxJLGYutUaBQgFjr yTwdpP/0yv3FR+qonYINVRoVCiTvLB55d9K/VtCiFg6nasKfhPviVUQ7lBfEQh4QRjpv wGFss31oaumvdnWDDHdh6I/x9fUPVTpBsqz1QP/o05RvFjcXxzUJtjVe5pvQU1wuenHf J+0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=FDpf/tqpMlV9Ib2LRvV4j3vhlXhSgAj3mSGN2d7ZcYY=; b=ycOnC9P1Idap8ALqXJeyhyMJVjxihBwngMcwn+ECnOmp1w4dOSo6FV8KJGq/28PbDt ArezFQQTTGQJpalKW6ad6wVIxqwCeSVD13Zo5+kjErbaoEwP77w9rtsSO6KNkaparzgV HD8bZ1h4+2RkqLttaixOOA/ao4x1WM+l8/prA1ihds5E3VdbCm58lQnFeegGFAJPbYov GRGWyj1AuAnGB8LXh8MEakgETJl3DmS3qlBwSl1VvbxA0dqT1vd4Xc//b3+CW6GYx50y ZFot/FC2QoJv/meYEGxLVTKQzsgFHgqQcFhmGc09rLouEOHRuslGUCBeHxGvxIDruTPi DxoQ== X-Gm-Message-State: AOAM532j9rput0D6GorjzXMdYaSmTQ2H8TqOIM2Y7mDRRmBXF/amaJg3 E3akU2XVI/wJg3O3igVT2nk= X-Google-Smtp-Source: ABdhPJwNxbGBBpe9r6A1WHWICesZo5SEMLzazCTOBWAPeAR7cp4CbLSQEB/IDzN4FGMhDmLs415Lrw== X-Received: by 2002:a2e:8815:: with SMTP id x21mr10229829ljh.392.1643128767612; Tue, 25 Jan 2022 08:39:27 -0800 (PST) Received: from pc638.lan ([155.137.26.201]) by smtp.gmail.com with ESMTPSA id h23sm333898lfv.46.2022.01.25.08.39.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Jan 2022 08:39:23 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: Andrew Morton Cc: linux-mm@kvack.org, LKML , Christoph Hellwig , Matthew Wilcox , Nicholas Piggin , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH v2 1/1] mm/vmalloc: Move draining areas out of caller context Date: Tue, 25 Jan 2022 17:39:12 +0100 Message-Id: <20220125163912.2809-1-urezki@gmail.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A caller initiates the drain procces from its context once the drain threshold is reached or passed. There are at least two drawbacks of doing so: a) a caller can be a high-prio or RT task. In that case it can stuck in doing the actual drain of all lazily freed areas. This is not optimal because such tasks usually are latency sensitive where the control should be returned back as soon as possible in order to drive such workloads in time. See 96e2db456135 ("mm/vmalloc: rework the drain logic") b) It is not safe to call vfree() during holding a spinlock due to the vmap_purge_lock mutex. The was a report about this from Zeal Robot here: https://lore.kernel.org/all/20211222081026.484058-1-chi.minghao@zte.com.cn Moving the drain to the separate work context addresses those issues. v1->v2: - Added prefix "_work" to the drain worker function. Signed-off-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index bdc7222f87d4..e5285c9d2e2a 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -793,6 +793,9 @@ RB_DECLARE_CALLBACKS_MAX(static, free_vmap_area_rb_augment_cb, static void purge_vmap_area_lazy(void); static BLOCKING_NOTIFIER_HEAD(vmap_notify_list); static unsigned long lazy_max_pages(void); +static void drain_vmap_area_work(struct work_struct *work); +static DECLARE_WORK(drain_vmap_work, drain_vmap_area_work); +static atomic_t drain_vmap_work_in_progress; static atomic_long_t nr_vmalloc_pages; @@ -1719,18 +1722,6 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) return true; } -/* - * Kick off a purge of the outstanding lazy areas. Don't bother if somebody - * is already purging. - */ -static void try_purge_vmap_area_lazy(void) -{ - if (mutex_trylock(&vmap_purge_lock)) { - __purge_vmap_area_lazy(ULONG_MAX, 0); - mutex_unlock(&vmap_purge_lock); - } -} - /* * Kick off a purge of the outstanding lazy areas. */ @@ -1742,6 +1733,23 @@ static void purge_vmap_area_lazy(void) mutex_unlock(&vmap_purge_lock); } +static void drain_vmap_area_work(struct work_struct *work) +{ + unsigned long nr_lazy; + + do { + mutex_lock(&vmap_purge_lock); + __purge_vmap_area_lazy(ULONG_MAX, 0); + mutex_unlock(&vmap_purge_lock); + + /* Recheck if further work is required. */ + nr_lazy = atomic_long_read(&vmap_lazy_nr); + } while (nr_lazy > lazy_max_pages()); + + /* We are done at this point. */ + atomic_set(&drain_vmap_work_in_progress, 0); +} + /* * Free a vmap area, caller ensuring that the area has been unmapped * and flush_cache_vunmap had been called for the correct range @@ -1768,7 +1776,8 @@ static void free_vmap_area_noflush(struct vmap_area *va) /* After this point, we may free va at any time */ if (unlikely(nr_lazy > lazy_max_pages())) - try_purge_vmap_area_lazy(); + if (!atomic_xchg(&drain_vmap_work_in_progress, 1)) + schedule_work(&drain_vmap_work); } /* -- 2.30.2