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Tue, 10 Nov 2020 01:09:22 -0500 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4675C0613CF for ; Mon, 9 Nov 2020 22:09:22 -0800 (PST) Received: by mail-pf1-x442.google.com with SMTP id q10so10445351pfn.0 for ; Mon, 09 Nov 2020 22:09:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SM5QR02hbZk/xaCTMJcp/DAZns2BuDG/VMmjUxOQnWU=; b=or3XJ9irf/D9pLz3fmUfkf6iDsI41klsWua0T4eVg+pl/s9H17mEFtxwZX3CqavMcb x/AsrZRo8ff4N6XfCHmadYXh7EKkSL72aNZo46LPNzkHupSoVGXxaCRfFiyyDcx+o11f N3Xp+hHmmAA4YpId9kEYScxhWuCm53e7axUhvKkMzSmi2Nenb71cugVb1kJpIGDJckue lnvit3Y/sxqSoQlEn7GUzvZZ1s0eT6j5/esHeb9YnbQuoVdMVr95o9Oj8Alj6ewDq6dN 0lYR6d+Qnu1EyRRq467vLy6CQg4w1J7sxLAJnSts7oC15Eix+/xPu4AoTJPNdP3Wqlx8 C09g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SM5QR02hbZk/xaCTMJcp/DAZns2BuDG/VMmjUxOQnWU=; b=SM0nzuevfohO+VTDO/gkkW+WDvPd+u/NFhsPLSuLvsM22xQX0KCu5smIPsFPZX78IV 6vngozWHT9qhLTXOg+y/csMatof+x5UtzyaVwDI/U5c7Bl676488ByBLUeUD/X1SXRIq XGrc/AXNYyf4Vau8qKSQ/97vOg4/YssHZVbYVwBv1igb9gGum0Z5a0WgF40ygxXdvozt 5bxXLo7z+jO13TGnP+1tWoPhlFC2IjU10zD14hRxglslK9il7lqEH+d8M/iS0FCFFPyE 72WKHcjdZ48BS+PvKZgymTivTqhJbexKcmlFrfYZDJO/XChqb8PCmDCZz8VCcFGZ1VHx mQKw== X-Gm-Message-State: AOAM530pF4aOl1dqpXKWmilR+JygmsV+iYq5137GpaALe6DXrcK+VLVc UOhVedAEHHPf5u/qEwoNo8ySz67elpsjiA8zRAAn8g== X-Google-Smtp-Source: ABdhPJztVc92P0ds3eW6s5NmrcOMvO3xmXF5QmbTlVF7sojm3E9vLCb4vcMMlPrGJucdNDpDgQFVh77MpbkbuBk9lDk= X-Received: by 2002:a63:5804:: with SMTP id m4mr15486408pgb.31.1604988562263; Mon, 09 Nov 2020 22:09:22 -0800 (PST) MIME-Version: 1.0 References: <20201110054250.GA2906@localhost.localdomain> In-Reply-To: <20201110054250.GA2906@localhost.localdomain> From: Muchun Song Date: Tue, 10 Nov 2020 14:08:46 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v3 05/21] mm/hugetlb: Introduce pgtable allocation/freeing helpers To: Oscar Salvador Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Nov 10, 2020 at 1:42 PM Oscar Salvador wrote: > > On Tue, Nov 10, 2020 at 11:49:27AM +0800, Muchun Song wrote: > > On Tue, Nov 10, 2020 at 1:21 AM Oscar Salvador wrote: > > > > > > On Sun, Nov 08, 2020 at 10:10:57PM +0800, Muchun Song wrote: > > > > +static inline unsigned int pgtable_pages_to_prealloc_per_hpage(struct hstate *h) > > > > +{ > > > > + unsigned long vmemmap_size = vmemmap_pages_size_per_hpage(h); > > > > + > > > > + /* > > > > + * No need pre-allocate page tabels when there is no vmemmap pages > > > > + * to free. > > > s /tabels/tables/ > > > > Thanks. > > > > > > > > > +static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page) > > > > +{ > > > > + int i; > > > > + pgtable_t pgtable; > > > > + unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h); > > > > + > > > > + if (!nr) > > > > + return 0; > > > > + > > > > + vmemmap_pgtable_init(page); > > > > + > > > > + for (i = 0; i < nr; i++) { > > > > + pte_t *pte_p; > > > > + > > > > + pte_p = pte_alloc_one_kernel(&init_mm); > > > > + if (!pte_p) > > > > + goto out; > > > > + vmemmap_pgtable_deposit(page, virt_to_page(pte_p)); > > > > + } > > > > + > > > > + return 0; > > > > +out: > > > > + while (i-- && (pgtable = vmemmap_pgtable_withdraw(page))) > > > > + pte_free_kernel(&init_mm, page_to_virt(pgtable)); > > > > > > would not be enough to: > > > > > > while (pgtable = vmemmap_pgtable_withdrag(page)) > > > pte_free_kernel(&init_mm, page_to_virt(pgtable)); > > > > The vmemmap_pgtable_withdraw can not return NULL. So we can not > > drop the "i--". > > Yeah, you are right, I managed to confuse myself. > But why not make it return null, something like: > > static pgtable_t vmemmap_pgtable_withdraw(struct page *page) > { > pgtable_t pgtable; > > /* FIFO */ > pgtable = page_huge_pte(page); The check should be added here. if (!pgtable) return NULL; Just like my previous v2 patch does. In this case, we can drop those checks. What do you think? > page_huge_pte(page) = list_first_entry_or_null(&pgtable->lru, > struct page, lru); > if (page_huge_pte(page)) > list_del(&pgtable->lru); > > return page_huge_pte(page) ? pgtable : NULL; > } > > What do you think? > > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun