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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=zdSQFTCy7+/L4zU3ZF97r7YPRToNp4hA6tkIQzGJXC4=; b=FUGhwXUQFXzWGAfUoasROkqk8ySkZrziSKhpm7lqQnoNEXA1v0i2tdpBmPCjGEstyj At7bXAY5MNI/8l4QRnbQEB5Nvpwcvq5a7FDLvWe9JJjQ3/HAxJhQ00ewn4DNJ2hFuNAn QIGVrGTp3CXRagI49yEiysuRW6uDvK7nBmFaINHDK8EgwmpI5Jzj6ni1kXanjon/YFRY d2ss+nc9qOYBE7xO5SyDmSJFTvpnHGYKhkOly33eOEWsm+5RFKAET55WkdLQ1digNuaE XA1W7qQnO1ufCPEsWw0+Hz3sv1syAnUd5UGIz8z9ord9djqqhmMmsMVlBo9pqR5It12D 3cVg== X-Gm-Message-State: AOAM5315BiuPKtgBD4LAwDUoomz11fjf3hVKPQt4E+/mvvuAPYHhDLdj kw35HZuTJFBoMlXyhi0U1juQP45EWnpGmRDaAdvVOw== X-Google-Smtp-Source: ABdhPJxY3cmAN4MQVkEwrkoDndbn+RE6xEypaDMyAAT/Ov5wENT8YyEsfl1X4Gz4eLu7JEuIJjkGpp2htO2uZlxHZAM= X-Received: by 2002:a63:5804:: with SMTP id m4mr15125994pgb.31.1604980203620; Mon, 09 Nov 2020 19:50:03 -0800 (PST) MIME-Version: 1.0 References: <20201108141113.65450-1-songmuchun@bytedance.com> <20201108141113.65450-6-songmuchun@bytedance.com> <20201109172144.GB17356@linux> In-Reply-To: <20201109172144.GB17356@linux> From: Muchun Song Date: Tue, 10 Nov 2020 11:49:27 +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" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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--". > > > + return -ENOMEM; > > +} > > + > > +static void vmemmap_pgtable_free(struct hstate *h, struct page *page) > > +{ > > + pgtable_t pgtable; > > + unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h); > > + > > + if (!nr) > > + return; > > We can get rid of "nr" and its check and keep only the check below, right? Great, the check can go away. > AFAICS, they go together, e.g: if page_huge_pte does not return null, > it means that we preallocated a pagetable, and viceversa. > > > > + > > + pgtable = page_huge_pte(page); > > + if (!pgtable) > > + return; > > + > > + while (nr-- && (pgtable = vmemmap_pgtable_withdraw(page))) > > + pte_free_kernel(&init_mm, page_to_virt(pgtable)); > > Same as above, that "nr" can go? Here "nr" can not go. Because the vmemmap_pgtable_withdraw can not return NULL. Thanks. > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun