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 X-Spam-Level: X-Spam-Status: No, score=-8.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95118C4361B for ; Thu, 10 Dec 2020 15:58:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB7AF23D57 for ; Thu, 10 Dec 2020 15:58:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB7AF23D57 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 319226B0036; Thu, 10 Dec 2020 10:58:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2CAB46B005D; Thu, 10 Dec 2020 10:58:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1B93C6B0068; Thu, 10 Dec 2020 10:58:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0210.hostedemail.com [216.40.44.210]) by kanga.kvack.org (Postfix) with ESMTP id 06EFE6B0036 for ; Thu, 10 Dec 2020 10:58:00 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id BBD111EF2 for ; Thu, 10 Dec 2020 15:57:59 +0000 (UTC) X-FDA: 77577828678.16.title47_480169d273f9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id 9AE7E100E690B for ; Thu, 10 Dec 2020 15:57:59 +0000 (UTC) X-HE-Tag: title47_480169d273f9 X-Filterd-Recvd-Size: 8154 Received: from mail-pg1-f196.google.com (mail-pg1-f196.google.com [209.85.215.196]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Dec 2020 15:57:58 +0000 (UTC) Received: by mail-pg1-f196.google.com with SMTP id o5so4574957pgm.10 for ; Thu, 10 Dec 2020 07:57:58 -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=Fnon7sDzka34R7LgC0De8tPIdaalVEeRV2dY0iPqfl8=; b=GgNwNSHdatu+tNWPwIJEz9GCAzeb56lDlxA8kMpi4aHDozUFZ5Sv3Lw+uEOWSVGtjT wI1Zn7rPAUosJLJx34F3dHvx8+ImP9VzS/i2vOXMsaD5sXMwTDygmfDuZhPeTcj7N3Js q9zMVql+zspvvDxtgweapTbN1vy/kjQ3CVgAq2dP4x0Pnr2rKswaR+rvKlUNjFwFjKke s/gM3raMy1TMT/t+GDJj7x4RRZKOtqPMsX39apcdidkcGjXIj4EFwSauxx4/FB3vyDsv 4une5ur5AR6djKj+qUUGozr5Nfi2yvWNNUcR6tG4Xe5nRbhd+oZGFJK9H5aDHPqkcwJk hYrQ== 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=Fnon7sDzka34R7LgC0De8tPIdaalVEeRV2dY0iPqfl8=; b=KOi+yt1SRKAPQqEMbUPBUczDAOsoNbfzEgk+COBoH+RoVNBU5M48cPmISsd/KVx9a/ fpOgZNdJ7HYAGINLnC66orNhRfCAdYQEkl89i3fRyzCVEU/gbv92BYsWTNw7ZNlSB9Te 2Mj1rzGsLvaIx49ocDkLcZlJVX6wSOLDMuIBQvot0gvlawz1n4RjE3u2clXlkFpp6hxM dP5kov8vdfVhoK+KAqXXFoLSJjNdQHVa6di3eebGnZHMun8papVArdVVjZ9Ihpf4bPyX nNQ6g7OhlFp8otFE0T2jsq5EIbUD1OJh4b+E4cL/jnCsT3mmTSuKK7DDHL12xIArpEFb ahlA== X-Gm-Message-State: AOAM5322crDMnjyKXcnOQsv7fN5FtCdr4jZC/Qht+uWKjYMYUlhuug3w sawd5Ddxc6lwL+n3N8h+X9qcpTYb60GD1x3wnu6S0g== X-Google-Smtp-Source: ABdhPJzqiQKGJsmus7zKhdtqlGPdLVV43tunbznKDaEHRk/DlgkMGu/McZ++C6DuhMpQ2zRSMZzvRSssSYYMEE1rsgQ= X-Received: by 2002:a63:cd14:: with SMTP id i20mr7217766pgg.31.1607615877450; Thu, 10 Dec 2020 07:57:57 -0800 (PST) MIME-Version: 1.0 References: <20201210035526.38938-1-songmuchun@bytedance.com> <20201210035526.38938-5-songmuchun@bytedance.com> <20201210144256.GB8538@localhost.localdomain> In-Reply-To: <20201210144256.GB8538@localhost.localdomain> From: Muchun Song Date: Thu, 10 Dec 2020 23:57:21 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v8 04/12] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page 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 , "Song Bao Hua (Barry Song)" , David Hildenbrand , 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 Thu, Dec 10, 2020 at 10:43 PM Oscar Salvador wrote: > > On Thu, Dec 10, 2020 at 11:55:18AM +0800, Muchun Song wrote: > > The free_vmemmap_pages_per_hpage() which indicate that how many vmemmap > > pages associated with a HugeTLB page that can be freed to the buddy > > allocator just returns zero now, because all infrastructure is not > > ready. Once all the infrastructure is ready, we will rework this > > function to support the feature. > > I would reword the above to: > > "free_vmemmap_pages_per_hpage(), which indicates how many vmemmap > pages associated with a HugeTLB page can be freed, returns zero for > now, which means the feature is disabled. > We will enable it once all the infrastructure is there." Thanks for your suggestion. > > Or something along those lines. > > > Signed-off-by: Muchun Song > > Overall this looks good to me, and it has seen a considerable > simplification, which is good. > Some nits/questions below: > > > > +#define vmemmap_hpage_addr_end(addr, end) \ > > +({ \ > > + unsigned long __boundary; \ > > + __boundary = ((addr) + VMEMMAP_HPAGE_SIZE) & VMEMMAP_HPAGE_MASK; \ > > + (__boundary - 1 < (end) - 1) ? __boundary : (end); \ > > +}) > > Maybe add a little comment explaining what are you trying to get here. OK. Will do. > > > +/* > > + * Walk a vmemmap address to the pmd it maps. > > + */ > > +static pmd_t *vmemmap_to_pmd(unsigned long addr) > > +{ > > + pgd_t *pgd; > > + p4d_t *p4d; > > + pud_t *pud; > > + pmd_t *pmd; > > + > > + pgd = pgd_offset_k(addr); > > + if (pgd_none(*pgd)) > > + return NULL; > > + > > + p4d = p4d_offset(pgd, addr); > > + if (p4d_none(*p4d)) > > + return NULL; > > + > > + pud = pud_offset(p4d, addr); > > + if (pud_none(*pud)) > > + return NULL; > > + > > + pmd = pmd_offset(pud, addr); > > + if (pmd_none(*pmd)) > > + return NULL; > > + > > + return pmd; > > +} > > I saw that some people suggested to put all the non-hugetlb vmemmap > functions under sparsemem-vmemmap.c, which makes some sense if some > feature is going to re-use this code somehow. (I am not sure if the > recent patches that take advantage of this feature for ZONE_DEVICE needs > something like this). > > I do not have a strong opinion on this though. Yeah, I also thought about this. I prefer moving the common code to the sparsemem-vmemmap.c. If more people agree with this, I can do this in the next version. :) > > > +static void vmemmap_reuse_pte_range(struct page *reuse, pte_t *pte, > > + unsigned long start, unsigned long end, > > + struct list_head *vmemmap_pages) > > +{ > > + /* > > + * Make the tail pages are mapped with read-only to catch > > + * illegal write operation to the tail pages. > > + */ > > + pgprot_t pgprot = PAGE_KERNEL_RO; > > + pte_t entry = mk_pte(reuse, pgprot); > > + unsigned long addr; > > + > > + for (addr = start; addr < end; addr += PAGE_SIZE, pte++) { > > + struct page *page; > > + > > + VM_BUG_ON(pte_none(*pte)); > > If it is none, page will be NULL and we will crash in the list_add > below? Yeah, I think that here should be a BUG_ON. > > > +static void vmemmap_remap_range(unsigned long start, unsigned long end, > > + struct list_head *vmemmap_pages) > > +{ > > + pmd_t *pmd; > > + unsigned long next, addr = start; > > + struct page *reuse = NULL; > > + > > + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); > > + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); > > + VM_BUG_ON((start >> PUD_SHIFT) != (end >> PUD_SHIFT)); > This last VM_BUG_ON, is to see if both fall under the same PUD table? Right. > > > + > > + pmd = vmemmap_to_pmd(addr); > > + BUG_ON(!pmd); > > Which is the criteria you followed to make this BUG_ON and VM_BUG_ON > in the check from vmemmap_reuse_pte_range? Indeed, I am somewhat confused. Should be unified. I should use BUG_ON here and in vmemmap_reuse_pte_range. > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun