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Shutemov" , Matthew Wilcox , Andrew Morton , Linux MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1654822355; a=rsa-sha256; cv=none; b=yagcdnXSOzcVw7cHmjN1VZC0BDXr7eaYe1MiyNDp7w7viPR1qGZvXT7kiCbSJdz/DbmD5Q wIWXWjF8dhkt2O2yLSK6s6eSSNx4hpp28BiMYtm6P9UeYjnvlAZik1ki51a49mv4pAH22r Jcf2Coq/lGm1bYfPZdATw+j1WYkfbWk= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ZTkYPqSJ; spf=pass (imf14.hostedemail.com: domain of zokeefe@google.com designates 209.85.208.172 as permitted sender) smtp.mailfrom=zokeefe@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1654822355; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ZWMVPV3EDKgxuFoSQmmIWIuS1uTwoXL+jJbB94OiqI0=; b=ybcIAzmH9vn0p7+TmGz79ObDopoUFCtXLSU7Sn2pAuPH+QJpUOqHANkEWXY1WmgNSCIikg PQQ2o40CQ0US5AdznzhWLZYj1wLQFUB30xTq72romdYoW0J8aqwy2ID7V3fOb7SSPwqfUn S0nUDl4jD7KK9wSnKtl8f02JA+NnNYM= X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 023A2100059 X-Rspam-User: Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ZTkYPqSJ; spf=pass (imf14.hostedemail.com: domain of zokeefe@google.com designates 209.85.208.172 as permitted sender) smtp.mailfrom=zokeefe@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: fbz49mjzqqesu1j779hrtmg1ryne1kd1 X-HE-Tag: 1654822354-302228 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, Jun 9, 2022 at 5:08 PM Yang Shi wrote: > > On Thu, Jun 9, 2022 at 3:21 PM Zach O'Keefe wrote: > > > > On Mon, Jun 6, 2022 at 2:44 PM Yang Shi wrote: > > > > > > There are couple of places that check whether the vma size is ok for > > > THP or not, they are open coded and duplicate, introduce > > > transhuge_vma_size_ok() helper to do the job. > > > > > > Signed-off-by: Yang Shi > > > --- > > > include/linux/huge_mm.h | 17 +++++++++++++++++ > > > mm/huge_memory.c | 5 +---- > > > mm/khugepaged.c | 12 ++++++------ > > > 3 files changed, 24 insertions(+), 10 deletions(-) > > > > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > > index 648cb3ce7099..a8f61db47f2a 100644 > > > --- a/include/linux/huge_mm.h > > > +++ b/include/linux/huge_mm.h > > > @@ -116,6 +116,18 @@ extern struct kobj_attribute shmem_enabled_attr; > > > > > > extern unsigned long transparent_hugepage_flags; > > > > > > +/* > > > + * The vma size has to be large enough to hold an aligned HPAGE_PMD_SIZE area. > > > + */ > > > +static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma) > > > +{ > > > + if (round_up(vma->vm_start, HPAGE_PMD_SIZE) < > > > + (vma->vm_end & HPAGE_PMD_MASK)) > > > + return true; > > > + > > > + return false; > > > +} > > > > First time coming across round_up() - thanks for that - but for > > symmetry, maybe also use round_down() for the end? No strong opinion - > > just a suggestion given I've just discovered it. > > Yeah, round_down is fine too. > > > > > > static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, > > > unsigned long addr) > > > { > > > @@ -345,6 +357,11 @@ static inline bool transparent_hugepage_active(struct vm_area_struct *vma) > > > return false; > > > } > > > > > > +static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma) > > > +{ > > > + return false; > > > +} > > > + > > > static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, > > > unsigned long addr) > > > { > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > index 48182c8fe151..36ada544e494 100644 > > > --- a/mm/huge_memory.c > > > +++ b/mm/huge_memory.c > > > @@ -71,10 +71,7 @@ unsigned long huge_zero_pfn __read_mostly = ~0UL; > > > > > > bool transparent_hugepage_active(struct vm_area_struct *vma) > > > { > > > - /* The addr is used to check if the vma size fits */ > > > - unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; > > > - > > > - if (!transhuge_vma_suitable(vma, addr)) > > > + if (!transhuge_vma_size_ok(vma)) > > > return false; > > > if (vma_is_anonymous(vma)) > > > return __transparent_hugepage_enabled(vma); > > > > Do we need a check for vma->vm_pgoff alignment here, after > > !vma_is_anonymous(), and now that we don't call > > transhuge_vma_suitable()? > > Actually I was thinking about this too. But the THPeligible bit shown > by smaps is a little bit ambiguous for file vma. The document says: > "THPeligible" indicates whether the mapping is eligible for allocating > THP pages - 1 if true, 0 otherwise. > > Even though it doesn't fulfill the alignment, it is still possible to > get THP allocated, but just can't be PMD mapped. So the old behavior > of THPeligible for file vma seems problematic, or at least doesn't > match the document. I think the term "THP" is used ambiguously. Often, but not always, in the code, folks will go out of their way to specify "hugepage-sized" page vs "pmd-mapped hugepage" - but at least from my experience, external documentation doesn't. Given that THP as a concept doesn't make much sense without the possibility of pmd-mapping, I think "THPeligible here means "pmd mappable". For example, AnonHugePages in smaps means pmd-mapped anon hugepages. That all said - the following patches will delete transparent_hugepage_active() anyways. > I should elaborate this in the commit log. > > > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > > index 84b9cf4b9be9..d0f8020164fc 100644 > > > --- a/mm/khugepaged.c > > > +++ b/mm/khugepaged.c > > > @@ -454,6 +454,9 @@ bool hugepage_vma_check(struct vm_area_struct *vma, > > > vma->vm_pgoff, HPAGE_PMD_NR)) > > > return false; > > > > > > + if (!transhuge_vma_size_ok(vma)) > > > + return false; > > > + > > > /* Enabled via shmem mount options or sysfs settings. */ > > > if (shmem_file(vma->vm_file)) > > > return shmem_huge_enabled(vma); > > > @@ -512,9 +515,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma, > > > unsigned long vm_flags) > > > { > > > if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) && > > > - khugepaged_enabled() && > > > - (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) < > > > - (vma->vm_end & HPAGE_PMD_MASK))) { > > > + khugepaged_enabled()) { > > > if (hugepage_vma_check(vma, vm_flags)) > > > __khugepaged_enter(vma->vm_mm); > > > } > > > @@ -2142,10 +2143,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, > > > progress++; > > > continue; > > > } > > > - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; > > > + > > > + hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE); > > > hend = vma->vm_end & HPAGE_PMD_MASK; > > > - if (hstart >= hend) > > > - goto skip; > > > if (khugepaged_scan.address > hend) > > > goto skip; > > > if (khugepaged_scan.address < hstart) > > > > Likewise, could do round_down() here (just a suggestion) > > Fine to me. > > > > > > -- > > > 2.26.3 > > > > > >