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rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v4 34/36] rmap: add folio_add_file_rmap_range() Content-Language: en-US To: "Yin, Fengwei" , "Matthew Wilcox (Oracle)" , linux-arch@vger.kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230315051444.3229621-1-willy@infradead.org> <20230315051444.3229621-35-willy@infradead.org> <387dc921-de2b-f244-985c-d1e6336d5909@arm.com> <01071d9c-483f-2d95-87a6-e1030acaf8dd@arm.com> <0f581d0d-3139-4007-2161-592a0a545b50@intel.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 569681C001A X-Stat-Signature: 1sdbsujd488kpurxyg41cmhs1inxw8oh X-HE-Tag: 1679057204-611310 X-HE-Meta: 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 KAHXBXH4 DqtUhJa3Y1PtfnW45pBGxXxbZrzndCsbM1onZI+6PiC7qzDmSAwcMahOGbmKXHOjbCZIxxrqA3tJpIxfkZpxoOSGncWHa+V8DAxTlNvNcEW51HuGj3mIYgsJN5HLyBAdUC3hJOB2ZAR9iulfRf6f76dsa7eXVHtEitQvzaCTK5iI3HpuBpmDfQtxJRCrBtHtI64KzBsc0+a3+/jxPxrIY116Prw== 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 17/03/2023 08:23, Yin, Fengwei wrote: [...] >>>>> FYI, I'm seeing a perf regression of about 1% when compiling the kernel on >>>>> Ampere Altra (arm64) with this whole series on top of v6.3-rc1 (In a VM using >>>>> ext4 filesystem). Looks like instruction aborts are taking much longer and a >>>>> selection of syscalls are a bit slower. Still hunting down the root cause. Will >>>>> report once I have conclusive diagnosis. >>>> >>>> I'm sorry - I'm struggling to find the exact cause. But its spending over 2x the >>>> amount of time in the instruction abort handling code once patches 32-36 are >>>> included. Everything in the flame graph is just taking longer. Perhaps we are >>>> getting more instruction aborts somehow? I have the flamegraphs if anyone wants >>>> them - just shout and I'll email them separately. >>> Thanks a lot to Ryan for sharing the flamegraphs to me. I found the __do_fault() >>> is called with patch 32-36 while no __do_fault() just with first 31 patches. I >>> suspect the folio_add_file_rmap_range() missed some PTEs population. Please give >>> me few days to find the root cause and fix. Sorry for this. >> >> You're welcome. Give me a shout once you have a re-spin and I'll rerun the tests. > Could you please help to try following changes? Thanks in advance. > > diff --git a/mm/filemap.c b/mm/filemap.c > index 40be33b5ee46..137011320c68 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -3504,15 +3504,16 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, > if (!pte_none(vmf->pte[count])) > goto skip; > > - if (vmf->address == addr) > - ret = VM_FAULT_NOPAGE; > - > count++; > continue; > skip: > if (count) { > set_pte_range(vmf, folio, page, count, addr); > folio_ref_add(folio, count); > + if ((vmf->address < (addr + count * PAGE_SIZE)) && > + (vmf->address >= addr)) > + ret = VM_FAULT_NOPAGE; > + > } > > count++; > @@ -3525,6 +3526,9 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, > if (count) { > set_pte_range(vmf, folio, page, count, addr); > folio_ref_add(folio, count); > + if ((vmf->address < (addr + count * PAGE_SIZE)) && > + (vmf->address >= addr)) > + ret = VM_FAULT_NOPAGE; > } > > vmf->pte = old_ptep; > I'm afraid this hasn't fixed it, and I still see __do_fault(). I'll send the flame graph over separately. Given I'm running on ext4, I wasn't expecting to see any large page cache folios? So I don't think we would have expected this patch to help anyway? (or perhaps there are still THP folios? But I think they will get PMD mapped?). > > Regards > Yin, Fengwei > >> >>> >>> >>> Regards >>> Yin, Fengwei >>> >>>> >>>>> >>>>> Thanks, >>>>> Ryan >>>>> >>>>> >>>>>> + } >>>>>> + >>>>>> + if (first) >>>>>> + nr++; >>>>>> + } while (page++, --nr_pages > 0); >>>>>> } else if (folio_test_pmd_mappable(folio)) { >>>>>> /* That test is redundant: it's for safety or to optimize out */ >>>>>> >>>>>> @@ -1354,6 +1362,30 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, >>>>>> mlock_vma_folio(folio, vma, compound); >>>>>> } >>>>>> >>>>>> +/** >>>>>> + * page_add_file_rmap - add pte mapping to a file page >>>>>> + * @page: the page to add the mapping to >>>>>> + * @vma: the vm area in which the mapping is added >>>>>> + * @compound: charge the page as compound or small page >>>>>> + * >>>>>> + * The caller needs to hold the pte lock. >>>>>> + */ >>>>>> +void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, >>>>>> + bool compound) >>>>>> +{ >>>>>> + struct folio *folio = page_folio(page); >>>>>> + unsigned int nr_pages; >>>>>> + >>>>>> + VM_WARN_ON_ONCE_PAGE(compound && !PageTransHuge(page), page); >>>>>> + >>>>>> + if (likely(!compound)) >>>>>> + nr_pages = 1; >>>>>> + else >>>>>> + nr_pages = folio_nr_pages(folio); >>>>>> + >>>>>> + folio_add_file_rmap_range(folio, page, nr_pages, vma, compound); >>>>>> +} >>>>>> + >>>>>> /** >>>>>> * page_remove_rmap - take down pte mapping from a page >>>>>> * @page: page to remove mapping from >>>>> >>>> >> >>