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[2003:cb:c710:ff00:1a06:80f:733a:e8c6]) by smtp.gmail.com with ESMTPSA id v5-20020a5d43c5000000b0030abe7c36b1sm15151354wrr.93.2023.06.13.05.36.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Jun 2023 05:36:34 -0700 (PDT) Message-ID: <77b2ffeb-732c-229e-0f41-f63f75e43164@redhat.com> Date: Tue, 13 Jun 2023 14:36:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2] mm: compaction: skip memory hole rapidly when isolating migratable pages To: Baolin Wang , akpm@linux-foundation.org Cc: mgorman@techsingularity.net, vbabka@suse.cz, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <770f9f61472b24b6bc89adbd71a77d9cf62bb54f.1686646361.git.baolin.wang@linux.alibaba.com> <838c3066-43e9-2035-cf69-4957481cddda@linux.alibaba.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <838c3066-43e9-2035-cf69-4957481cddda@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 5F36310001A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ryroi8x3eu1tw5sksb9npy17cau3gwtd X-HE-Tag: 1686659799-946178 X-HE-Meta: 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 tRD2Ax2T IWcK5UyWES7+GhlaEGVhJzCIor3BItEQnEmAEnOvCw3A63dNq8f/BdzraZnISNo51xssUETG2K9zyqqP41X213Obq5WScvCVEAnHLt834XkFNJyjDr4itPNV3geKTUT9XtXAhVfk9atRWe0xe4+Cj9xlFg//aMe1o6M8o2+dVhhrL5Lyo9buAamkOGAD3noeFxdcxQIYgYS2butLK0XvN/DdaHoBXzVjfrruxGRKJrPVXzu4Rs3Hltmt+vCs8GuvM1FWDiWOd9gomTjCTS5BAC1iU4tfT1lIfGoebF1OM+0lt7C8ZvJc5/aYgwxSedgWlA1xBXVM/zjlsm5u4XxRK18Tq9F1Wn8bd4Va1Nybn3Nvgz93p1inCT4q46qAdP1L3/V1slgGv+E1dJG642Dwdcg3OddIHdF8WcdEo8/OlNGWCSP7QMBkUTPYb3Q== 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 13.06.23 13:13, Baolin Wang wrote: > > > On 6/13/2023 5:56 PM, David Hildenbrand wrote: >> On 13.06.23 10:55, Baolin Wang wrote: >>> On some machines, the normal zone can have a large memory hole like >>> below memory layout, and we can see the range from 0x100000000 to >>> 0x1800000000 is a hole. So when isolating some migratable pages, the >>> scanner can meet the hole and it will take more time to skip the large >>> hole. From my measurement, I can see the isolation scanner will take >>> 80us ~ 100us to skip the large hole [0x100000000 - 0x1800000000]. >>> >>> So adding a new helper to fast search next online memory section >>> to skip the large hole can help to find next suitable pageblock >>> efficiently. With this patch, I can see the large hole scanning only >>> takes < 1us. >>> >>> [    0.000000] Zone ranges: >>> [    0.000000]   DMA      [mem 0x0000000040000000-0x00000000ffffffff] >>> [    0.000000]   DMA32    empty >>> [    0.000000]   Normal   [mem 0x0000000100000000-0x0000001fa7ffffff] >>> [    0.000000] Movable zone start for each node >>> [    0.000000] Early memory node ranges >>> [    0.000000]   node   0: [mem 0x0000000040000000-0x0000000fffffffff] >>> [    0.000000]   node   0: [mem 0x0000001800000000-0x0000001fa3c7ffff] >>> [    0.000000]   node   0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff] >>> [    0.000000]   node   0: [mem 0x0000001fa4000000-0x0000001fa402ffff] >>> [    0.000000]   node   0: [mem 0x0000001fa4030000-0x0000001fa40effff] >>> [    0.000000]   node   0: [mem 0x0000001fa40f0000-0x0000001fa73cffff] >>> [    0.000000]   node   0: [mem 0x0000001fa73d0000-0x0000001fa745ffff] >>> [    0.000000]   node   0: [mem 0x0000001fa7460000-0x0000001fa746ffff] >>> [    0.000000]   node   0: [mem 0x0000001fa7470000-0x0000001fa758ffff] >>> [    0.000000]   node   0: [mem 0x0000001fa7590000-0x0000001fa7ffffff] >>> >>> Signed-off-by: Baolin Wang >>> --- >>> Changes from v1: >>>   - Fix building errors if CONFIG_SPARSEMEM is not selected. >>>   - Use NR_MEM_SECTIONS instead of '-1' per Huang Ying. >>> --- >>>   include/linux/mmzone.h | 10 ++++++++++ >>>   mm/compaction.c        | 30 +++++++++++++++++++++++++++++- >>>   2 files changed, 39 insertions(+), 1 deletion(-) >>> >>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >>> index 5a7ada0413da..5ff1fa2efe28 100644 >>> --- a/include/linux/mmzone.h >>> +++ b/include/linux/mmzone.h >>> @@ -2000,6 +2000,16 @@ static inline unsigned long >>> next_present_section_nr(unsigned long section_nr) >>>       return -1; >>>   } >>> +static inline unsigned long next_online_section_nr(unsigned long >>> section_nr) >>> +{ >>> +    while (++section_nr <= __highest_present_section_nr) { >>> +        if (online_section_nr(section_nr)) >>> +            return section_nr; >>> +    } >>> + >>> +    return NR_MEM_SECTIONS; >>> +} >>> + >>>   /* >>>    * These are _only_ used during initialisation, therefore they >>>    * can use __initdata ...  They could have names to indicate >>> diff --git a/mm/compaction.c b/mm/compaction.c >>> index 3398ef3a55fe..c31ff6123891 100644 >>> --- a/mm/compaction.c >>> +++ b/mm/compaction.c >>> @@ -229,6 +229,28 @@ static void reset_cached_positions(struct zone >>> *zone) >>>                   pageblock_start_pfn(zone_end_pfn(zone) - 1); >>>   } >>> +#ifdef CONFIG_SPARSEMEM >>> +static unsigned long skip_hole_pageblock(unsigned long start_pfn) >>> +{ >>> +    unsigned long next_online_nr; >>> +    unsigned long start_nr = pfn_to_section_nr(start_pfn); >>> + >>> +    if (online_section_nr(start_nr)) >>> +        return 0; >>> + >>> +    next_online_nr = next_online_section_nr(start_nr); >>> +    if (next_online_nr < NR_MEM_SECTIONS) >>> +        return section_nr_to_pfn(next_online_nr); >>> + >> >> I would simply inline next_online_section_nr and simplify (and add a >> comment): >> >> /* >>  * If the PFN falls into an offline section, return the start PFN of the >>  * next online section. If the PFN falls into an online section or if >>  * there is no next online section, return 0. >>  */ >> static unsigned long skip_hole_pageblock(unsigned long start_pfn) >> { >>     unsigned long nr = pfn_to_section_nr(start_pfn); >> >>     if (online_section_nr(nr)) >>         return 0; >> >>     while (++nr <= __highest_present_section_nr) { >>         if (online_section_nr(nr)) >>             return section_nr_to_pfn(nr); >>     } >>     return 0 >> } >> >> Easier, no? > > Originally I want to add a common helper like next_present_section_nr(), > which can be used by other users. But yes, your suggestion is easier, > and I am fine with that. > >> And maybe just call that function "skip_offline_sections()" then? >> Because we're not operating on pageblocks. > > OK. Thanks. > Feel free to add to the simplified version Acked-by: David Hildenbrand -- Cheers, David / dhildenb