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[2003:cb:c70a:2700:1d28:26c3:b272:fcc6]) by smtp.gmail.com with ESMTPSA id c186-20020a1c35c3000000b0039c948dbb61sm1757510wma.26.2022.06.15.02.35.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Jun 2022 02:35:10 -0700 (PDT) Message-ID: <62aef8a9-aa21-37ec-83b5-9dd9fc729890@redhat.com> Date: Wed, 15 Jun 2022 11:35:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 To: Muchun Song , corbet@lwn.net, akpm@linux-foundation.org, paulmck@kernel.org, mike.kravetz@oracle.com, osalvador@suse.de Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com References: <20220520025538.21144-1-songmuchun@bytedance.com> <20220520025538.21144-2-songmuchun@bytedance.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v2 1/2] mm: memory_hotplug: enumerate all supported section flags In-Reply-To: <20220520025538.21144-2-songmuchun@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655285716; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=GDQf++O5Povpr9/MTkGUovRB/Hb0K7Xk0pSbUnRMSQo=; b=cbs8tn198pBgQAsP21IKkREpSaarjJIWQy/4zryXbZIb5cUJ6d3UZSL+Aj+xICtHvSjdvZ LC2ab7pfYTEINN93gQw6pNrjjwWZFD4OOgBTOWAUEL7+BMIHfhFuelAruwp0HTkxTMbPWE A5QeCYB2pa0cbGrlJvzl48s5qi9yjDo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655285716; a=rsa-sha256; cv=none; b=BC5xr1RawQ+hfBEoobLqKZoz+FM+pUVnDa72xQriYQALisZ+2qJH8uTlrrvfvfdDTzq6Ei WnQbkbNzF/WeiWOAbDnW42uImhVG2hsLlE3JLIm5K68hxCBwvrL0XIa3AUXuUzNqjUUeLC vGnhTNZISy5bGTl14sFW2C2yc89FV4w= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bXuln9yA; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf05.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bXuln9yA; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf05.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam12 X-Rspam-User: X-Stat-Signature: kuoaro5mxjytqszuawrocygdqy7xfif4 X-Rspamd-Queue-Id: D8C4A100080 X-HE-Tag: 1655285715-974257 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 20.05.22 04:55, Muchun Song wrote: > We are almost running out of section flags, only one bit is available in > the worst case (powerpc with 256k pages). However, there are still some > free bits (in ->section_mem_map) on other architectures (e.g. x86_64 has > 10 bits available, arm64 has 8 bits available with worst case of 64K > pages). We have hard coded those numbers in code, it is inconvenient to > use those bits on other architectures except powerpc. So transfer those > section flags to enumeration to make it easy to add new section flags in > the future. Also, move SECTION_TAINT_ZONE_DEVICE into the scope of > CONFIG_ZONE_DEVICE to save a bit on non-zone-device case. > > Signed-off-by: Muchun Song Sorry for the late reply. This looks overly complicated to me. IOW, staring at that patch I don't quite like what I am seeing. Something like the following is *a lot* easier to read than some MAPPER macro magic. What speaks against it? /* * Section bits use the lower unused bits in the ->section_mem_map */ enum { SECTION_MARKED_PRESENT_BIT = 0, SECTION_HAS_MEM_MAP_BIT, ... #ifdef ZONE_DEVICE SECTION_TAINT_ZONE_DEVICE_BIT #endif } #define SECTION_MARKED_PRESENT (1ULL << SECTION_MARKED_PRESENT_BIT) ... #ifdef ZONE_DEVICE #define SECTION_TAINT_ZONE_DEVICE (1ULL << SECTION_TAINT_ZONE_DEVICE_BIT) #endif /* ZONE_DEVICE */ > --- > include/linux/kconfig.h | 1 + > include/linux/mmzone.h | 54 +++++++++++++++++++++++++++++++++++++++++-------- > mm/memory_hotplug.c | 6 ++++++ > 3 files changed, 53 insertions(+), 8 deletions(-) > > diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h > index 20d1079e92b4..7044032b9f42 100644 > --- a/include/linux/kconfig.h > +++ b/include/linux/kconfig.h > @@ -10,6 +10,7 @@ > #define __LITTLE_ENDIAN 1234 > #endif > > +#define __ARG_PLACEHOLDER_ 0, > #define __ARG_PLACEHOLDER_1 0, > #define __take_second_arg(__ignored, val, ...) val > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 299259cfe462..2cf2a76535ab 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1422,16 +1422,47 @@ extern size_t mem_section_usage_size(void); > * (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the > * worst combination is powerpc with 256k pages, > * which results in PFN_SECTION_SHIFT equal 6. > - * To sum it up, at least 6 bits are available. > + * To sum it up, at least 6 bits are available on all architectures. > + * However, we can exceed 6 bits on some other architectures except > + * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available > + * with the worst case of 64K pages on arm64) if we make sure the > + * exceeded bit is not applicable to powerpc. > */ > -#define SECTION_MARKED_PRESENT (1UL<<0) > -#define SECTION_HAS_MEM_MAP (1UL<<1) > -#define SECTION_IS_ONLINE (1UL<<2) > -#define SECTION_IS_EARLY (1UL<<3) > -#define SECTION_TAINT_ZONE_DEVICE (1UL<<4) > -#define SECTION_MAP_LAST_BIT (1UL<<5) > +#define ENUM_SECTION_FLAG(MAPPER) \ > + MAPPER(MARKED_PRESENT) \ > + MAPPER(HAS_MEM_MAP) \ > + MAPPER(IS_ONLINE) \ > + MAPPER(IS_EARLY) \ > + MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \ > + MAPPER(MAP_LAST_BIT) > + > +#define __SECTION_SHIFT_FLAG_MAPPER_0(x) > +#define __SECTION_SHIFT_FLAG_MAPPER_1(x) SECTION_##x##_SHIFT, > +#define __SECTION_SHIFT_FLAG_MAPPER(x, ...) \ > + __PASTE(__SECTION_SHIFT_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > + > +#define __SECTION_FLAG_MAPPER_0(x) > +#define __SECTION_FLAG_MAPPER_1(x) SECTION_##x = BIT(SECTION_##x##_SHIFT), > +#define __SECTION_FLAG_MAPPER(x, ...) \ > + __PASTE(__SECTION_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > + > +enum { > + /* > + * Generate a series of enumeration flags like SECTION_$name_SHIFT. > + * Each entry in ENUM_SECTION_FLAG() macro will be generated to one > + * enumeration iff the 2nd parameter of MAPPER() is defined or absent. > + * The $name comes from the 1st parameter of MAPPER() macro. > + */ > + ENUM_SECTION_FLAG(__SECTION_SHIFT_FLAG_MAPPER) > + /* > + * Generate a series of enumeration flags like: > + * SECTION_$name = BIT(SECTION_$name_SHIFT) > + */ > + ENUM_SECTION_FLAG(__SECTION_FLAG_MAPPER) > +}; > + > #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > -#define SECTION_NID_SHIFT 6 > +#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT_SHIFT > > static inline struct page *__section_mem_map_addr(struct mem_section *section) > { > @@ -1470,12 +1501,19 @@ static inline int online_section(struct mem_section *section) > return (section && (section->section_mem_map & SECTION_IS_ONLINE)); > } > > +#ifdef CONFIG_ZONE_DEVICE > static inline int online_device_section(struct mem_section *section) > { > unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE; > > return section && ((section->section_mem_map & flags) == flags); > } > +#else > +static inline int online_device_section(struct mem_section *section) > +{ > + return 0; > +} > +#endif > > static inline int online_section_nr(unsigned long nr) > { > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 1213d0c67a53..3b360eda933f 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -672,12 +672,18 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon > > } > > +#ifdef CONFIG_ZONE_DEVICE > static void section_taint_zone_device(unsigned long pfn) > { > struct mem_section *ms = __pfn_to_section(pfn); > > ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE; > } > +#else > +static inline void section_taint_zone_device(unsigned long pfn) > +{ > +} > +#endif > > /* > * Associate the pfn range with the given zone, initializing the memmaps -- Thanks, David / dhildenb