From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f47.google.com (mail-ed1-f47.google.com [209.85.208.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E86A7305063 for ; Wed, 20 Aug 2025 12:42:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755693741; cv=none; b=syUd2NUvEvd22U7vCT6PbqWfw9lti2lbyPfAlOkaqks+4TUhVm1a2ZwM8LoXXXmrwlSnAwhJihmILUZPrqp0Il4X/fjgj1IUD/5Pt4+EBQ2chLH1pq3hFVEoRxCdeqv1JqK8KGfF3if7ijPe+Z+0f+Q5n//9Op/9bmowp9o+1oA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755693741; c=relaxed/simple; bh=wfUj5GVqJdy8Gzu7HZkb5EvyfjAxA67sUfDfZ4Afc9o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qmb/ZexvvGXfFOWPFRjy6JZ3olXIcVJexH3gHBNDjNY/5eRI4HrZ6X+kiCyKizsdoQgC/nB3oOL3547AyulUL1RrKRUu0QIhJv1+VMVt4fYGlMgUqnFjk77sJZx0e5yB3/iQ/2YGjLWtvLFFGV1SzKE/mX7efod74F39N5cLbyQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=lpRXpCX5; arc=none smtp.client-ip=209.85.208.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="lpRXpCX5" Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-6188b793d21so9668320a12.3 for ; Wed, 20 Aug 2025 05:42:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1755693736; x=1756298536; darn=lists.linux.dev; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=BIg9W/3Kh0nknE9bg10iXxQ5gJtP6ZAIJOJFszr9STA=; b=lpRXpCX5fqG6u0s3PbIn46nGyi8k9lrkJ71Iu4wH0TQHGzvwNFGsbY1O60+POSRJod /1yEZV8ZWQvoQlEnLP4z+Bsq4st0nFKRc0fwXiz/IQxtxtLOhcGGeWOiI62a9rNlXrqg 7FrrP1nQVlN9fEX9/f5PhxU7X0IOZc26dpfwQ24NcFX9a/uZHV4cxZmWLd00KR9lfA5n TFec2A2cLGTtN+d2H5KkSTl2SklI0JC02MTK147NGa7Hapj8T0Mwx1vkKeQRsxGTbQh7 YX/jLePMTpDY4NVr28JQjmBLv0MUCViGIqrW/j3NkjLAaWuf2qayzDBp4ugDG7oHamG0 XOvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1755693736; x=1756298536; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=BIg9W/3Kh0nknE9bg10iXxQ5gJtP6ZAIJOJFszr9STA=; b=UlJ6jOJFeUhe+DckcEE3uYd9g/mLe1hWr3FOCwEoAQUlooHGlHFa6Fc1Pr58qDdN/4 Nj6zODscPfP3586LPGRe/KNNWLcHRxCMiFuGoxuVkqWzSbPwgaXe/sUEPmtdlCagWlTg nlzOg6AYQLoE3QWuNf+HyA9iQMac+27yg1P842gm58VxXP+rvHF9PsSCHvOXmEfLrkIk /TzNfKby3U2x8MYK2cH44bmAppPbHpSibRljO5YQd4DNzwGeAX7RzyFBZddWSGTXlawv UXjuxxcFnhj3xT60Qu6tSonLPXUZ/x/2tvzjoTQCtp/VbkJeDax5NTEqe3TRFgsnSx+E /ykw== X-Forwarded-Encrypted: i=1; AJvYcCXaqIF4jNkKienSdpCPuP7nzJhgBjaQBl4ufltW92BPlEQCEJDkH2BiDUKpobeurOdYOQdi@lists.linux.dev X-Gm-Message-State: AOJu0YzHVUmr3gfcsNlA3BWqEJ4L5mi7bkCGqR9uKoTSFYGKV29PE7G1 WsaGqGkB719PZDaP+7KLTF3fmpLGxYvh07niXAuTgWBDkB6z2j5+8YqK X-Gm-Gg: ASbGncths1SN23bZ5kojlZPQkyzWlWWeXDEe5/XeCoQUDv/TyUcHAp/lP1jToaCoV0c 2qeIQ1u3yADztyAp/XLVd6A/TwrsVG643ZGAo+jPp+Lq5/7Us1G8Vx+HhznXsxpk7XVge4VhanK YJO0WWy7FBqx/JEX+2GLIZ5yuLA+lY0Hjq900Ky2DNNuJogSmAJqnNFM2Uf5n1zkOWscg1abHpb 92TYECq9p1sII/Ap/RvJ0A5W31+/PjMYowxUDNxLpyYm6qA0PQY7Qd8qbbbS1zC4g1NOCTikOOY 6SySo5pFsgeNcZFdjlan97jp8wFOA+rrI1oLd9skyB8gXtxpjKsgAfpSN/WMIisJqx7p25C8yvg OUzYGpo4CSuVY01LcP4FYBmTSUI00meTsEmSR X-Google-Smtp-Source: AGHT+IHHRa/Wjm92m9kTtxGRWzJ7agHg8ZuSbyEGNlj7C81CaI3UVA8ffbMZiBB1+byaZJtVfu6Ixw== X-Received: by 2002:a05:6402:4306:b0:618:aed3:38a with SMTP id 4fb4d7f45d1cf-61a9782d02cmr2281770a12.31.1755693735970; Wed, 20 Aug 2025 05:42:15 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-61a758bff1csm3633444a12.56.2025.08.20.05.42.15 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 20 Aug 2025 05:42:15 -0700 (PDT) Date: Wed, 20 Aug 2025 12:42:15 +0000 From: Wei Yang To: Mike Rapoport Cc: Wei Yang , linux-mm@kvack.org, Andrew Morton , Bill Wendling , Daniel Jordan , Justin Stitt , Michael Ellerman , Miguel Ojeda , Nathan Chancellor , Nick Desaulniers , linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH 1/4] mm/mm_init: use deferred_init_memmap_chunk() in deferred_grow_zone() Message-ID: <20250820124215.igq7ug4juiomjyng@master> Reply-To: Wei Yang References: <20250818064615.505641-1-rppt@kernel.org> <20250818064615.505641-2-rppt@kernel.org> <20250819095223.ckjdsii4gc6u4nec@master> <20250819235158.mgei7l4yraheech4@master> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) On Wed, Aug 20, 2025 at 12:20:10PM +0300, Mike Rapoport wrote: >On Tue, Aug 19, 2025 at 11:51:58PM +0000, Wei Yang wrote: >> On Tue, Aug 19, 2025 at 01:54:46PM +0300, Mike Rapoport wrote: >> >On Tue, Aug 19, 2025 at 09:52:23AM +0000, Wei Yang wrote: >> >> Hi, Mike >> >> >> >> After going through the code again, I have some trivial thoughts to discuss >> >> with you. If not right, please let me know. >> >> >> >> On Mon, Aug 18, 2025 at 09:46:12AM +0300, Mike Rapoport wrote: >> >> >> >> In the file above this line, there is a compare between first_deferred_pfn and >> >> its original value after grab pgdat_resize_lock. >> > >> >Do you mean this one: >> > >> > if (first_deferred_pfn != pgdat->first_deferred_pfn) { >> > pgdat_resize_unlock(pgdat, &flags); >> > return true; >> > } >> > >> >> Yes. >> >> I am thinking something like this: >> >> if (first_deferred_pfn != pgdat->first_deferred_pfn || >> first_deferred_pfn == ULONG_MAX) >> >> This means >> >> * someone else has grow zone before we grab the lock >> * or the whole zone has already been initialized > >deferred_grow_zone() can be called only before deferred_init_memmap(), so >it's very unlikely that a zone will be completely initialized here. We >start with at least one section with each deferred zone and every call to >deferred_grow_zone() adds a section. > >And even if that was a case and first_deferred_pfn is ULONG_MAX, the loop >below will end immediately, so I don't think additional condition here >would be helpful. > I think you are right. >> >> I am thinking to compare first_deferred_pfn with ULONG_MAX, as it compared in >> >> deferred_init_memmap(). This indicate this zone has already been initialized >> >> totally. >> > >> >It may be another CPU ran deferred_grow_zone() and won the race for resize >> >lock. Then pgdat->first_deferred_pfn will be larger than >> >first_deferred_pfn, but still not entire zone would be initialized. >> > >> >> Current code guard this by spfn < zone_end_pfn(zone). Maybe a check ahead >> >> would be more clear? >> > >> >Not sure I follow you here. The check that we don't pass zone_end_pfn is >> >inside the loop for every section we initialize. >> > >> >> In case the zone has been initialized totally, first_deferred_pfn = ULONG_MAX. >> >> Then we come to the loop with initial state: >> >> spfn = ULONG_MAX >> epfn = 0 (which is wrap around) >> >> And loop condition check (spfn < zone_end_pfn(zone)) is false, so the loop is >> skipped. This is how we handle a fully initialized zone now. >> >> Would this be a little un-common? > >Why? The important thing is (spfn < zone_end_pfn(zone)) is false, and I >think that's good enough. > Well, no more else. >> >> > >> >> >- /* If the zone is empty somebody else may have cleared out the zone */ >> >> >- if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, >> >> >- first_deferred_pfn)) { >> >> >- pgdat->first_deferred_pfn = ULONG_MAX; >> >> >- pgdat_resize_unlock(pgdat, &flags); >> >> >- /* Retry only once. */ >> >> >- return first_deferred_pfn != ULONG_MAX; >> >> >+ /* >> >> >+ * Initialize at least nr_pages_needed in section chunks. >> >> >+ * If a section has less free memory than nr_pages_needed, the next >> >> >+ * section will be also initalized. >> >> Nit, one typo here. s/initalized/initialized/ > >Thanks, will fix. > >-- >Sincerely yours, >Mike. -- Wei Yang Help you, Help me