From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 058ECC43458 for ; Tue, 14 Jul 2026 09:45:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EF3A86B0092; Tue, 14 Jul 2026 05:45:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ECAB36B0093; Tue, 14 Jul 2026 05:45:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E09166B009B; Tue, 14 Jul 2026 05:45:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id B6FA66B0092 for ; Tue, 14 Jul 2026 05:45:27 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 40296C02DF for ; Tue, 14 Jul 2026 09:45:27 +0000 (UTC) X-FDA: 84986899494.01.8064D4C Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) by imf28.hostedemail.com (Postfix) with ESMTP id 2FE4DC0009 for ; Tue, 14 Jul 2026 09:45:25 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=s2kVBwVl; spf=pass (imf28.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784022325; 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=mekORx+dFKRiABrAy+XEgciHwWSjZPvElZQGPDy01aI=; b=pw/2/dWTLLmuaQQb5RdMcBUjFhU56COuYo3a0XJsDDkKnbf2iWRvlM0vTe6c4W7iqihwBc Bu7uq6ErBy3o595SFOX0uw+0fVNQIEk4NTNOpLHwAo6z/eVI6euHf+r9s58AxkJkHdMqVL +bo46NJQofL9gAGvwaX4LKarYKZ1K2U= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=s2kVBwVl; spf=pass (imf28.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784022325; b=tKzvvX+7SnnAXlCSObeZ89Mzwzo0f53ts1Qa4BXGJVnqLjcurzy68fafj/LvP8q1odX731 CPqRrfMJTu1ioPaze64+Fszyzj0x0fL3QS1YdVqbWaVE2f5nBUPH1Ls947NcG+iz1gjjim AfayOtibaop+W/hk7nio7OH2+9KOg9Q= Message-ID: <04f5b50a-a526-4644-b9f0-c54a0d6db702@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784022323; h=from:from: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; bh=mekORx+dFKRiABrAy+XEgciHwWSjZPvElZQGPDy01aI=; b=s2kVBwVl7nJQg4Gb/Kqxo1bPGuZQp8vx9e/9dh096WOea1GmNZvCyunI+kd7T22YqJYDA/ NKH2dTJV7HWZL661cCIPgju0vw80HFbKnXFteGddtiUZO3JDANIoYLOYb9ukTtCzgsEIpr nc7fRXOdZErHcdm3A2EnLN4UvV7I5T4= Date: Tue, 14 Jul 2026 17:45:17 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v6 8/8] mm: use memcpy_nt() in zone-device template copies To: Li Zhe Cc: linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, apopple@nvidia.com, arnd@arndb.de, balbirs@nvidia.com, bp@alien8.de, dave.hansen@linux.intel.com, david@kernel.org, kees@kernel.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org References: <20260709112520.24857-1-lizhe.67@bytedance.com> <20260709112520.24857-9-lizhe.67@bytedance.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20260709112520.24857-9-lizhe.67@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2FE4DC0009 X-Stat-Signature: c3sek3z15n6pky5ffu3ehuampt98arzi X-HE-Tag: 1784022325-953599 X-HE-Meta: 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 aifr8fF3 WGoLU0CSlTCPEivezJjPPC+lXyD/XOqPqwghipyAQfFSAk+B+lGqBdYCJhs8SpzvNmJA5W1h1y3fxol+3lnfxm5rjV8HRzgWbAdTOow1oQjbPpKI/ED996vQD93zYJMBZux59P0U1x1FgmPiuymHtPe73xC2Av0GoR0/72SPwreaLabOoZgwVAwjPxkw9vKlKZfb4jwGjU1hLyYIEIwib+FodObNwkioHVdt4WCyCP3JEeND4ruG5tTJ8xpLV2j8DOdXpK7/eJvngXxrpNa5QwsX/90e0IpTv9Wo1 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/7/9 19:25, Li Zhe wrote: > The template fast path currently uses memcpy() for the actual struct > page copy. Switch zone_device_page_init_from_template() to memcpy_nt() > and add memcpy_nt_drain() before memmap_init_compound(), before > prep_compound_head() updates overlapping tail metadata, and before > returning from memmap_init_zone_device(). > > ZONE_DEVICE memmap initialization is largely write-once: each struct > page is populated once, and most destination cachelines are not expected > to be reused immediately afterwards. On x86, a regular cached memcpy() > can therefore incur write-allocate traffic by pulling destination > cachelines into the cache before writeback, and can populate the cache > with data that has little near-term reuse. Using memcpy_nt() lets this > path request non-temporal stores for that copy pattern, which can reduce > cache pollution and avoid part of the associated write-allocate > overhead, while architectures without a specialized backend still fall > back to memcpy(). > > When memcpy_nt() maps to non-temporal stores, order those stores before > memmap_init_compound(), before prep_compound_head() updates overlapping > compound metadata, and before returning from memmap_init_zone_device(). > > Keep sanitized builds on the slow path so KASAN/KMSAN retain their > instrumented stores. > > Tested in a VM with a 100 GB fsdax namespace device configured with > map=dev and a 100 GB devdax namespace (align=2097152) on Intel Ice Lake > server. > > Test procedure: > Rebind the nd_pmem and dax_pmem driver 30 times and collect the memmap > initialization time from the pr_debug() output of > memmap_init_zone_device(). > > Base(v7.2-rc1): > First binding for nd_pmem driver: 1456 ms > Average of subsequent rebinds: 244.28 ms > > First binding for dax_pmem driver: 1462 ms > Average of subsequent rebinds: 273.31 ms > > With this series: > First binding for nd_pmem driver: 1272 ms > Average of subsequent rebinds: 96.79 ms > > First binding for dax_pmem driver: 1354 ms > Average of subsequent rebinds: 119.04 ms > > This reduces the average rebind time by about 60.4% for nd_pmem and > 56.4% for dax_pmem. > > Signed-off-by: Li Zhe > --- > mm/mm_init.c | 39 +++++++++++++++++++++++++++++++++++++-- > 1 file changed, 37 insertions(+), 2 deletions(-) > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index fb855bb0437a..addb4969587e 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1067,11 +1067,21 @@ static void __ref zone_device_page_init_slow(struct page *page, > > static inline bool zone_device_page_init_optimization_enabled(void) > { > + /* > + * Keep sanitized builds on the slow path so their stores stay > + * instrumented. > + */ > + if (IS_ENABLED(CONFIG_KASAN) || IS_ENABLED(CONFIG_KMSAN)) > + return false; It is not a major concern if struct page initialization lacks KASAN or KMSAN instrumentation. To keep things simple, let's just entirely remove zone_device_page_init_optimization_enabled() to simplify the code. Thanks. > + > /* > * The template fast path copies a preinitialized struct page image. > * Skip it when the page_ref_set tracepoint is enabled. > */ > - return !page_ref_tracepoint_active(page_ref_set); > + if (page_ref_tracepoint_active(page_ref_set)) > + return false; > + > + return true; > } > > static inline void zone_device_tail_page_init(struct page *page, > @@ -1110,7 +1120,7 @@ static void zone_device_page_init_from_template(struct page *page, > * to the destination page. > */ > zone_device_page_update_template(template, pfn); > - memcpy(page, template, sizeof(*page)); > + memcpy_nt(page, template, sizeof(*page)); > } > > /* > @@ -1179,6 +1189,15 @@ static void __ref memmap_init_compound(struct page *head, > &template); > } > } > + > + /* > + * When the template path is enabled, order the preceding tail-page copies > + * before prep_compound_head() updates the overlapping compound metadata > + * in the first tail-page descriptors. If memcpy_nt() fell back to > + * regular cached stores, memcpy_nt_drain() may be a no-op. > + */ > + if (use_template) > + memcpy_nt_drain(); > prep_compound_head(head, order); > } > > @@ -1238,10 +1257,26 @@ void __ref memmap_init_zone_device(struct zone *zone, > if (pfns_per_compound == 1) > continue; > > + /* > + * When the template path is enabled, order the preceding head-page copy > + * before memmap_init_compound(), which immediately updates compound-head > + * metadata. If memcpy_nt() fell back to regular cached stores, > + * memcpy_nt_drain() may be a no-op. > + */ > + if (use_template) > + memcpy_nt_drain(); > + > memmap_init_compound(page, pfn, zone_idx, nid, pgmap, > compound_nr_pages(pfn, altmap, pgmap), > use_template); > } > + /* > + * Ensure any prior template copies are ordered before returning. > + * On architectures where memcpy_nt() used regular cached stores, > + * memcpy_nt_drain() may be a no-op. > + */ > + if (use_template) > + memcpy_nt_drain(); > > pageblock_migratetype_init_range(start_pfn, nr_pages, MIGRATE_MOVABLE); > > -- > 2.20.1 >