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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38F7DC433F5 for ; Wed, 25 May 2022 11:10:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5CC348D0003; Wed, 25 May 2022 07:10:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 59E548D0001; Wed, 25 May 2022 07:10:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 48F128D0003; Wed, 25 May 2022 07:10:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 3696C8D0001 for ; Wed, 25 May 2022 07:10:55 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 06525611B1 for ; Wed, 25 May 2022 11:10:55 +0000 (UTC) X-FDA: 79503998070.28.3D4F7C7 Received: from mail-ej1-f50.google.com (mail-ej1-f50.google.com [209.85.218.50]) by imf11.hostedemail.com (Postfix) with ESMTP id 6F44840019 for ; Wed, 25 May 2022 11:10:47 +0000 (UTC) Received: by mail-ej1-f50.google.com with SMTP id y13so40226524eje.2 for ; Wed, 25 May 2022 04:10:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6bM29bpY/71jdlbrQel2iwJKKK8Us/LpmJJm4YVlh+M=; b=W+1xcp/Zcd/MC4E23T4a4oyTj/9bSBGcGq6DI9X4va/M5ecZShy29tcu7LYgpVpX7D 74TJlhFPaT7zmfx1rJY3/oTtZ6+ZK5uWe/0uwWX+l6bsytePcBshhhyI5u3rQUkR2K7f jVkOavworgNrJxcW7HgodojKO/ifovkRJUDhG7L5YoCrfHCbkMmX91WdrUtnWV6PlPJM s45kpLTynJH8/6oArhD+bAGRJMRtr2x3R4cdYqm/cI8WIWS5JU+CTiSlv4TqtvfEid1c ky/nxuHB5KorkViGGOUcMtXKdIbNflzIX75ZAvNrZxa1oaNe2r95KKh+tmkZigxd11Ie Oxhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6bM29bpY/71jdlbrQel2iwJKKK8Us/LpmJJm4YVlh+M=; b=PVDP/D3MmA4BzQ6m0ozvyKaGrJcAOtbW8RqU5P4gd/ogH1UAK8iwoR4fPPlGgLi6b2 gBtSdllk4o17yPsXwzPquWN57cKScrAf3NXX1BJ+w4DmT4SGzvZCJt2NRG64cYi6Jge8 TUltvMKq3/UX8iS7nRH+bT+rS0skt1gMjNLEZjvH7IBpSAPPDQDxsU6/3kgnaAOAP0vS qpWTwes8OT0iCyiowpsOnHCKmztHRXgCA4eeB/Y+KPpAaE/HW3ELGqfXUUangWDIxEc6 s39S/6q62aErBybrMOOpGZwR4dd6OumvYiXkh8f7yF/CvEQBhCh6ed6h0HVKBn5jG1h2 TAOg== X-Gm-Message-State: AOAM5331erLedhutYX6onA3TdgUgOBdnraGl65+MtW7NNxlwMg6OKS4s 0FTCfRoJgstnk2u5QZLbM9WiVaQ37oDENACat5o= X-Google-Smtp-Source: ABdhPJzvlsX5kXtlav7uMuUZUY4Ce9XVcz4UD+g+LXg1eAxeHlB/Q1YlVAzOZWcHPIiGxSDqu6j1mbLWSr3lUxR2PEA= X-Received: by 2002:a17:907:3f92:b0:6ff:19ff:a528 with SMTP id hr18-20020a1709073f9200b006ff19ffa528mr136512ejc.91.1653477053132; Wed, 25 May 2022 04:10:53 -0700 (PDT) MIME-Version: 1.0 References: <20220524071403.128644-1-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Wed, 25 May 2022 23:10:41 +1200 Message-ID: Subject: Re: [PATCH] arm64: enable THP_SWAP for arm64 To: Catalin Marinas Cc: Andrew Morton , Will Deacon , Linux-MM , LAK , LKML , hanchuanhua , =?UTF-8?B?5byg6K+X5piOKFNpbW9uIFpoYW5nKQ==?= , =?UTF-8?B?6YOt5YGl?= , Barry Song , "Huang, Ying" , Minchan Kim , Johannes Weiner , Hugh Dickins , Shaohua Li , Rik van Riel , Andrea Arcangeli , Steven Price Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="W+1xcp/Z"; spf=pass (imf11.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.218.50 as permitted sender) smtp.mailfrom=21cnbao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: n5k1zpq77ebt7n96ug55imu7w4aurxpk X-Rspamd-Queue-Id: 6F44840019 X-Rspamd-Server: rspam01 X-HE-Tag: 1653477047-112903 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 Wed, May 25, 2022 at 7:14 AM Catalin Marinas wrote: > > On Tue, May 24, 2022 at 10:05:35PM +1200, Barry Song wrote: > > On Tue, May 24, 2022 at 8:12 PM Catalin Marinas wrote: > > > On Tue, May 24, 2022 at 07:14:03PM +1200, Barry Song wrote: > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > > index d550f5acfaf3..8e3771c56fbf 100644 > > > > --- a/arch/arm64/Kconfig > > > > +++ b/arch/arm64/Kconfig > > > > @@ -98,6 +98,7 @@ config ARM64 > > > > select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) > > > > select ARCH_WANT_LD_ORPHAN_WARN > > > > select ARCH_WANTS_NO_INSTR > > > > + select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES > > > > > > I'm not opposed to this but I think it would break pages mapped with > > > PROT_MTE. We have an assumption in mte_sync_tags() that compound pages > > > are not swapped out (or in). With MTE, we store the tags in a slab > > > > I assume you mean mte_sync_tags() require that THP is not swapped as a whole, > > as without THP_SWP, THP is still swapping after being splitted. MTE doesn't stop > > THP from swapping through a couple of splitted pages, does it? > > That's correct, split THP page are swapped out/in just fine. > > > > object (128-bytes per swapped page) and restore them when pages are > > > swapped in. At some point we may teach the core swap code about such > > > metadata but in the meantime that was the easiest way. > > > > If my previous assumption is true, the easiest way to enable THP_SWP > > for this moment might be always letting mm fallback to the splitting > > way for MTE hardware. For this moment, I care about THP_SWP more as > > none of my hardware has MTE. > > > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > > index 45c358538f13..d55a2a3e41a9 100644 > > --- a/arch/arm64/include/asm/pgtable.h > > +++ b/arch/arm64/include/asm/pgtable.h > > @@ -44,6 +44,8 @@ > > __flush_tlb_range(vma, addr, end, PUD_SIZE, false, 1) > > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > > > +#define arch_thp_swp_supported !system_supports_mte > > + > > /* > > * Outside of a few very special situations (e.g. hibernation), we always > > * use broadcast TLB invalidation instructions, therefore a spurious page > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > index 2999190adc22..064b6b03df9e 100644 > > --- a/include/linux/huge_mm.h > > +++ b/include/linux/huge_mm.h > > @@ -447,4 +447,16 @@ static inline int split_folio_to_list(struct folio *folio, > > return split_huge_page_to_list(&folio->page, list); > > } > > > > +/* > > + * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to > > + * limitations in the implementation like arm64 MTE can override this to > > + * false > > + */ > > +#ifndef arch_thp_swp_supported > > +static inline bool arch_thp_swp_supported(void) > > +{ > > + return true; > > +} > > +#endif > > + > > #endif /* _LINUX_HUGE_MM_H */ > > diff --git a/mm/swap_slots.c b/mm/swap_slots.c > > index 2b5531840583..dde685836328 100644 > > --- a/mm/swap_slots.c > > +++ b/mm/swap_slots.c > > @@ -309,7 +309,7 @@ swp_entry_t get_swap_page(struct page *page) > > entry.val = 0; > > > > if (PageTransHuge(page)) { > > - if (IS_ENABLED(CONFIG_THP_SWAP)) > > + if (IS_ENABLED(CONFIG_THP_SWAP) && arch_thp_swp_supported()) > > get_swap_pages(1, &entry, HPAGE_PMD_NR); > > goto out; > > I think this should work and with your other proposal it would be > limited to MTE pages: > > #define arch_thp_swp_supported(page) (!test_bit(PG_mte_tagged, &page->flags)) > > Are THP pages loaded from swap as a whole or are they split? IIRC the i can confirm thp is written as a whole through: [ 90.622863] __swap_writepage+0xe8/0x580 [ 90.622881] swap_writepage+0x44/0xf8 [ 90.622891] pageout+0xe0/0x2a8 [ 90.622906] shrink_page_list+0x9dc/0xde0 [ 90.622917] shrink_inactive_list+0x1ec/0x3c8 [ 90.622928] shrink_lruvec+0x3dc/0x628 [ 90.622939] shrink_node+0x37c/0x6a0 [ 90.622950] balance_pgdat+0x354/0x668 [ 90.622961] kswapd+0x1e0/0x3c0 [ 90.622972] kthread+0x110/0x120 but i have never got a backtrace in which thp is loaded as a whole though it seems the code has this path: int swap_readpage(struct page *page, bool synchronous) { ... bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL); bio->bi_iter.bi_sector = swap_page_sector(page); bio->bi_end_io = end_swap_bio_read; bio_add_page(bio, page, thp_size(page), 0); ... submit_bio(bio); } > splitting still happens but after the swapping out finishes. Even if > they are loaded as 4K pages, we still have the mte_save_tags() that only > understands small pages currently, so rejecting THP pages is probably > best. as anyway i don't have a mte-hardware to do a valid test to go any further, so i will totally disable thp_swp for hardware having mte for this moment in patch v2. > > -- > Catalin Thanks Barry