From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f170.google.com (mail-pf1-f170.google.com [209.85.210.170]) (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 1548114CAB3 for ; Fri, 23 Feb 2024 22:09:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708726186; cv=none; b=J3CMYvv9W36b0bZDvfnFDzDsVq4KGoXznXyI1fu0U3BGojlQS7Y9lOqMkyy/scPjwQKDSXR3Dmc8UuoZ4vVc5lpxzK36rkept7AdzmSERfiYUospMHU6PSNYC+IAAyOOfbqlz5t1drdfSbdOQiIitHV4ik+R2uxLA3NsY/qq/qs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708726186; c=relaxed/simple; bh=NfaUGlHI9XLsk1nlMEAR7M/7M17hVAq68eUm+2SFQS4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dG8scCuFEOXhIcmDh7XrDhD9HCUbuIrW2Dq6SuulbcBzWP45RVfa2Sy3QY3jHWuLRs41SblDt6L/z92ZKlH2EpR/QZoqMnJN/BdYnLY6Oy97ZcFCFASc2UI363PqhA099jy9KrwMElk/0PepRHdhO95mJqsRYsglbfPX0M1RrqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=VigXcZLV; arc=none smtp.client-ip=209.85.210.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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="VigXcZLV" Received: by mail-pf1-f170.google.com with SMTP id d2e1a72fcca58-6e4560664b5so1072320b3a.1 for ; Fri, 23 Feb 2024 14:09:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1708726184; x=1709330984; darn=lists.linux.dev; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=eDQUYGjK0gcC/i45nvgEKWYFzF6rZTJ86bsg/M9a66I=; b=VigXcZLV7zXQeDNV+iks0v4KsxZ/8PBTlQzmw5KP4mXzO8jTwA12gLGUq+8d5eZnZy h4oMH7geDVkvXbmk7i0rnpK3abshycY4kYCTRaD8yPk7TCwTNTTKgyNN3ESOX5i8gg+W WlWWowpQPV3Uj8A3EPAK5DOCNKbETLgXVtmYGt0zJgRVf2517/n3iTXs46UfyMNLE2z0 IOEsQpxEpsq8OMQXWprPE2sK9y+miih9DaXW2no1a58pNveP/n8pJLKEJjqNJPmsu5vU 0kYhtgul3bNq/KdE78/GPKFsq/410U0HaFceRdvDaGZGYTcdunlT0BIdBRfRMzWFerQ2 j1CA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708726184; x=1709330984; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=eDQUYGjK0gcC/i45nvgEKWYFzF6rZTJ86bsg/M9a66I=; b=jbsjqq/gS1PdqTBQ7VrtyJP0Q0cs5eTbErNL642RWuc6BEZIEOhiqzUTN0YjytPtbU w7ILY5XzOwTQNwj+04rtfUE2d6/H49I5qOsMMG7Q7MngbowjIiFHUL5x1GOJqWFNyqpv eSRF7nIA6SPb6fPADdd0GVUIKmpsaIyMp+uzLhoqO++3AyRxxCmOVjmfiiX+1kmblale EkxXNFpiOTBJZQ7CO4kkVLaNz8OtMtWalF8aNgVxbl24y04ETHTROKccBPAFq2ctrenD OsS3hX50D/JKHv2yHKFpEWtzgOmFewqCfPpta2cSBYnRJVcei2kSRh7XAF+wLyBhNPsp 8KjQ== X-Forwarded-Encrypted: i=1; AJvYcCXteHhOX+omobOmUrn79+1sn5KO1y7MwJhajGt9nVmylF+WJ95rfWQDR/B6T1r1RyWHIeOifwGLN+RGN/6uoBmlT1SPWds= X-Gm-Message-State: AOJu0Yz93FVUlPhcogZ7ZveOKESrcoCh8U5QY1idFwO2w2Nc7SlVfTmC +yyzSkteawp5y/D2s23GrZi4BMxd3V6k79RKYuiMzyW4WybVuUf5 X-Google-Smtp-Source: AGHT+IG8ledTXUl0IDZBAqHjI2OfFBzfeL/4f3W2QpaICgJumHwDsuOA89YMgW/mABXln+9HXqbx5g== X-Received: by 2002:a62:b505:0:b0:6e3:3bd7:6f23 with SMTP id y5-20020a62b505000000b006e33bd76f23mr960762pfe.8.1708726184168; Fri, 23 Feb 2024 14:09:44 -0800 (PST) Received: from google.com ([2620:0:1000:8411:6da7:9880:a81c:aee8]) by smtp.gmail.com with ESMTPSA id a6-20020aa780c6000000b006e134c4d6b0sm13310100pfn.217.2024.02.23.14.09.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Feb 2024 14:09:43 -0800 (PST) Sender: Minchan Kim Date: Fri, 23 Feb 2024 14:09:41 -0800 From: Minchan Kim To: Barry Song <21cnbao@gmail.com> Cc: sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@suse.com, hannes@cmpxchg.org, Barry Song Subject: Re: [PATCH RFC] mm: madvise: pageout: ignore references rather than clearing young Message-ID: References: <20240223041550.77157-1-21cnbao@gmail.com> Precedence: bulk X-Mailing-List: damon@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: <20240223041550.77157-1-21cnbao@gmail.com> Hi Barry, On Fri, Feb 23, 2024 at 05:15:50PM +1300, Barry Song wrote: > From: Barry Song > > While doing MADV_PAGEOUT, the current code will clear PTE young > so that vmscan won't read young flags to allow the reclamation > of madvised folios to go ahead. Isn't it good to accelerate reclaiming? vmscan checks whether the page was accessed recenlty by the young bit from pte and if it is, it doesn't reclaim the page. Since we have cleared the young bit in pte in madvise_pageout, vmscan is likely to reclaim the page since it wouldn't see the ferencecd_ptes from folio_check_references. Could you clarify if I miss something here? > It seems we can do it by directly ignoring references, thus we > can remove tlb flush in madvise and rmap overhead in vmscan. > > Regarding the side effect, in the original code, if a parallel > thread runs side by side to access the madvised memory with the > thread doing madvise, folios will get a chance to be re-activated > by vmscan. But with the patch, they will still be reclaimed. But > this behaviour doing PAGEOUT and doing access at the same time is > quite silly like DoS. So probably, we don't need to care. > > A microbench as below has shown 6% decrement on the latency of > MADV_PAGEOUT, > > #define PGSIZE 4096 > main() > { > int i; > #define SIZE 512*1024*1024 > volatile long *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > > for (i = 0; i < SIZE/sizeof(long); i += PGSIZE / sizeof(long)) > p[i] = 0x11; > > madvise(p, SIZE, MADV_PAGEOUT); > } > > w/o patch w/ patch > root@10:~# time ./a.out root@10:~# time ./a.out > real 0m49.634s real 0m46.334s > user 0m0.637s user 0m0.648s > sys 0m47.434s sys 0m44.265s > > Signed-off-by: Barry Song > --- > mm/damon/paddr.c | 2 +- > mm/internal.h | 2 +- > mm/madvise.c | 8 ++++---- > mm/vmscan.c | 12 +++++++----- > 4 files changed, 13 insertions(+), 11 deletions(-) > > diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c > index 081e2a325778..5e6dc312072c 100644 > --- a/mm/damon/paddr.c > +++ b/mm/damon/paddr.c > @@ -249,7 +249,7 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s) > put_folio: > folio_put(folio); > } > - applied = reclaim_pages(&folio_list); > + applied = reclaim_pages(&folio_list, false); > cond_resched(); > return applied * PAGE_SIZE; > } > diff --git a/mm/internal.h b/mm/internal.h > index 93e229112045..36c11ea41f47 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -868,7 +868,7 @@ extern unsigned long __must_check vm_mmap_pgoff(struct file *, unsigned long, > unsigned long, unsigned long); > > extern void set_pageblock_order(void); > -unsigned long reclaim_pages(struct list_head *folio_list); > +unsigned long reclaim_pages(struct list_head *folio_list, bool ignore_references); > unsigned int reclaim_clean_pages_from_list(struct zone *zone, > struct list_head *folio_list); > /* The ALLOC_WMARK bits are used as an index to zone->watermark */ > diff --git a/mm/madvise.c b/mm/madvise.c > index abde3edb04f0..44a498c94158 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -386,7 +386,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > return 0; > } > > - if (pmd_young(orig_pmd)) { > + if (!pageout && pmd_young(orig_pmd)) { > pmdp_invalidate(vma, addr, pmd); > orig_pmd = pmd_mkold(orig_pmd); > > @@ -410,7 +410,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > huge_unlock: > spin_unlock(ptl); > if (pageout) > - reclaim_pages(&folio_list); > + reclaim_pages(&folio_list, true); > return 0; > } > > @@ -490,7 +490,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > > VM_BUG_ON_FOLIO(folio_test_large(folio), folio); > > - if (pte_young(ptent)) { > + if (!pageout && pte_young(ptent)) { > ptent = ptep_get_and_clear_full(mm, addr, pte, > tlb->fullmm); > ptent = pte_mkold(ptent); > @@ -524,7 +524,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > pte_unmap_unlock(start_pte, ptl); > } > if (pageout) > - reclaim_pages(&folio_list); > + reclaim_pages(&folio_list, true); > cond_resched(); > > return 0; > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 402c290fbf5a..ba2f37f46a73 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2102,7 +2102,8 @@ static void shrink_active_list(unsigned long nr_to_scan, > } > > static unsigned int reclaim_folio_list(struct list_head *folio_list, > - struct pglist_data *pgdat) > + struct pglist_data *pgdat, > + bool ignore_references) > { > struct reclaim_stat dummy_stat; > unsigned int nr_reclaimed; > @@ -2115,7 +2116,7 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list, > .no_demotion = 1, > }; > > - nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false); > + nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, ignore_references); > while (!list_empty(folio_list)) { > folio = lru_to_folio(folio_list); > list_del(&folio->lru); > @@ -2125,7 +2126,7 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list, > return nr_reclaimed; > } > > -unsigned long reclaim_pages(struct list_head *folio_list) > +unsigned long reclaim_pages(struct list_head *folio_list, bool ignore_references) > { > int nid; > unsigned int nr_reclaimed = 0; > @@ -2147,11 +2148,12 @@ unsigned long reclaim_pages(struct list_head *folio_list) > continue; > } > > - nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); > + nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid), > + ignore_references); > nid = folio_nid(lru_to_folio(folio_list)); > } while (!list_empty(folio_list)); > > - nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); > + nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid), ignore_references); > > memalloc_noreclaim_restore(noreclaim_flag); > > -- > 2.34.1 >