From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98FEABE4E; Tue, 29 Jul 2025 18:15:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753812914; cv=none; b=Z+XAgnjcDfQY7KG3ws/uVyvJBBMnZ4QT+tV8zUMCODVQqjjnSBDVNPob0RHfTVRHrWDpqDnEzBmuhbuGvj09vm3sleT8WEzpGavZAcj1M+dvoS0ZzcNysLhy1txIbXj1iywLBUMctmmI7fM8CXeeDaQiTPaM0Yj3/SW7QZdEyZc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753812914; c=relaxed/simple; bh=TZBXNASe2pDArkZUxLGfDiu3sHbEqjRKTJxrS5ouBFc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=J8Lkdq9p+aGGg+rIT0VXXyCn/wlGmVvnkKsI6lf3flyV9v8eW3gLwSuZrRLcKDNEHMz/zQLiXpyMEAMI2YEKX7Ll6fDo2A9uBV88AE8HFKIJbxrYNgxwxqejHrbsaf/f3GUfD0c+rQSGWl9fzIfQi1BNjjkzg+6IUmFHsHB4USQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H4vtOIB5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="H4vtOIB5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00DF3C4CEEF; Tue, 29 Jul 2025 18:15:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753812914; bh=TZBXNASe2pDArkZUxLGfDiu3sHbEqjRKTJxrS5ouBFc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H4vtOIB5goB0G2wlEpeI5Fr7i+EoWJ8c2jyBLUs/g4xSJrX7T5EDUNm/GeORWt8lN O6QZ1bzxPmee+Kyx0SCq6Yn0fCBdqimJL99tm9FG+TIqWijEPg4N5yNIOdabvM/RkR 8Mg40E7YPj8cMkto4MLdbB7oWrJfKbGekJwUPEp38Zkxly9g8mOb094yEdGTy3B+ef F0HmC4djkXyrHOfqFbZtrv3Rv2qCHtlcTC1YVlzlP3B505aWU49bxMMuYJ2mZfORBn yBPv4yLzzCnQjtUl4sOr78vy2soY3fdtb2MgdJKYxBzGdxiGhEl4laSs7DOZrUEBXr pw7CGR7wAtTYw== From: SeongJae Park To: Yueyang Pan Cc: SeongJae Park , Andrew Morton , Usama Arif , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] mm/damon: Add damos_stat support for vaddr Date: Tue, 29 Jul 2025 11:15:10 -0700 Message-Id: <20250729181510.56035-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <44a30f700fdcf4470318ef5cd248ba98c59b77a2.1753794408.git.pyyjason@gmail.com> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 29 Jul 2025 06:53:30 -0700 Yueyang Pan wrote: > From: PanJason > > This patch adds support for damos_stat in virtual address space. > It leverages the walk_page_range to walk the page table and gets > the folio from page table. The last folio scanned is stored in > damos->last_applied to prevent double counting. Thank you for this patch, Pan! I left a few comments below. I think those are mostly insignificant change requests, though. > --- > mm/damon/vaddr.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 112 insertions(+), 1 deletion(-) > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > index 87e825349bdf..3e319b51cfd4 100644 > --- a/mm/damon/vaddr.c > +++ b/mm/damon/vaddr.c > @@ -890,6 +890,117 @@ static unsigned long damos_va_migrate(struct damon_target *target, > return applied * PAGE_SIZE; > } > > +struct damos_va_stat_private { > + struct damos *scheme; > + unsigned long *sz_filter_passed; > +}; > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct damos_va_stat_private *priv = walk->private; > + struct damos *s = priv->scheme; > + unsigned long *sz_filter_passed = priv->sz_filter_passed; > + struct folio *folio; > + spinlock_t *ptl; > + pmd_t pmde; > + > + ptl = pmd_lock(walk->mm, pmd); > + pmde = pmdp_get(pmd); > + > + if (!pmd_present(pmde) || !pmd_trans_huge(pmde)) > + goto unlock; > + > + /* Tell page walk code to not split the PMD */ > + walk->action = ACTION_CONTINUE; As David suggested, let's unify this with pte handler following the pattern of madvise_cold_or_pageout_pte_range() and drop above ACTION_CONTINUE code, unless you have different opinions. > + > + folio = damon_get_folio(pmd_pfn(pmde)); As also David suggested, let's use vm_normal_folio_pmd() instead, and drop unnecessary folio_put(). > + if (!folio) > + goto unlock; damon_invalid_damos_folio() returns true if folio is NULL, so I think above check is unnecessary. > + > + if (damon_invalid_damos_folio(folio, s)) > + goto update_last_applied; Because we didn't really apply the DAMOS action, I think it is more proper to goto 'unlock' directly. Oh, and I now realize damon_invalid_damos_folio() puts the folio for none-NULL invalid folio... Because the code is simple, let's implement and use 'va' version invalid_damos_folio(), say, damon_va_invalid_damos_folio(), which doesn't put the folio. > + > + if (!damos_va_filter_out(s, folio, walk->vma, addr, NULL, pmd)){ > + *sz_filter_passed += folio_size(folio); > + } Let's remove braces for single statement, as suggested[1] by the coding style. > + > + folio_put(folio); > +update_last_applied: > + s->last_applied = folio; > +unlock: > + spin_unlock(ptl); > + return 0; > +} > +#else > +#define damon_va_stat_pmd_entry NULL > +#endif > + > +static int damos_va_stat_pte_entry(pte_t *pte, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct damos_va_stat_private *priv = walk->private; > + struct damos *s = priv->scheme; > + unsigned long *sz_filter_passed = priv->sz_filter_passed; > + struct folio *folio; > + pte_t ptent; > + > + ptent = ptep_get(pte); > + if (pte_none(ptent) || !pte_present(ptent)) > + return 0; > + > + folio = damon_get_folio(pte_pfn(ptent)); As David suggested, let's use vm_normal_folio() here, and remove below folio_put(). > + if (!folio) > + return 0; As also mentioned above, let's drop above NULL case check, in favor of that in damon_va_invalid_damos_folio(). > + > + if (damon_invalid_damos_folio(folio, s)) > + goto update_last_applied; Again, I don't think we need to update s->last_applied in this case. Let's do only necessary cleanups and return. > + > + if (!damos_va_filter_out(s, folio, walk->vma, addr, pte, NULL)){ > + *sz_filter_passed += folio_size(folio); > + } Let's drop braces for single statement[1]. > + > + folio_put(folio); > + > +update_last_applied: > + s->last_applied = folio; > + return 0; > +} > + > +static unsigned long damos_va_stat(struct damon_target *target, > + struct damon_region *r, struct damos *s, > + unsigned long *sz_filter_passed) > +{ > + Let's remove this unnecessary blank line. > + struct damos_va_stat_private priv; > + struct mm_struct *mm; > + struct mm_walk_ops walk_ops = { > + .pmd_entry = damos_va_stat_pmd_entry, > + .pte_entry = damos_va_stat_pte_entry, > + .walk_lock = PGWALK_RDLOCK, > + }; > + > + priv.scheme = s; > + priv.sz_filter_passed = sz_filter_passed; > + > + if (!damon_scheme_has_filter(s)){ > + return 0; > + } Let's remove braces for single statement[1]. > + > + mm = damon_get_mm(target); > + if (!mm) > + return 0; > + > + mmap_read_lock(mm); > + walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv); > + mmap_read_unlock(mm); > + mmput(mm); > + pr_debug("Call va_stat: %lu\n", *sz_filter_passed); I don't think we really need this debug log. Can we remove? > + return 0; > + Yet another unnecessary blank line. Let's remove. > +} > + > static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx, > struct damon_target *t, struct damon_region *r, > struct damos *scheme, unsigned long *sz_filter_passed) > @@ -916,7 +1027,7 @@ static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx, > case DAMOS_MIGRATE_COLD: > return damos_va_migrate(t, r, scheme, sz_filter_passed); > case DAMOS_STAT: > - return 0; > + return damos_va_stat(t, r, scheme, sz_filter_passed); > default: > /* > * DAMOS actions that are not yet supported by 'vaddr'. > -- > 2.47.3 [1] https://docs.kernel.org/process/coding-style.html Thanks, SJ