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Wed, 05 Nov 2025 05:34:19 -0800 (PST) Date: Wed, 5 Nov 2025 10:32:23 -0300 From: Pedro Demarchi Gomes To: "David Hildenbrand (Red Hat)" Cc: David Hildenbrand , Andrew Morton , Xu Xin , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] ksm: perform a range-walk in break_ksm Message-ID: References: <20251031174625.127417-1-pedrodemargomes@gmail.com> <20251031174625.127417-3-pedrodemargomes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 98msjzeqztr4mywsjmo5m51m78wrtfbs X-Rspam-User: X-Rspamd-Queue-Id: 928C11C0005 X-Rspamd-Server: rspam10 X-HE-Tag: 1762349660-549814 X-HE-Meta: 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 6+HZxAYp sWnAwmULRPLAxjIrVpzucgHi23fDN2+OW1v6oPlYFQkH50fPAltVVRD37MQ== 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: List-Subscribe: List-Unsubscribe: On Mon, Nov 03, 2025 at 06:06:26PM +0100, David Hildenbrand (Red Hat) wrote: > On 31.10.25 18:46, Pedro Demarchi Gomes wrote: > > Make break_ksm() receive an address range and change > > break_ksm_pmd_entry() to perform a range-walk and return the address of > > the first ksm page found. > > > > This change allows break_ksm() to skip unmapped regions instead of > > iterating every page address. When unmerging large sparse VMAs, this > > significantly reduces runtime. > > > > In a benchmark unmerging a 32 TiB sparse virtual address space where > > only one page was populated, the runtime dropped from 9 minutes to less > > then 5 seconds. > > > > Suggested-by: David Hildenbrand > > Signed-off-by: Pedro Demarchi Gomes > > --- > > mm/ksm.c | 88 ++++++++++++++++++++++++++++++-------------------------- > > 1 file changed, 48 insertions(+), 40 deletions(-) > > > > diff --git a/mm/ksm.c b/mm/ksm.c > > index 922d2936e206..64d66699133d 100644 > > --- a/mm/ksm.c > > +++ b/mm/ksm.c > > @@ -607,35 +607,55 @@ static inline bool ksm_test_exit(struct mm_struct *mm) > > return atomic_read(&mm->mm_users) == 0; > > } > > -static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long next, > > +struct break_ksm_arg { > > + unsigned long addr; > > +}; > > Leftover? :) > Yes, I am sorry. I will remove it in the v3. > > + > > +static int break_ksm_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, > > struct mm_walk *walk) > > { > > - struct folio *folio = NULL; > > + unsigned long *found_addr = (unsigned long *) walk->private; > > + struct mm_struct *mm = walk->mm; > > + pte_t *start_ptep, *ptep; > > spinlock_t *ptl; > > - pte_t *pte; > > - pte_t ptent; > > - int ret; > > + int found = 0; > > Best to perform the ret -> found rename already in patch #1. > Ok > With both things > > Acked-by: David Hildenbrand (Red Hat) Thanks! > -- > Cheers > > David >