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b=icvaP+T4vL8lB7rJAw7kuQPyoy5Z1d0qfqLK91Eo1y66kRKHm3r+iIv5nKlb0jqRc e8nWOD/9qE/pg4F7owoaH12r9daoQsAonOsUODrhb8+jnFbzwddfin86cks4REEmgh BbAvtx45d35WCYkxgwhZFvMtHikQu1uPOSqhpOlTRgNI1K+ptA8/nHWsMblAwz/+LQ lshJ3rm04YvFl4pi3t6rVyFFw5Hv8V0yT6l3A4hy71mxtKzOEUlXNIDQAAb0fHN5Bw nlbjmgCPwxnsKrGsbtjNPvVSXMax6XBdt6RsxcWXSO6jOM/gBEcpBZVsNeuddo4OcI w9gF+kZDN2Dpw== From: SeongJae Park To: Barry Song <21cnbao@gmail.com> Cc: SeongJae Park , Minchan Kim , 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 Date: Sat, 24 Feb 2024 12:54:52 -0800 Message-Id: <20240224205453.47096-1-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 630B5100005 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: umqsmxwa8o6uy57qijhhrzhjjn5p3jw9 X-HE-Tag: 1708808100-3726 X-HE-Meta: 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 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 Sun, 25 Feb 2024 04:01:40 +0800 Barry Song <21cnbao@gmail.com> wrote: > On Sun, Feb 25, 2024 at 3:07 AM SeongJae Park wrote: > > > > Hi Barry, > > > > On Sat, 24 Feb 2024 12:37:59 +0800 Barry Song <21cnbao@gmail.com> wrote: > > > > [...] > > > > > > BTW， > > > Hi SeongJae, > > > I am not quite sure if damon also needs this, so I have kept damon as is by > > > setting ignore_references = false. MADV_PAGEOUT is an explicit hint users > > > don't want the memory to be reclaimed, I don't know if it is true for damon as > > > well. If you have some comments, please chime in. > > > > Thank you for calling my name :) > > > > For DAMON's usecase, the document simply says the behavior would be same to > > MADV_PAGEOUT, so if we conclude to change MADV_PAGEOUT, I think same change > > should be made for DAMON's usecase, or update DAMON document. > > Hi SeongJae, > > I don't find similar clearing pte young in damon_pa_pageout(), so i > guess damon's > behaviour is actually different with MADV_PAGEOUT which has pte-clearing. damon > is probably the best-effort but MADV_PAGEOUT isn't . > > static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s) > { > unsigned long addr, applied; > LIST_HEAD(folio_list); > > for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) { > struct folio *folio = damon_get_folio(PHYS_PFN(addr)); > .... > > if (damos_pa_filter_out(s, folio)) > goto put_folio; > > folio_clear_referenced(folio); > folio_test_clear_young(folio); > if (!folio_isolate_lru(folio)) > goto put_folio; > if (folio_test_unevictable(folio)) > folio_putback_lru(folio); > else > list_add(&folio->lru, &folio_list); > put_folio: > folio_put(folio); > } > applied = reclaim_pages(&folio_list); > cond_resched(); > return applied * PAGE_SIZE; > } > > am i missing something? Thank you for checking this again. You're right. Technically speaking, DAMON's usage of MADV_PAGEOUT is in vaddr.c. paddr.c is using not MADV_PAGEOUT but reclaim_pages(). Usage of reclaim_pages() from paddr is different from that of MADV_PAGEOUT since paddr doesn't clear PTE. I was confused from the difference between vaddr and paddr. I actually wanted to document the difference but haven't had a time for that yet. Thank you for letting me remind this. So, your change on MADV_PAGEOUT will make an effect to vaddr, and I think it's ok. Your change on reclaim_pages() could make an effect to paddr, depending on the additional parameter's value. I now think it would better to make no effect here. That is, let's keep the change for paddr.c in your patch as is. Thanks, SJ > > > > > > > Thanks, > > SJ > > > > Thanks > Barry