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 5A8841DFE5; Sat, 24 Feb 2024 20:54:56 +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=1708808096; cv=none; b=W4mqbH1tKPNfgg3dld7cQOOM3BGAfrPVz/llMjhVApvj9DpKMx4ZqBkJbzr9b9sOMYHkM6yvp9jwARJQFM2WocaXkIv1Fjv0Wclvmp12RDz7cEpGBu5cBaTCp6mkRk8SJFMBfWlYAm6GkPYAa8PNofOehV+1m9o4KXll2kYAMLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708808096; c=relaxed/simple; bh=sAzkLyInW8vnZNRVOTYLy2onbr1cozPVspALWkhdV+M=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=dUvWbrojvN36DS2lJAB6nnwskjK8g6VqrHtWc5GFg5VUf8W4jzLY+TGAhYk2fug2f7qTt8vhiEJnFZClbXrnQwQ7i0LwrHb8z/3syV603McdIROzDCkVsH2TeDFhhw9ul0q7lONX4WHNuxFJx7vN2IVd6OGuWEnEm//nNQRUjIA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=icvaP+T4; 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="icvaP+T4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07E17C433C7; Sat, 24 Feb 2024 20:54:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708808095; bh=sAzkLyInW8vnZNRVOTYLy2onbr1cozPVspALWkhdV+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; 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: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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