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b=zXfSSqJDBv/TS/85VIqvKEzx4cv9xKXT47IrBBPNUimtYz6xCt4upu/nj38G9cBVh QgDLimptmLVFuO+2BCah/6B3M3fHbNMMmqEa+IBcXYb6QO9lIxyPj05bzOySaKO35z e2/QtZ+PLuUF86hpa/9xxdHs7CagDh602Zm4ULqs= Date: Wed, 9 Oct 2024 13:49:00 -0700 From: Andrew Morton To: Jaewon Kim Cc: sj@kernel.org, minchan@kernel.org, vbabka@suse.cz, kaleshsingh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com Subject: Re: [PATCH] vmscan: add a vmscan event for reclaim_pages Message-Id: <20241009134900.7cd8fe9000a9fafd7ca1c592@linux-foundation.org> In-Reply-To: <20241009093124.3647359-1-jaewon31.kim@samsung.com> References: <20241009093124.3647359-1-jaewon31.kim@samsung.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 1k4a7ab5g9tbrh745fd4u4e1zoz36e9r X-Rspamd-Queue-Id: 2C93C1C0013 X-Rspamd-Server: rspam02 X-HE-Tag: 1728506941-550628 X-HE-Meta: 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 WdqthI46 nH+BxmZ71+vFBQeD/zeRxkT8s60kdxaqJZ0xA8LlpHBdJQYlYoq2yH+R9dSnsCZdI+zDJxvTscSQATVXVUkJffxGf3Fk5h4X3UJmGJkegGhnseBCjl4Z9B8ssjQ+DCqY95TaxJCYuvvu5f0/gXIt5fGteaE0coa20/RVPTm5+Ot0DHFAlC10l+towxq7NOO/75jP0pQW+Su8prwFq5eq2EM4l7PnBLbwl7Tz29p6TpmagIBTrBJ+JEEukoTYlyF1zv1NjBBfY4qqRar2OLzcbw8tcEL2Fyk/7tl0oQ462Jikz9Qg4FZI9GmTx+kIm9e7lvvcIsw+2fD46e8FBEIR2WnyUYQrURUaL0/+W62LWBoXYCG7g8UaaqTG2j4VedPUSRoz7Tr5rUSzm8Lg= 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 Wed, 9 Oct 2024 18:31:24 +0900 Jaewon Kim wrote: > The reclaim_folio_list uses a dummy reclaim_stat and is not being > used. To know the memory stat, add a new trace event. This is useful how > how many pages are not reclaimed or why. > > This is an example. > mm_vmscan_reclaim_pages: nr_scanned=17 nr_reclaimed=17 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 > > Currenlty reclaim_folio_list is only called by reclaim_pages, and > reclaim_pages is used by damon and madvise. In the latest Android, > reclaim_pages is also used by shmem to reclaim all pages in a > address_space. > This looks like it will add some overhead when tracing has been enabled. Has this been measured and is it significant? Also, we're adding a significant amount of code for a simple trace record. Do others think this is justifiable?