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b=aWX7QdTLaC+S0H6Ng1DygEk8hmS2i8460t5UpswUYziik0EIIk6T5kajeGEuyzO9t shWZaaOLp9nAnZJme0ICAO2v676BOCmF0QnQIUlYb6EGcptDiaP7ApTSOUnWD48i3O sHs6dlXY/QpprjBusNRdCNr/1o6+yXA8cTXNYsflBjocttIjqsHs02tgNCoJX6Hi43 W/mm+3t9StyjRphQjTwS2AmnhEtb0G+0HrlavOvwZsOw38hO37nDYt2xnySmm/q/1B tumLgtcMotZUyNsSLuSwUYJ+bR9YaHNfSuGnet8einkUt6HMyO5Iwld9Kz8D0GiBLh NFfp+j2iMnB4w== From: SeongJae Park To: Usama Arif Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH] mm/damon: increment pa_stat damon address range by folio size Date: Mon, 13 Jan 2025 11:04:05 -0800 Message-Id: <20250113190405.6723-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <8892b42c-3363-4fdf-ad3c-4bbd2a0a801b@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: mmp81iw8ais56urc5e9bgafnqpo3k1ya X-Rspam-User: X-Rspamd-Queue-Id: DCF3140005 X-Rspamd-Server: rspam08 X-HE-Tag: 1736795049-67379 X-HE-Meta: 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 9hv13h2Z LDlTm062cjUVPM+NZ6IK43XU47iFfeMSppoR94l0ic/Mb5hfPghaKryifN5EDbtmvOtEhKP/2bR9kTwv7wLGRyoMLiV9D45B9sTrzw4XoxgHwKQ6N3GyT9DYRCz2Pbcmu/BDZ5kgI+uwElh6pqOxObfUb1eOUNk4Uh8RjVTzkVJM8tSx+/Xi/cSoKB+vBpKZNSJ81jX32V+WcAAhCzRF9BNTWHOxOg8jux7VP4KlrjzV2Gm75BHI191G92n8j38PAOOs0SQnkxZdh6Q+gVma6iY+QFA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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, 13 Jan 2025 18:53:32 +0000 Usama Arif wrote: > > > On 13/01/2025 18:43, SeongJae Park wrote: > > Hi Usama, > > > > > > Let's use "mm/damon/paddr: " prefix for the patch title, to be more consistent > > with others. > > > > On Mon, 13 Jan 2025 18:03:40 +0000 Usama Arif wrote: > > > >> This is to take into account for folios with size > 1 page. > >> Iterating at PAGE_SIZE increment would increment sz_filter_passed > >> multiple times for the same folio by folio_size, providing incorrect > >> stats. > > > > damon_get_folio() returns NULL if the page is a tail page. Hence I think it > > will not increment sz_filter_passed multiple times? > > ahh I didn't look at the definition of damon_get_folio! just assumed it will get > the folio irrespective of if its a tail page or not. Will change the commit message. > > Just curious if returning NULL is what is expected by the user? > I see damon_get_folio used in a bunch a places. If the user limits damos action/ > damon monitoring to a specific address range, and that covers some of the tail pages, > but not the head page, I guess the damos action wont be applied. Yes, I think damon_get_folio() users (mostly DAMON operations set layer) should aware that and use different functions if it can be a problem, depending on each case. I find no problematic use cases of the function off the top of my head, but if you find, please help us fixing those :) [...] > >> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c > >> index 6b4397de4199..cc789a97c6f5 100644 > >> --- a/mm/damon/paddr.c > >> +++ b/mm/damon/paddr.c > >> @@ -504,7 +504,8 @@ static unsigned long damon_pa_stat(struct damon_region *r, struct damos *s, > >> if (!damon_pa_scheme_has_filter(s)) > >> return 0; > >> > >> - for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) { > >> + addr = r->ar.start; > >> + while (addr < r->ar.end) { > >> struct folio *folio = damon_get_folio(PHYS_PFN(addr)); > >> > >> if (!folio) > > > > In this case, the code does "continue". 'addr' is not advanced, so it will > > result in an infinite loop. Let's do 'addr += PAGE_SIZE' here, to avoid that. > > Thanks! Will fix this in v2. Nice, looking forward to it! Thanks, SJ [...]