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dkim=pass header.d=gmail.com header.s=20210112 header.b=OQ4OIy9G; spf=pass (imf16.hostedemail.com: domain of xiakaixu1987@gmail.com designates 209.85.128.46 as permitted sender) smtp.mailfrom=xiakaixu1987@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam12 X-HE-Tag: 1663143709-395488 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: On Wed, Sep 14, 2022 at 4:04 PM SeongJae Park wrote: > > On Wed, 14 Sep 2022 12:02:05 +0800 Kaixu Xia wrote: > > > On Tue, Sep 13, 2022 at 11:11 PM SeongJae Park wrote: > > > > > > On Tue, 13 Sep 2022 17:11:27 +0800 xiakaixu1987@gmail.com wrote: > > > > > > > From: Kaixu Xia > > > > > > > > When 'init()' and 'update()' DAMON operations failed and the number > > > > of the damon_target regions is zero, > > > > > > Well, I think that could be a temporal failure. In the case, later call of > > > 'update()' could success? > > > > > Yeah, the kdamond while() loop calls 'update()' periodically to fix this > > temporary failure. But for extreme scenarios that 'update()' continues to fail, > > we should have some ways to detect this case. > > Even in the case, kdamond will do nothing but continuing the main loop while > sleeping sample_aggr interval (5ms by default) for each iteration, and calling > 'update()' for every update interval (100ms by default). Waste is waste, but I > don't think that's a real issue. Further, continuous 'update()' failures mean > the process is in some weird state anyway, so I'd assume the process would be > finished soon. kdamond will also finish as soon as the process finishes. > Users could also find the strange situation (nothing in the monitoring results) > and finish kdamond on their own. > > Anything I'm missing? > That sounds reasonable. Thanks for your detailed explanation. Thanks, Kaixu > > Andrew, I found you merged this patch in mm-unstable. Could you please hold it > until we finish this discussion? > > > Thanks, > SJ > > > > > Thanks, > > Kaixu > > > > > > Thanks, > > > SJ > > > > > > > the kdamond would do nothing > > > > to this monitoring target in this case. It makes no sense to run > > > > kdamond when all of monitoring targets have no regions. So add the > > > > judgement in 'target_valid()' operation to indicate the target is > > > > invalid when 'nr_regions' is zero. > > > > > > > > > > > Signed-off-by: Kaixu Xia > > > > --- > > > > mm/damon/vaddr.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > > > > index 39ea48d9cc15..65ff98d49ec0 100644 > > > > --- a/mm/damon/vaddr.c > > > > +++ b/mm/damon/vaddr.c > > > > @@ -598,6 +598,9 @@ static bool damon_va_target_valid(void *target) > > > > struct damon_target *t = target; > > > > struct task_struct *task; > > > > > > > > + if (!damon_nr_regions(t)) > > > > + return false; > > > > + > > > > task = damon_get_task_struct(t); > > > > if (task) { > > > > put_task_struct(task); > > > > -- > > > > 2.27.0 > >