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b=jMtDExXefHWh9g0Ufr77FvXAmhFo7mMZG1sl1FdQCiaEls21Pt+1w+hADIokQdUqE 2Yd3N+tSItyZzwAiJAvu46jafblC9wTsKy/Jk3r6gFu1AhU9oCfSDxHkCIKKn302uI pH66J8UPU93wF/vQckjrcwVQP/O7O4WVCEqqZNgaDsVavzuXX/tX1IW9B3r78pF+mB 6R5spZT30/9MCLTwUirjviFHn4ZFddO1BR+Src4Pm0hU5iQhl/IDTrd3ijAJY/Gd/O XEH7S+FjG5E3+PJ1DOuZcMpiZJ749E22GR/SL/b56XrrffQrb4dkoUubpOLT6QCJH6 Wnuxfd+KuMMFg== From: SeongJae Park To: SeongJae Park Cc: damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: (sashiko review) [RFC PATCH v5 02/11] mm/damon/core: merge quota-sliced regions back Date: Sat, 11 Apr 2026 09:33:39 -0700 Message-ID: <20260411163340.46397-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260410235527.90900-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 66C2C4000F X-Stat-Signature: 3m8un9j3e3ac3aafo3cruqqk37pw144c X-Rspam-User: X-HE-Tag: 1775925234-830755 X-HE-Meta: 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 7WoN/90u C8b/i8VK+khLmq7U665TYyn0eTTIOC2clm4t9HRVp6h6kFlYts1Iip6khYAFKJ/mbiaOUCu6uVPosG8GFjBO9A8PuLIeBE5jATc0JN0marLS79A26S7O3uy4YIFx/X3NUtLqgutz1YpOhfIKbkO4vShM+inBU15qczNCUQnFDyFBDoNtkZc4ivyRjJAHePvEMCzZ5+Ig3EE9hzjsB2mglZ12Z6WxyUNag8DWu/kbHStzuRIwtCQL2SUl0qMWtyt2lkrDOx9ris1mXrVT87c7lvOGDRQ0zd9QOU7GgKnPH4v+U7TI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 10 Apr 2026 16:55:26 -0700 SeongJae Park wrote: [...] > > Should the merge condition verify that the contiguous slices share identical > > state before merging, perhaps by checking if (orig_region->age != r->age)? > > Good finding. I was thinking the scheme will anyway be applied, once the > quota-split is happened. But I was wrong, since DAMOS core filter is applied > after the split operation. Also, age is not reset if the action is DAMOS_STAT. > > I will address this in the next revision, like below. > > ''' > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -2439,35 +2439,32 @@ static void damon_do_apply_schemes(struct damon_ctx *c, > > static void damos_apply_target(struct damon_ctx *c, struct damon_target *t) > { > - struct damon_region *r, *orig_region = NULL; > - unsigned long orig_end_addr; > + struct damon_region *r; > > damon_for_each_region(r, t) { > + struct damon_region *prev_r; > + > + damon_do_apply_schemes(c, t, r); > /* > - * damon_do_apply_schemes() could split the region for the > + * damon_do_apply_scheems() could split the region for the > * quota. Keeping the new slices is an overhead. Merge back > - * the slices into the original region if there is no reason to > - * keep those. > + * the slices into the previous region if it doesn't lose any > + * information. > */ > - if (!orig_region || orig_end_addr <= r->ar.start) { > - orig_region = r; > - orig_end_addr = r->ar.end; > - } > - damon_do_apply_schemes(c, t, r); > - if (r == orig_region) > + if (damon_first_region(t) == r) > continue; > - /* > - * If no scheme was applied to the sliced region, the age of > - * the slice ain't be reset. Don't merge that back. > - * Otherwise, the monitored information of the region is lost. > - */ > - if (r->age) { > - orig_region = NULL; > + prev_r = damon_prev_region(r); > + if (prev_r->ar.end != r->ar.start) > continue; > - } > - orig_region->ar.end = r->ar.end; > + if (prev_r->age != r->age) > + continue; > + if (prev_r->last_nr_accesses != r->last_nr_accesses) > + continue; > + if (prev_r->nr_accesses != r->nr_accesses) > + continue; > + prev_r->ar.end = r->ar.end; > damon_destroy_region(r, t); > - r = orig_region; > + r = prev_r; > } > } This could result in too aggressive merging, that can make the number of regions lower than the min_nr_regions. Actually this makes one of damo tests fail. I will fix this by using damon_region_sz_limit(). Thanks, SJ [...]