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charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20231206110054.61617-1-v-songbaohua@oppo.com> X-Rspam-User: X-Stat-Signature: mrb8rhuewxnoru5g7rz571m57fts8c6e X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E004940016 X-HE-Tag: 1702472555-494577 X-HE-Meta: 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 fSb1mKEC KpDWBYdzTnBPoROu4n5ODVjyg0M3WTdmiCKtqV9V7WIoc3Taltp3pWS7GeJ/H/GbmDe4dNEbuy12TY2hngS6UN5YtvFgwRzVtcbzIYYmIl1HzYwMXSsW23vRxdypvDih3yEvEEIkNd1nfBGaZj6bbPDvUaqEYdKdDWpE7HfXqdpTwO8ciazKBSKL+dEigIWbgqJkxcdIwmbkDC4nDC3gNEQWng3efS5BpgY/2ei0sKLSlJbzToi/lDqqdb6tnpJe4SGSwRNts3L3Vtn+zWBEJhpiDDs11KzL+UPyS0jlKRl9MclnK7st01/K+eXlnTB2nLOQr6/MMvJBY5QX31nkKz8RDwg== 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 Thu, Dec 07, 2023 at 12:00:54AM +1300, Barry Song wrote: > Testing shows fast_isolate_freepages can blindly choose an unsuitable > pageblock from time to time particularly while the min mark is used > from XXX path: > if (!page) { > cc->fast_search_fail++; > if (scan_start) { > /* > * Use the highest PFN found above min. If one was > * not found, be pessimistic for direct compaction > * and use the min mark. > */ > if (highest >= min_pfn) { > page = pfn_to_page(highest); > cc->free_pfn = highest; > } else { > if (cc->direct_compaction && pfn_valid(min_pfn)) { /* XXX */ > page = pageblock_pfn_to_page(min_pfn, > min(pageblock_end_pfn(min_pfn), > zone_end_pfn(cc->zone)), > cc->zone); > cc->free_pfn = min_pfn; > } > } > } > } > > The reason is that no code is doing any check on the min_pfn > min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1)); > > In contrast, slow path of isolate_freepages() is always skipping unsuitable > pageblocks in a decent way. > > This issue doesn't happen quite often. When running 25 machines with 16GiB > memory for one night, most of them can hit this unexpected code path. > However the frequency isn't like many times per second. It might be one > time in a couple of hours. Thus, it is very hard to measure the visible > performance impact in my machines though the affection of choosing the > unsuitable migration_target should be negative in theory. > > I feel it's still worth fixing this to at least make the code theoretically > self-explanatory as it is quite odd an unsuitable migration_target can be > still migration_target. > > Reported-by: Zhanyuan Hu > Signed-off-by: Barry Song Acked-by: Mel Gorman -- Mel Gorman SUSE Labs