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imf28.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf28.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707789798; a=rsa-sha256; cv=none; b=YSgdksMlfNOwMtdUKPytgEONBgF2tPLbrG82Y4DRK0Y9iUlEbgck/Ih2ame+xDeOY3MA2r ioCTbyWjsTVdNrstL5Zp9sNH35CWcr51Phr79/9DT0sqEEnJYK+D6VNkimdY5Uqozg+Nts cb8HR8vp74rLYDfU9pXPpyq5NdQmwsM= X-AuditID: a67dfc5b-d85ff70000001748-87-65cacde0032d Date: Tue, 13 Feb 2024 11:03:07 +0900 From: Byungchul Park To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, ying.huang@intel.com, namit@vmware.com, vernhao@tencent.com, mgorman@techsingularity.net, hughd@google.com, willy@infradead.org, david@redhat.com, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, rjgolo@gmail.com Subject: Re: [RESEND PATCH v7 6/8] mm: Add APIs to free a folio directly to the buddy bypassing pcp Message-ID: <20240213020307.GC4147@system.software.com> References: <20240208062608.44351-1-byungchul@sk.com> <20240208062608.44351-7-byungchul@sk.com> <20240208124919.a0e1707fefc29c2f4213e509@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; 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The folios freed by > > migrc are too old to keep in pcp. > > How do we define "too old" and what causes you to believe this is the case? Migrc defers folio_put() for source folios of migration that would be unlikely used and frees a bunch of folios at once later. However, it pollutes pcp, which means fresher folios might get free_pcppages_bulk()ed and makes the effort to keep the best amount of pcp get unstable. So I didn't want to make this situation happen. Byungchul