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charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B80BD4000B X-Stat-Signature: gkq9s6se3hifc14bd9jspa591pq5pqm7 X-Rspam-User: X-HE-Tag: 1717019998-712966 X-HE-Meta: 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 vvCTsfAC 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 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 Wed, May 29, 2024, Yu Zhao wrote: > On Wed, May 29, 2024 at 12:05=E2=80=AFPM James Houghton wrote: > > > > Secondary MMUs are currently consulted for access/age information at > > eviction time, but before then, we don't get accurate age information. > > That is, pages that are mostly accessed through a secondary MMU (like > > guest memory, used by KVM) will always just proceed down to the oldest > > generation, and then at eviction time, if KVM reports the page to be > > young, the page will be activated/promoted back to the youngest > > generation. >=20 > Correct, and as I explained offline, this is the only reasonable > behavior if we can't locklessly walk secondary MMUs. >=20 > Just for the record, the (crude) analogy I used was: > Imagine a large room with many bills ($1, $5, $10, ...) on the floor, > but you are only allowed to pick up 10 of them (and put them in your > pocket). A smart move would be to survey the room *first and then* > pick up the largest ones. But if you are carrying a 500 lbs backpack, > you would just want to pick up whichever that's in front of you rather > than walk the entire room. >=20 > MGLRU should only scan (or lookaround) secondary MMUs if it can be > done lockless. Otherwise, it should just fall back to the existing > approach, which existed in previous versions but is removed in this > version. IIUC, by "existing approach" you mean completely ignore secondary MMUs that= don't implement a lockless walk?