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 4gOpldxB kGL+0gNykZdVy+qtcr1qMH25vta+0lyKIOXs8/nqpNNpkgSw8dEsrdsjHEHNheB8kQAKHsAsWOWY5tRmMqEywk/pOlHotUTioLIyiNVzFSG1Fmjs3fntGC9UB8dL+ifeNPz+pZdf3KQUc4pVoL7X/RzEIJrBzs5bYGX5tCPkXbWCjdDwGQQwC2OKwOF/rM0HVVLukgkEHnxcBHI3I15b0MjaCi1KrnBh/TeCZ1nWqF/oPLIuFBMJyOOcfpQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2023/11/29 23:17, Matthew Wilcox 写道: > On Wed, Nov 29, 2023 at 09:01:26PM +0800, Zhiguo Jiang wrote: >> It is needed to ensure sc->nr.unqueued_dirty > 0, which can avoid to >> set PGDAT_DIRTY flag when sc->nr.unqueued_dirty and sc->nr.file_taken >> are both zero at the same time. > Have you observed this happening, or is this from code review? Found in code review. The other sc->nr parameters are also judged whether they themselves are zero first in shrink_node. > >> It can't be guaranteed for the PGDAT_WRITEBACK flag that only pages >> marked for immediate reclaim are on evictable LRUs in other following >> shrink processes of the same kswapd shrink recycling. So when both a >> small amount of pages marked for immediate reclaim and a large amount >> of pages marked for non-immediate reclaim are on evictable LRUs at the >> same time, if it's only determined that there is at least a page marked >> for immediate reclaim on evictable LRUs, kswapd shrink is throttled to >> sleep, which will increase kswapd process consumption. >> >> It can be fixed to throttle kswapd shrink when sc->nr.immediate is equal >> to sc->nr.file_taken. > So you're fixing two distinct things in the same patch? It can be understood as two issues, and I will submit them separately. > >> +++ b/mm/vmscan.c >> @@ -5915,17 +5915,17 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) >> set_bit(PGDAT_WRITEBACK, &pgdat->flags); >> >> /* Allow kswapd to start writing pages during reclaim.*/ >> - if (sc->nr.unqueued_dirty == sc->nr.file_taken) >> + if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty == sc->nr.file_taken) >> set_bit(PGDAT_DIRTY, &pgdat->flags); >> >> /* >> - * If kswapd scans pages marked for immediate >> + * If kswapd scans massive pages marked for immediate > I don't understand why you've added the word "massive". Do you mean > that the pages are large, or that kswapd has scanned a lot of pages? The added "massive" means that there are a large number of pages marked for immediate reclaim on evictable LRUs. The added "massive" is relative to the situation that there is only a small amount of pages marked for immediate reclaim or even only one page marked for immediate reclaim on the evictable LRUs for throttle kswapd, and I think this situation don't need to throttle, because there may be other types of pages on evictable LRUs. > >> * reclaim and under writeback (nr_immediate), it >> * implies that pages are cycling through the LRU >> * faster than they are written so forcibly stall >> * until some pages complete writeback. >> */ >> - if (sc->nr.immediate) >> + if (sc->nr.immediate && sc->nr.immediate == sc->nr.file_taken) >> reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); >> }