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SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_SEVEN(0.00)[10]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spam-Level: X-Rspamd-Action: no action X-Rspamd-Queue-Id: 4FC705BCCD X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO On 1/13/26 08:13, Yajun Deng wrote: > January 12, 2026 at 10:50 PM, "Johannes Weiner" wrote: > > >> >> On Mon, Jan 12, 2026 at 08:16:14PM +0800, Yajun Deng wrote: >> >> > >> > In move_to_free_list(), when a page block changes its migration type, >> > we need to update free page counts for both the old and new types. >> > Originally, this was done by two calls to account_freepages(), which >> > updates NR_FREE_PAGES and also type-specific counters. However, this >> > causes NR_FREE_PAGES to be updated twice, while the net change is zero >> > in most cases. >> > >> > This patch adds a condition that updates the NR_FREE_PAGES only if one of >> > the two types is the isolate type. This avoids NR_FREE_PAGES being >> > updates twice. >> > >> > The optimization avoid duplicate NR_FREE_PAGES updates in >> > move_to_free_list(). >> > >> > Signed-off-by: Yajun Deng >> > Suggested-by: Joshua Hahn >> > >> I'm not a fan of this. >> >> The code ends up more complicated, more lines, and fragile because the >> accounting decisions are now spread out over multiple places (again). Agreed. >> > How about V1? It will introduce account_freepages_both(). > https://lore.kernel.org/all/20260109105121.328780-1-yajun.deng@linux.dev/ Also not a fan myself. Thanks, Vlastimil >> Is it worth it? move_to_free_list() is used in page isolation, which >> has to do the accounting anyway; and migratetype fallbacks, which we >> are trying to avoid as much as possible. So this path shouldn't be all >> that hot to begin with. >> > Not all cases are of the isolation type. There are indeed duplicate caculations. > move_freepages_block() will be called in __isolate_free_page(). > Both old_mt and new_mt are mergeable type in this case. > >> Simplicity & maintainability trumps here, IMO, unless you have hard >> data showing this is worth the pain. >> > I'm tring to do it, but I haven't yet.