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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: ECD0320003 X-Stat-Signature: fumhzb1w5hor1mtr3ch84sfdkmx4mrcf X-HE-Tag: 1780285824-591902 X-HE-Meta: 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 Lnzrw5qX FcYUXhyfXLoyM7ya8Yov4uqyWrEd0G3gzcnex584yuNHDtpKaYRoEZcHl9rc0tU4hHpmPhPSL2hd5+cNt4KWBGarq2pNOEwaCnMDjqxXMZg8Gu0jGcCq4zy1PJ0DWgOqml7xgPeKbVoxhKu+iiIBg2fpnBAS2OS4TUfsQG4+iVJQnCoJA4O58x4knafiLFaMUL3Baa5oZHSpZWoAxHeMw8YGaLh0q4HFHBguHNhoE4f2+FvXHb+6SZ1kF9pcKBi3wfM8vBiDjIhRU7cs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, May 30, 2026 at 11:21:12AM -0700, Nhat Pham wrote: > On Sat, May 30, 2026 at 10:51 AM Nhat Pham wrote: > > > > > > How expensive is it to add per-cpu caching for each device :( > > to clarify - a percpu_swap_cluster per si for every si. > > > > > ... or for each tier (assuming devices in each tier share the same > performance characteristics, and could be used interchangeably?). > > Basically: > > struct percpu_swap_cluster { > struct swap_info_struct *si[MAX_SWAPTIER][SWAP_NR_ORDERS]; > unsigned long offset[MAX_SWAPTIER][SWAP_NR_ORDERS]; > local_lock_t lock; > }; > > Seems like 4 is the default number of tier right? So the extra > overhead is just (nr cpu) * 10 * 3 * (sizeof(unsigned long) + > sizeof(*ptr)) or wev? I agree. I actually considered the idea of a tier-centric cache as well. You might remember that in the previous "per cgroup swap priority" patchset, I implemented per-cpu caches per priority, which is essentially the same as having them per tier. However, as you agreed in another thread, including this optimization right now might be a bit premature. If the core swap tier idea gets merged, I plan to explore this optimization further as follow-up work. Thanks Youngjun Park