Thanks Michal!! On 11/16/2023 6:25 PM, Michal Hocko wrote: >> May be other way to look at that patch is comment is really not being >> reflected in the code. It says, " Limit the number reserved to 1 >> pageblock or roughly 1% of a zone.", but the current code is making it 2 >> pageblocks. So, for 4M block size, it is > 1%. >> >> A second patch, that I will post, like not reserving the high atomic >> page blocks on small systems -- But how to define the meaning of small >> systems is not sure. Instead will let the system administrators chose >> this through either: >> a) command line param, high_atomic_reserves=off, on by default -- >> Another knob, so admins may really not like this? >> b) CONFIG_HIGH_ATOMIC_RESERVES, which if not defined, will not reserve. > Please don't! I do not see any admin wanting to care about this at all. > It just takes a lot of understanding of internal MM stuff to make an > educated guess. This should really be auto-tuned. And as responded in > other reply my take would be to reserve a page block on if it doesn't > consume more than 1% of memory to preserve the existing behavior yet not > overconsume on small systems. This idea of auto tune, by reserving a pageblock only if it doesn't consume more than 1% of memory, seems cleaner to me. For a page block size of 4MB, this will turnout to be upto 400MB of RAM. If it is fine, I can post a patch with suggested-by: you. >
