On Tue 28-05-19 11:04:46, Konstantin Khlebnikov wrote: > On 28.05.2019 10:38, Michal Hocko wrote: [...] > > Could you define the exact semantic? Ideally something for the manual > > page please? > > > > Like kswapd which works with thresholds of free memory this one reclaims > until 'free' (i.e. memory which could be allocated without invoking > direct recliam of any kind) is lower than passed 'size' argument. s@lower@higher@ I guess > Thus right after madvise(NULL, size, MADV_STOCKPILE) 'size' bytes > could be allocated in this memory cgroup without extra latency from > reclaimer if there is no other memory consumers. > > Reclaimed memory is simply put into free lists in common buddy allocator, > there is no reserves for particular task or cgroup. > > If overall memory allocation rate is smooth without rough spikes then > calling MADV_STOCKPILE in loop periodically provides enough room for > allocations and eliminates direct reclaim from all other tasks. > As a result this eliminates unpredictable delays caused by > direct reclaim in random places. OK, this makes it more clear to me. Thanks for the clarification! I have clearly misunderstood and misinterpreted target as the reclaim target rather than free memory target. Sorry about the confusion. I sill think that this looks like an abuse of the madvise but if there is a wider consensus this is acceptable I will not stand in the way. -- Michal Hocko SUSE Labs
