On Mon, Jul 03, 2023 at 07:36:41PM +0530, Charan Teja Kalla wrote: > A folio turns into a Workingset during: > 1) shrink_active_list() placing the folio from active to inactive list. > 2) When a workingset transition is happening during the folio refault. > > And when Workingset is set on a folio, PSI for memory can be accounted > during a) That folio is being reclaimed and b) Refault of that folio, > for usual reclaims. > > This accounting of PSI for memory is not consistent for reclaim + > refault operation between usual reclaim and madvise(COLD/PAGEOUT) which > deactivate or proactively reclaim a folio: > a) A folio started at inactive and moved to active as part of accesses. > Workingset is absent on the folio thus refault of it when reclaimed > through MADV_PAGEOUT operation doesn't account for PSI. > > b) When the same folio transition from inactive->active and then to > inactive through shrink_active_list(). Workingset is set on the folio > thus refault of it when reclaimed through MADV_PAGEOUT operation > accounts for PSI. > > c) When the same folio is part of active list directly as a result of > folio refault and this was a workingset folio prior to eviction. > Workingset is set on the folio thus the refault of it when reclaimed > through MADV_PAGEOUT/MADV_COLD operation accounts for PSI. > > d) MADV_COLD transfers the folio from active list to inactive > list. Such folios may not have the Workingset thus refault operation on > such folio doesn't account for PSI. > > As said above, refault operation caused because of MADV_PAGEOUT on a > folio is accounts for memory PSI in b) and c) but not in a). Refault > caused by the reclaim of a folio on which MADV_COLD is performed > accounts memory PSI in c) but not in d). These behaviours are > inconsistent w.r.t usual reclaim + refault operation. Make this PSI > accounting always consistent by turning a folio into a workingset one > whenever it is leaving the active list. Also, accounting of PSI on a > folio whenever it leaves the active list as part of the > MADV_COLD/PAGEOUT operation helps the users whether they are operating > on proper folios[1]. > > [1] https://lore.kernel.org/all/20230605180013.GD221380@xxxxxxxxxxx/ > > Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > Reported-by: Sai Manobhiram Manapragada <quic_smanapra@xxxxxxxxxxx> > Reported-by: Pavan Kondeti <quic_pkondeti@xxxxxxxxxxx> > Signed-off-by: Charan Teja Kalla <quic_charante@xxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Thanks Charan
