* Christoph Lameter <cl@xxxxxxxxx> [2011-01-21 09:55:17]: > On Fri, 21 Jan 2011, Balbir Singh wrote: > > > * Christoph Lameter <cl@xxxxxxxxx> [2011-01-20 09:00:09]: > > > > > On Thu, 20 Jan 2011, Balbir Singh wrote: > > > > > > > + unmapped_page_control > > > > + [KNL] Available if CONFIG_UNMAPPED_PAGECACHE_CONTROL > > > > + is enabled. It controls the amount of unmapped memory > > > > + that is present in the system. This boot option plus > > > > + vm.min_unmapped_ratio (sysctl) provide granular control > > > > > > min_unmapped_ratio is there to guarantee that zone reclaim does not > > > reclaim all unmapped pages. > > > > > > What you want here is a max_unmapped_ratio. > > > > > > > I thought about that, the logic for reusing min_unmapped_ratio was to > > keep a limit beyond which unmapped page cache shrinking should stop. > > Right. That is the role of it. Its a minimum to leave. You want a maximum > size of the pagte cache. In this case we want the maximum to be as small as the minimum, but from a general design perspective maximum does make sense. > > > I think you are suggesting max_unmapped_ratio as the point at which > > shrinking should begin, right? > > The role of min_unmapped_ratio is to never reclaim more pagecache if we > reach that ratio even if we have to go off node for an allocation. > > AFAICT What you propose is a maximum size of the page cache. If the number > of page cache pages goes beyond that then you trim the page cache in > background reclaim. > > > > > + reclaim_unmapped_pages(priority, zone, &sc); > > > > + > > > > if (!zone_watermark_ok_safe(zone, order, > > > > > > Hmmmm. Okay that means background reclaim does it. If so then we also want > > > zone reclaim to be able to work in the background I think. > > > > Anything specific you had in mind, works for me in testing, but is > > there anything specific that stands out in your mind that needs to be > > done? > > Hmmm. So this would also work in a NUMA configuration, right. Limiting the > sizes of the page cache would avoid zone reclaim through these limit. Page > cache size would be limited by the max_unmapped_ratio. > > zone_reclaim only would come into play if other allocations make the > memory on the node so tight that we would have to evict more page > cache pages in direct reclaim. > Then zone_reclaim could go down to shrink the page cache size to > min_unmapped_ratio. > I'll repost with max_unmapped_ration changes Thanks for the review! -- Three Cheers, Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>