On Tue, Sep 03, 2019 at 10:02:59AM +0300, Andriy Gapon wrote: > On 02/09/2019 01:22, Mark Johnston wrote: > > Author: markj > > Date: Sun Sep 1 22:22:43 2019 > > New Revision: 351673 > > URL: https://svnweb.freebsd.org/changeset/base/351673 > > > > Log: > > Extend uma_reclaim() to permit different reclamation targets. > > > > The page daemon periodically invokes uma_reclaim() to reclaim cached > > items from each zone when the system is under memory pressure. This > > is important since the size of these caches is unbounded by default. > > However it also results in bursts of high latency when allocating from > > heavily used zones as threads miss in the per-CPU caches and must > > access the keg in order to allocate new items. > > > > With r340405 we maintain an estimate of each zone's usage of its > > (per-NUMA domain) cache of full buckets. Start making use of this > > estimate to avoid reclaiming the entire cache when under memory > > pressure. In particular, introduce TRIM, DRAIN and DRAIN_CPU > > verbs for uma_reclaim() and uma_zone_reclaim(). When trimming, only > > items in excess of the estimate are reclaimed. Draining a zone > > reclaims all of the cached full buckets (the previous behaviour of > > uma_reclaim()), and may further drain the per-CPU caches in extreme > > cases. > > > > Now, when under memory pressure, the page daemon will trim zones > > rather than draining them. As a result, heavily used zones do not incur > > bursts of bucket cache misses following reclamation, but large, unused > > caches will be reclaimed as before. > > Mark, > > have you considered running UMA_RECLAIM_TRIM periodically, even without a > memory > pressure? > I think that with such a periodic trimming there will be less need to invoke > vm_lowmem(). > > Also, I think that we would be able to retire (or re-purpose) lowmem_period. > E.g., the trimming would be done every lowmem_period, but vm_lowmem() would > not > be throttled. > > One example of the throttling of vm_lowmem being bad is its interaction with > the > ZFS ARC. When there is a spike in memory usage we want the ARC to adapt as > quickly as possible. But at present the lowmem_period logic interferes with > that.
Some time ago, I sent Mark a patch that implements this logic, specialy for ARC and mbuf cooperate. Mostly problem I am see at this work -- very slowly vm_page_free(). May be currenly this is more speedy... _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
