Messages in this thread | | | Date | Tue, 27 May 2014 14:17:59 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [PATCH 0/3] Shrinkers and proportional reclaim |
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On Tue, 27 May 2014, Dave Chinner wrote: > On Mon, May 26, 2014 at 02:44:29PM -0700, Hugh Dickins wrote: > > > > [PATCH 4/3] fs/superblock: Avoid counting without __GFP_FS > > > > Don't waste time counting objects in super_cache_count() if no __GFP_FS: > > super_cache_scan() would only back out with SHRINK_STOP in that case. > > > > Signed-off-by: Hugh Dickins <hughd@google.com> > > While you might think that's a good thing, it's not. The act of > shrinking is kept separate from the accounting of how much shrinking > needs to take place. The amount of work the shrinker can't do due > to the reclaim context is deferred until the shrinker is called in a > context where it can do work (eg. kswapd) > > Hence not accounting for work that can't be done immediately will > adversely impact the balance of the system under memory intensive > filesystem workloads. In these worklaods, almost all allocations are > done in the GFP_NOFS or GFP_NOIO contexts so not deferring the work > will will effectively stop superblock cache reclaim entirely....
Thanks for filling me in on that. At first I misunderstood you, and went off looking in the wrong direction. Now I see what you're referring to: the quantity that shrink_slab_node() accumulates in and withdraws from shrinker->nr_deferred[nid].
Right: forget my super_cache_count() __GFP_FS patch!
Hugh
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