Messages in this thread | | | Date | Wed, 12 Feb 2020 14:52:47 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/slub: Detach node lock from counting free objects |
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On Sat, 1 Feb 2020 11:15:02 +0800 Wen Yang <wenyang@linux.alibaba.com> wrote:
> The lock, protecting the node partial list, is taken when couting the free > objects resident in that list. It introduces locking contention when the > page(s) is moved between CPU and node partial lists in allocation path > on another CPU. So reading "/proc/slabinfo" can possibily block the slab > allocation on another CPU for a while, 200ms in extreme cases. If the > slab object is to carry network packet, targeting the far-end disk array, > it causes block IO jitter issue. > > This fixes the block IO jitter issue by caching the total inuse objects in > the node in advance. The value is retrieved without taking the node partial > list lock on reading "/proc/slabinfo". > > ... > > @@ -1768,7 +1774,9 @@ static void free_slab(struct kmem_cache *s, struct page *page) > > static void discard_slab(struct kmem_cache *s, struct page *page) > { > - dec_slabs_node(s, page_to_nid(page), page->objects); > + int inuse = page->objects; > + > + dec_slabs_node(s, page_to_nid(page), page->objects, inuse);
Is this right? dec_slabs_node(..., page->objects, page->objects)?
If no, we could simply pass the page* to inc_slabs_node/dec_slabs_node and save a function argument.
If yes then why?
> free_slab(s, page); > } >
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