On Thursday 19 January 2006 06:22, Andrew Morton wrote: > david singleton <[email protected]> wrote: > > + if (mapping->robust_head == NULL) > > + return; > > + > > + if (list_empty(&mapping->robust_head->robust_list)) > > + return; > > + > > + mutex_lock(&mapping->robust_head->robust_mutex); > > + > > + head = &mapping->robust_head->robust_list; > > + futex_head = mapping->robust_head; > > + > > + list_for_each_entry_safe(this, next, head, list) { > > + list_del(&this->list); > > + kmem_cache_free(robust_futex_cachep, this); > > + } > > If we're throwing away the entire contents of the list, there's no need to > detach items as we go. Couldn't even detach the list elements first by list_splice_init(&mapping->robust_head->robust_list, head); and free the list from "head" after releasing the mutex? This would reduce lock contention, no? > > +#ifdef CONFIG_ROBUST_FUTEX > > + robust_futex_cachep = kmem_cache_create("robust_futex", sizeof(struct futex_robust), 0, 0, NULL, NULL); > > + file_futex_cachep = kmem_cache_create("file_futex", sizeof(struct futex_head), 0, 0, NULL, NULL); > > +#endif > > A bit of 80-column wrapping needed there please. > > Are futex_heads likely to be allocated in sufficient volume to justify > their own slab cache, rather than using kmalloc()? The speed is the same - > if anything, kmalloc() will be faster because its text and data are more > likely to be in CPU cache. The goal here was to do cheap futex accounting, as described in the documentation to this patch. Regards Ingo Oeser
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