| Date | Sun, 11 Jan 2009 00:43:52 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 04/16] dma-debug: add allocator code |
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* Joerg Roedel <joerg.roedel@amd.com> wrote:
> + printk(KERN_ERR "DMA-API: debugging out of memory " > + "- disabling\n");
btw., i'd suggest to not break kernel messages mid-string, but do something like this instead:
> + printk(KERN_ERR "DMA-API: debugging out of memory - disabling\n");
Also, i'd use WARN() - it might be useful to see what callsite depleted the pool.
> + entry = list_entry(free_entries.next, struct dma_debug_entry, list); > + list_del(&entry->list); > + memset(entry, 0, sizeof(*entry)); > + > + num_free_entries -= 1; > + if (num_free_entries < min_free_entries) > + min_free_entries = num_free_entries;
unlikely() i guess.
Regarding the entry pool locking:
> +static void dma_entry_free(struct dma_debug_entry *entry) > +{ > + unsigned long flags; > + > + /* > + * add to beginning of the list - this way the entries are > + * more likely cache hot when they are reallocated. > + */ > + spin_lock_irqsave(&free_entries_lock, flags); > + list_add(&entry->list, &free_entries); > + num_free_entries += 1; > + spin_unlock_irqrestore(&free_entries_lock, flags);
it might make sense to cache entries in the buckets - hence reuse the bucket spinlock. This means a somewhat higher effective pool size, but it also avoids a global lock.
Ingo
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