Messages in this thread | | | Date | Tue, 4 Nov 2008 15:20:56 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [patch 1/7] cpusets: add dirty map to struct address_space |
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On Tue, 4 Nov 2008, Andrew Morton wrote:
>> +#ifdef CONFIG_CPUSETS >> +#if MAX_NUMNODES <= BITS_PER_LONG >> + nodemask_t dirty_nodes; /* nodes with dirty pages */ >> +#else >> + nodemask_t *dirty_nodes; /* pointer to mask, if dirty */ >> +#endif >> +#endif >> } __attribute__((aligned(sizeof(long)))); > > eek. Increasing the size of the address_space (and hence of the inode) > is a moderately big deal - there can be millions of these in memory.
Well this is adding only a single word to the inode structure.
>> @@ -72,6 +72,8 @@ struct writeback_control { >> * so we use a single control to update them >> */ >> unsigned no_nrwrite_index_update:1; >> + >> + nodemask_t *nodes; /* Nodemask to writeback */ > > This one doesn't get ifdefs?
The structure is typically allocated temporarily on the stack.
>> + nodemask_t *nodes = mapping->dirty_nodes; >> + int node = page_to_nid(page); >> + >> + if (!nodes) { >> + nodes = kmalloc(sizeof(nodemask_t), GFP_ATOMIC); > > erk, OK, called from __set_page_dirty, needs to be atomic. > > What are the consequences when this allocation fails?
Dirty tracking will not occur. All nodes are assumed to be dirty.
We discussed this earlier http://www.ussg.iu.edu/hypermail/linux/kernel/0709.1/2291.html
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